Suitability of various materials with the perovskite and K₂NiF₄ structures as substrates for the epitaxy of high temperature superconductors (HTSC) and manganite perovskites with colossal magneto resistance (CMR) is studied. In particular, the analysis concentrates on solid solutions in LaGaO₃-NdGaO₃ and SrLaGaO₄-SrLaAlO₄ systems. The aim of the present investigation is to test the possibility of obtaining LaGaO₃-NdGaO₃ solid solutions with cubic structure. Single crystal growth of LaGaO₃-NdGaO₃ solid solutions in a selected NdGaO₃ concentration range has been investigated. It allows us to estimate the segregation coefficient for Nd in La_1-xNd_xGaO₃. Unit-cell parameters as a function of composition have been determined. Single crystal growth of SrLaGaO₄-SrLaAlO₄ solid solutions has also been investigated. The optimum starting melt composition, the segregation coefficients for Ga in SrLaAlO₄ and Al in SrLaGaO₄ as well as the unit-cell parameters as a function of composition have been determined. Both LaGaO₃-NdGaO₃ and SrLaGaO₄-SrLaAlO₄ solid solutions are suitable substrate materials for HTSC and CMR perovskite epitaxy. Since their lattice parameters can smoothly be adjusted to those of deposited layers, the presented solid solutions are attractive substrate materials with tunable lattice parameters.

The growth of the single crystals of ZnTe and Cd_1-xZn_xTe (x <EQ 0.25) by a simple, horizontal, low temperature physical vapor transport technique (PVT) is presented as an example of the application of the PVT technique to the technology of MBE substrates: large (1 inch in diameter), twin-free crystals of wide-gap II-VI compounds of very high quality. The advantages of the PVT technique are emphasized. The results of the characterization of the grown crystals are presented.

High temperature solution growth of oxide single crystals has become very useful method in investigations of new classes of materials for opto-electronics. In this paper applicability of this method, its advantages, and disadvantages have been discussed. Investigations of crystallization of several oxides such as mixed sillenites Bi₁₂Ti_1-xM_xO₂₀ (M equals Pb, Ga, V), double tungstates (K_1-xCs_xDy(WO₄)₂ and KGd(WO₄)₂:Nd), and borates (CsLiB₆O₁₀ and YAl₃(BO₃)₄:Nd) carried out by this technique have been described.

Recent studies of the structural and magnetic properties of spin-ladder compounds will be reviewed. The spin ladders of the composition (M₂Cu₂O₃)_m(CuO₂)_n (where M are divalent and trivalent cations) have both CuO₂ ribbons and Cu₂O₃ two-leg ladders. Both of the building blocks show spin gaps in their excitation spectra which originate from a dimerized state. In the reviewed systems it is possible to change the number of hole carriers by changing the ratio Ca/Sr. The hole carriers are considered to be localized in the chains (ribbons) and are coupled with the copper spins forming the Zhang-Rice singlets. The dimers are formed between next-nearest neighbor copper ions. The charge ordering involving both dimerization and the Zhang-Rice singlet formation is suggested to exist in (M₂Cu₂O₃)₅(CuO₂)₇ compounds. In some compounds with high Ca/Sr ratio and with substantial hole transfer from ribbons to ladders the superconducting state is created with a high critical temperature (of about 80 K).

Synthesis of LnMoO₄-type molybdates for the entire rare earths row was carried out in a vacuum furnace at 1400 degree(s)C during 20 hours using Ln₂MoO₆ and MoO₂. The obtained molybdates in the Ladivided byNd row crystallize in cubic syngony, europium molybdate EuMoO₄--in tetragonal syngony, LnMoO₄ molybdates for Sm, Gddivided byLu, Y--in monoclinic symmetry. LnMoO₄-type molybdates are stable up to 210 - 270 degree(s)C. The main oxidation occurs at 600 degree(s)C. Investigation of interaction processes between LnMoO₄ and chlorine was carried out using a special- purpose set-up. Our results show that LnMoO₄ interaction with chlorine occurs in 600 - 750 degree(s)C temperature range. The obtained rare earth oxochloromolybdates are close in their structure to that of gadolinium oxochlorotungstate GdWO₄Cl, and crystallize in monoclinic syngony. The decomposition process of TR oxochloromolybdates begins at 600 degree(s)C. Interaction of LnMoO₄ (Ln equals La, Nd, Gd, Dy, Er) with sulphur was studied at 600 and 1000 degree(s)C. The ratio LnMoO₄:S was 1:1. The specimen of GdMoO₄+S composition is homogeneous and has scheelite-type structure with unit cell parameters a equals 5.2023 angstroms, c equals 11.1960 angstroms. Increasing of quenching temperature for LnMoO₄ with S up to 1000 degree(s)C leads to the description of primary crystal structure of molybdates.

(beta) ₁-CuZnAl single-crystals were subject to uniaxial tension with subgrain boundaries parallel to the direction of tension. A relation between individual stages of martensite (gamma) '₁ single-crystals formation and changes of mechanical stress was determined. The stress was assessed on the basis of diffraction reflexes half-width measurement, measured on a Bond diffractometer, that ensured a precise assessment of even minute changes.

Crystals of LaGaO₃ were grown by the Czochralski method using seeds with different orientations. Crystal structure of LaGaO₃ is orthorombic at room temperature and rhomohedral above 425 K. Owing to the phase transition the crystals are twinned and the density of twins depends on the seed quality and orientation as well as on purity of starting materials. Two boules of LaGaO₃ containing 0.1 at% and 0.3 at% of Cr³⁺ were pulled using seeds with <112> orientation. Absorption and emission spectra are consistent with a strong crystal field case in which the ²E state is the lowest. At room temperature the luminescence consists of a broad vibronic band stretching from about 12700 cm^-1 to 15000 cm^-1. At low temperature the phonon side band disappears and two sharp R₁ and R₂ lines can be located. Additional sharp line in spectra has been attributed to the transition of coupled Cr³⁺ pairs.

The mixed La_xRE_1-xF₃ (RE equals Ce, Pr, Nd) single crystals doped with Gd³⁺ (0.1 mol%) were grown by a modified Bridgmann-Stockbarger method using an induction furnace. The quality of crystals were controlled by X-ray diffraction and EPR technique, in addition the observation of defects with the polarizing microscope after chemical etching with acid was performed. The behavior of surrounding Gd³⁺ ions in hexagonal matrices was investigated at different temperatures (4.2 - 300 K), analyzing EPR data in the light of the superposition model. The distortion of the site symmetry of Gd³⁺ ions from the C_2v towards C₂ was observed in La_0.9Nd_0.1F₃ at 4.2 K. The low temperature magnetic ordering was determined to be antiferromagnetic (T_N equals 0.4 K for NdF₃ and T_N equals 0.03 K for La_0.9Nd_0.1F₃ using the molecular field theory).

TAG fibers were grown by the micro pulling down method from stoichiometric and alumina rich melts. Using the Czochralski technique polycrystalline TAG samples were obtained from alumina rich melts. It was shown that both growth methods the crystallization of TAP can be avoided by starting from a melt concerning less than 32 mol-% Tb₂O₃.

The phase diagram of the Li-V-O system was investigated to find the best conditions for the crystal growth of S equals 1/2 1D system (gamma) -LiV₂O₅. Basing on the obtained phase diagram a single crystal with dimensions 18 X 3 X 2 mm³ was successfully grown from a liquid phase using LiVO₃ as a flux. A bigger single crystal of the spin-Peierls system (alpha) '-NaV₂O₅ with dimensions 18 X 6 X 2 mm³ was obtained by a similar method. The crystals of Li (Na) deficient samples were also prepared. Magnetic and electric properties of these crystals were investigated.

The chalcopyrite n-type AgInS₂ crystals have been grown by the Bridgman method from the melt containing stoichiometric quantities of components with 0.2% excess of In or 0.1% excess of S. The steady-state photoconductivity and photoconductivity decay have been measured from T equals 90 to 360 K. At high light intensities the photoconductivity depends sublinearly on excitation strength in a power 0.5. In this excitation strength range the decay of photoconductivity with time curves have `hyperbolic shape' which is typical for the quadratic recombination process.

The growth of KDP crystals from solution is studied in coherent light with an optical apparatus called Diffrasor. It is aimed to study interface phenomena during crystal growth from fluid phases, mostly from solution. It provides data about concentration gradients inside the fluid by measuring the deflection occurring in a laser beam which crosses the solution during crystal growth. It may investigate layers of fluid over the crystal faces, as thin as 2 microns. Diffrasor improves the knowledge about the boundary layer and the intermediate state of matter between the completely fluid solution and the fully solid crystal. Besides, this apparatus is simple enough to be devoted also to material sciences research in microgravity.

Multidirectional HOlographic Interferometer (MHOI), a non- invasive diagnostic tool to monitor 3D concentration fields during crystal growth from solution, is applied to study the diffusion fields near the monocrystals of potassium dihydrogen phosphate growing in gel and solution. In contrast with other existing holographic interferometers, MHOI uses optical fibers in six optical circuits, realizing for the first time the hardware of an optical tomograph. The system allows us to obtain the data required to get real 3D reconstruction of diffusion fields.

Experimental measurements of the solubility of fluorene in six halogen derivative solvents are reported for the temperature range 288 K - 323 K. The results have been correlated by using the Weimer-Prausnitz equation and the experimental activity coefficients ((gamma) _s^WP) obtained have been compared to the values predicted by Scatchard-Hildebrand regular solution theory. When the binary parameter, I_s,solv, determined from the lowest solubility datum point temperature is used in the Scatchard- Hildebrand equation, the activity coefficients ((gamma) _s^SHE) are predicted to within an average of 0.64%. The regular behavior of the solutions has been confirmed by the excess entropy of mixing ((Delta) S^E approximately equals 0) and the enthalpy of mixing ((Delta) H^M_SHE > 0). Based on the solubility ratios calculated from the solubility data, the ranges of temperature for good growth of fluorene crystals have been estimated.

Velocity of ultrasonic waves, as a function of temperature and concentration have been measured for four naphthalene halogen derivative solutions in supersaturated metastable regions, under conditions of continuous linear cooling and without stirring. The maximum undercooling (Delta) T_max was evaluated as a difference between saturation temperature and the temperature of first precipitation detected by the change of ultrasonic velocity. It was found that for all the solutions in their metastable regions, ultrasonic velocity linearly increases with decreasing temperature at given concentration and that the first-order equations relating ultrasonic velocity with solutions concentration can satisfactorily be used to describe the data.

Ionic conductors are of tremendous importance for numerous and various applications from the fields of batteries up to sensors. The aim was to enlarge their potentialities by creating new families of compounds having such properties. Our researches have been focused on oxides containing both M transition elements (M equals Mo, V, Nb) and `lone pair oxides', i.e. from M* elements like M* equals Sb III, Te IV, Bi III, characterized by a ns² electronic state involving a lone pair E of electrons. Some new compounds will be presented and their particular atomic structures depicted.

Every complete lattice theory of solid state consists of two basic elements, namely the description of the interatomic forces and the theory connecting them with the dynamical and thermodynamical properties of the crystal. In the present paper we have discussed the application of the self- consistent phonon theory formulated independently by various authors with the help of the modern techniques of many-body method to the quantum crystals. The results of theoretical investigations of the high-temperature and pressure properties of solid b.c.c. ³He, h.c.p. ⁴He and f.c.c. ²⁰Ne in terms of the interatomic potential energy curves proposed by Beck, Murrel-Shaw, Morse, Buckingham and Lennard-Jones are given and compared with available experimental data. Extensive comparison of theoretical and experimental results allows us to discuss the suitability the above self-consistent potential energy functions as real interatomic potential modes in solid helium and neon.

Applications of the bond polarizability model to various nonlinear phenomena in crystals are shown. Special attention is paid to second harmonic generation, nonlinear refractive index and hyper-Raman scattering.

The main methods and models for studies of the phonon spectra of crystals are recalled together with the approaches used to get reliable interionic interaction parameters. Recent results concerning interionic potentials are shown. Examples of applications of the lattice dynamical modelizations are given in the case of perovskites-related structures exhibiting displasive and martensitic transitions, and ionic conductivity.

High effect measurements were carried out in the 500 - 1200 K temperature range under controlled Cd vapor pressure (P_Cd equals 10^-5-3 atm). Samples' saturation by In was performed from the vapor phase at 1073 K under P_In during 24 or 240 hours. The In concentration in the sample was about approximately 10¹⁹ and approximately 10²⁰ at/cm³ respectively. Up to 500 K and P^max_Cd the electron concentration [e^-] in the heavy doped samples is temperature independent, it is characterized by the slope (Delta) E equals 0.4 eV and reaches the maximum value of approximately 3 X 10¹⁸ at/cm³. The temperature dependence in the sample, containing approximately 10¹⁹ at/cm³ In, has a maximum ]e^-] value and then decreases. The results can be described by a defect structure model, supposing, that the dominating defects are In⁺_Cd defects and complex associates of the (In⁺_Cd V^2-_Cd)^- type, but an essential role play V^2-_Cd and the increase of In solubility with temperature also.

GaSb crystals highly doped with tellurium were grown using the Czochralski method without encapsulant in the flowing atmosphere of ionized hydrogen. The inherent free carrier concentration was several times lower than by using the molecular hydrogen. It was shown that the ionized atmosphere served as a passivator in the wider range of tellurium concentration and that the equilibrium between passivated and active donors was created according to the ratio of p- to n-type dopants in the starting melt.

Gallium antimonide (GaSb) crystals were grown by the Czochralski method in a flowing hydrogen atmosphere and doped with various elements. The limit of a doping concentration of each used dopant was measured. It was shown that the lowest solubility was for S, N, Cu and the highest solubility for In, Ge, Te and As. The results are discussed and summarized in the table.

In a composite of liquid dielectric with granular conducting dopant in a form of a micrometer particles of conductor one observes the structure ordering process due to external electric field, manifesting by the increase of observed electrical conductivity. The mechanism of such ordering is similar to the phenomena occurring in the electrorheological liquids. By application of the conductor particles as an active polar dopant, the observed ordering effects take place at lower values of the electric field, compared with the ordering case of the granular dopants of an insulator. A simple theoretical description of the above mentioned phenomena was developed. They are attributed to the mutual interaction of conducting particles, having the field- induced dipole moments. The measured current increase is due to the power dissipation in the sample, related to the particle motion in viscous medium, as well as to the increase of sample capacitance. The ordering effect of such a medium consists in the mutual electrostatic interaction of the electric dipoles, induced in the dopant particles, as well as in the buildup of a linear or dendritic spatial structures with a symmetry determined by the direction of the external electric field.

Monte Carlo simulations with the use of a new, efficient algorithm have been performed for a wide range of supersaturation values. The influence of both the method of calculation of the average growth rate and the size of an array on the simulation results are analyzed. It is revealed that calculations of the average growth rate without the use of explicitly defined growth time lead to systematic errors and inconsistency with observed growth process, especially at low supersaturations. On the other hand, the size of an array affects not only value of the average growth rate but also operating growth mechanism. Therefore, the average growth rate increases non-linearly with increasing size of an array, tending to a constant value. This effect has been observed for growth of a perfect face as well as for growth of a face consisting steps.

The subject of this paper is an analysis of the kinetic conditions corresponding to changes in habits of 2D crystal depending on time-constant growth rates of individual faces. Such analysis is possible based on the previously derived set of equations describing different quantities, for example the rate of changes in size of a given face. Applying this set of equations to exemplary chosen crystal obtained artificially-potassium bichromate proves that the presented formulae may be used as a tool for precise crystal growth process analysis and can help in better understanding the physical background of many phenomena encountered during crystal growth process and influencing crystal morphologies.

Recently increasing interest in In or Ga doped CdMnTe, ternary semimagnetic semiconducting compound, has been observed due to the persistent photoconductivity (PPC) effect observed in the material and subsequently possible application of the material as volume holographic gratings. DX-like centers existing in the material are responsible for the PPC effect: they exhibit shallow-deep metastability due to strong interaction with surrounding lattice. DX centers have been observed in In doped CdTe, CdMnTe and CdMnTeSe. In this paper we present our results of DLTS study in indium doped Cd_0.8Mn_0.2Te. In the material five electron traps designated by us as E1-E5 were observed with activation energies equal to 0.23 eV, 0.28 eV, 0.38 eV, 0.48 eV, and 0.65 eV, respectively. For one of them, E3, a very strong temperature dependence of capture cross section is observed. Therefore related defects exhibit large lattice relaxation which can be responsible for the photomemory effect observed in the material.

Measurements of high-temperature electrical properties ([e^-], (mu) , (sigma) ) were performed using Bridgman grown Ge-doped CdTe single crystals. The isothermal (873, 973, 1073 K) carrier concentration dependences under different Cd vapor pressure and temperature dependences of carrier concentration were investigated. The experimental results were compared with those for pure CdTe single crystals. The analysis of the obtained results agrees with the model of amphoteric behavior of Ge in CdTe under chosen conditions (high P_Cd value and temperature 1073 K).

The theoretical considerations concerning the elastic properties of the anisotropic crystals, assuming harmonic approximation are presented. In the model proposed the range of the elastic interaction, restricted to the participation of the nearest neighbors is represented as a continuum sensitive to the influence of the molecular electromagnetic field of the next neighbors. This approach to the problem has been adapted to the description of the elastic properties of the conducting and dielectric crystals.

Theoretical studies of lattice dynamics of arsenic, antimony and bismuth are presented. A model of covalent bonds and a phenomenological model of potential of interatomic forces are applied in these studies. The parameters of the potential are estimated from experimental data of the phonon dispersion relations.

The name `quantum crystals' is used for solids with large zero-point energy. The solidified rare gases like solid helium and neon are the most conspicuous examples of this class of materials. In this paper the results of theoretical investigations of interatomic interactions and physical properties of quantum crystals within the self-consistent phonon theory are presented. The description of the interatomic forces and the theory connecting them with the dynamical and thermodynamical properties of solid ⁴He and Ne are given in terms of the (exp,m) Buckingham, (n,m) Lennard-Jones and the (exp,exp) Morse pair potentials. Calculating the dynamics of crystal lattice and the thermodynamical properties of h.c.p. ⁴He and f.c.c. Ne tests relative merits of these potential functions and allows to compare them with the experimental data.

In this paper we study the problem of lattice stability of the heavier rare gas solids (i.e. Ar, Kr, Xe) in terms of the reduced second-order self-consistent approximation, developed by Plakida and Siklos on the basis of the double- time Green's functions method. As a model of interatomic interactions we take the (n,m) Lennard-Jones, (exp,m) Buckingham and (exp,exp) Morse pair potentials with the parameters determined self-consistently with the help of the experimental data for the zero-point lattice constant, energy of sublimation and isothermal compressibility. Apart from the pressure variations of the limiting temperature of stability we also investigate the behavior of selected thermodynamical properties of crystal near the limit of stability. The mentioned theoretical results are compared with available experimental data.

Transmission Line Matrix is a numerical technique which models physical phenomena by the establishment of analogues with electrical networks which include transmission lines. These enforce time discretization. There have been many significant developments in this rapidly expanding field. This paper discusses the formulation of algorithms in the areas of: semiconductor carrier transport, crystallization, chemical kinetics and effective bounding of very large models.

Fractional thermoluminescence (FTL) is computer simulated using a model of an insulator with three kinds of active traps and one kind of recombination center. The trap depth values are determined from the calculated FTL curve using Gobrecht and Hofmann method modified by Chruscinska. The method yields the correct trap energy spectrum if the thermoluminescence curve having weakly overlapping peaks is analyzed. The trap depths determined with this method have values lower by about 10 to 25% than those used for the calculations.

An accuracy of the initial rise method is considered, as applied to the determination of the activation energy from thermoluminescence and thermally stimulated conductivity spectra. The method is analyzed in the classical case described by the simple trap model as well as in the presence of spatial correlation between traps. For this purpose a novel, generalized version of the Monte Carlo algorithm was developed. It allows to simulate TSR processes with an arbitrary heating function applied that gives the possibility of simulating the use of the initial rise method and the fractional glow technique. An influence of initial filling of traps on the initial rise method is analyzed. It is confirmed that for sufficiently low initial concentration of charge carriers in traps the method gives correct values of the activation energies even in the case of strong retrapping. This conclusion is valid irrespective of the spatial correlation between traps and recombination centers.

Curve fitting algorithms are widely used for the determination of trap parameters from thermoluminescence (TL) glow curves. Most of the algorithms are based on the general order kinetics (GOK) model. In this paper, we study the accuracy of GOK model in application to the analysis of TL curves. It is shown that in many cases especially characterized by high retrapping coefficients, the GOK model is not applicable giving erroneous estimation of the activation energy. To overcome the difficulty a novel fitting algorithm is suggested based on the quasi equilibrium approximation. The algorithm allows to analyze a single TL peak as well as to deconvolute complex TL curves. Using numerically generated TL spectra the preciseness and stability of the method is verified.

Fourteen methods of the trap depth determination from the thermoluminescence (TL) curves have been examined by applying these methods to numerically calculated TL curves. The heating-rate methods of Hoogenstraaten, Haering and Adams, Chen and Winer, and Opanowicz yield the correct values of trap depths.

Following Volkenstein's idea the density of conformon states (rho) (E) is investigated. Using the path-integral method in conditions of the strong conformational disorder the numerical account (rho) (E) is carried out. The results of account (rho) (E) under the new formula are discussed.

The review of the elastic and elastooptic properties of SrLaAlO₄ and SrLaGaO₄ single crystals grown by Czochralski method is presented. After a brief description of the Brillouin scattering method, used in the characterization of the elastic and elastooptic properties, the experimental results obtained for SLA and SLG single crystals by this method are surveyed. The influence of the annealing process of SLA and SLG single crystals at different temperature and atmosphere conditions on their elastic and elastooptic properties are also presented. Obtained results are discussed in terms of the nature of the oxygen point defects which might be created during the crystal growth process.

Wide gap II-VI mixed crystals containing Mg and Be are recently studied extensively for their application in constructing blue-green laser diodes. This work deals with experimental study of optical modes in Zn_1-xMg_xSe and Zn_1-xBe_xSe semiconductors using Raman scattering method. Measurements have been performed at room and liquid nitrogen temperatures for Zn_1-xMg_xSe crystals with Mg content in the range 0 < x < 0.34 and for Zn_1-xBe_xSe with Be content in the range 0 < x < 0.26. From polarized Raman spectra longitudinal and transverse optical modes corresponding to ZnSe- and MgSe-like modes in Zn_1-xMg_xSe and to ZnSe- and BeSe-like modes in Zn_1-xBe_xSe were determined. These lattice vibrations can be described by the modified random element isodisplacement model.

This work presents results of investigations of photoluminescence and structural properties of ternary Zn_1-xBe_xSe, Cd_1-xMg_xSe, Zn_1-xMg_xSe and quaternary Cd_1-x-yMg_xZn_ySe, Zn_1-x-yBe_xMg_ySe, Zn_1-xMg_xSe_1-ySe_y mixed crystals. These crystals were grown from the melt by the high-pressure Bridgman method. Zn_1-xMg_xSe and Zn_1-xSr_xSe were also obtained by annealing of ZnSe crystals in evacuated quartz ampoules containing Mg or Sr metal. It has been found that admixing of Mg into ZnSe favors the formation of wurtzite Zn_1-xMg_xSe while Be-sphalerite Zn_1-xBe_xSe structures. Low temperature (40 K) photoluminescence spectra consist of exciton, edge and deep levels emission bands. For most of investigated crystals the emission corresponding to the highest photon energy line in luminescence spectrum is observed up to room temperature.

The effect of annealing at <EQ 1000 K under enhanced argon pressure, HP, up to 1.6 GPa on photoluminescence, PL, and electrical properties of Cz-Si was investigated. The PL lines, related to presence of thermal donors, TDs, were detected at 2 K at (1.08 - 1.09) eV for the samples with interstitial oxygen concentration, c_o, in the (8 - 11) X 10¹⁷ cm^-3 range, treated at 720 K - HP, whereas at 300 K the PL band at about 0.79 eV was observed. The 0.79 eV PL band intensity increased with c_o but decreased with HP; the treatment at HP - 720 K for 10 h of the samples with before-created TDs also resulted in decreased intensity of the 0.79 eV band PL at 0.9 eV was observed at 2 K for the sample pre-annealed at 1000 K and afterwards pressure-treated at 920 K - 1.6 GPa, whereas at 300 K, this sample indicated the broad Pl peak at 0.86 eV. Presence of `additional' defects in Cz-Si (introduced by hydrogen implantation) caused suppression of PL after annealing at 720 K -10⁵/1.2 X 10⁹ Pa for 10 h, whereas the hydrogen plasma etched samples indicated detectable band-to-band PL at about 1.1 eV. Qualitative explanation of observed effects was proposed.

The processes of gradual degradation as well as the destruction processes of high power electron beam pumped lasers have been studied. The main reason of gradual degradation has been shown to be the increase of dislocation density due to thermoelastic stresses caused by both electron beam treatment and own laser radiation. The types of macrodefects which are responsible for laser screen destruction have been identified. CdS crystals obtained by the method developed by us were shown to have the highest optical strength.

Previous measurements of quadratic electrooptic coefficients in the KDP family of crystals have been analyzed. In addition, the quadratic electrooptic coefficient n_o³g₁₁₁₁-n_e³g₃₃₁₁ of KDP and ADP has been measured by means of the dynamic polarimetric method. The results obtained confirm that quadratic electrooptic coefficients of KDP-type crystals are of the order of magnitude of 10^-20 m²V². This is about 100 times smaller than values widely cited in the literature obtained by other authors employing the static polarimetric technique.

Infrared absorption spectroscopy has been used to study the vibrational modes in various borate crystals, the electronic transitions of Nd³⁺ ions in NYAB, and the stretching vibration of hydroxyl ions in CLBO crystals.

Optical properties of some mixed B₁₂TiO₂₀ (BiTiO) and Bi₄₀Ga₂O₆₃ (BiGaO) single crystals were investigated. The mixed single crystals have been grown with use of Top Seeded Solution Growth technique and Ti ion was substituted with V, Pb or Ga ions. Thermal conditions enabling growth of uniform [110] BiTiO and BiGaO single crystals with totally flat (110) interface have been found. Special interest was devoted to the problem of photochromic effect existing in investigated single crystals at temperatures lower than 200 K. The characteristic temperature of thermal bleaching and the wave length active in a coloring process (the coloring spectra) for all mixed single crystals were established. It was noticed that the substitution of some ions in tetrahedral positions had essential effect on photochromic properties of investigated mixed sillenites. In this case the photochromic effect should be related to the fundamental edge shift.

Thermal stability of photochromic effect existing at temperatures below 100 K in scandium doped germanium sillenites (BGO:Sc) was investigated. The single crystals of sillenites were obtained by the Czochralski technique. Some thermally stimulated processes related to the photochromic properties of doped sillenites were noticed. Process of thermal bleaching was studied in a wide spectral range and in various conditions. Both equilibrium thermal bleaching and non-equilibrium one leading to so called thermoabsorption were intensively studied. On the base of proposed model of thermoabsorption the energies of trap centers were calculated. It has been shown that some optical properties of sillenites are very sensitive to the procedure and conditions in which the coloring process was provided.

In this work we investigate spectroscopic properties of Cr³⁺ and Cr³⁺ - Nd³⁺ interaction in LiTaO₃ using optical absorption, luminescence and luminescence decay times at temperatures between 5 K and 300 K. Some preliminary data obtained with singly doped LiTaO₃:Cr at low activator concentration are given in our previous work. Recorded spectra indicate that both the Cr³⁺ and Nd³⁺ are located in several non- equivalent sites which differ in the strength of the crystal field. Luminescence spectrum of Cr³⁺ consists of a broad band whose maximum and intensity depend on temperature. Below about 50 K an additional sharp band with four distinct components appears in the spectrum. The broad band attributed to the spin allowed ⁴T₂ - ⁴A₂ transition of Cr³⁺ ions overlaps two absorption bands of Nd³⁺ ions at about 810 nm and 890 nm making the Cr³⁺ - Nd³⁺ energy transfer process feasible. Results of measurements are discussed and compared to those obtained with LiNbO₃:Cr.

In this paper the study of SrLaGaO_3+(delta ) (SLG) and SrLaAlO_3+(delta ) (SLA) crystals using Raman scattering method is presented. The Raman scattering spectra of SLG and SLA crystals for different scattering geometries were obtained in the temperature range from 50 K to 300 K. The temperature dependencies of the Raman intensity, Raman shift and FWHM some of the Raman bands were investigated. The obtained results are discussed in terms of the nature of point defects, which might arise in the ABCO₄ lattice during the crystals growth process.

The n-CuInS₂ crystals were grown from the In-rich melt of Cu, In, and S compounds using the Bridgman method. The crystals were grown at two different cooling rates (crystals I and II). The crystals I show two types of temperature dependence of the electron mobility related to different temperature ranges ((mu) _o approximately T^3/2 and (mu) _o approximately T^3/2) connected with the impurities and phonons scattering of electrons. The electron mobility of the crystals I is independent of the illumination with white light. On the other hand, the crystals II show strong temperature dependence of the electron mobility ((mu) _o approximately T^5/2), which changes drastically its character ((mu) approximately T^3/2) when illuminated with white light.

The main absorption spectra and the main refractive indices of the AD_y(WO₄)₂ (where A equals K, Rb,) single crystals have been investigated. The existence of three different spectra (trichroism) along the three optical axes of the crystals have been revealed. Using optical microscopy method main refractive indices have been found.

The investigations of the Raman scattering spectra of the KDy(WO₄)₂ single crystals have shown that the phase transitions found at 6.38 K exhibit the peculiarities characteristic of SPT Jahn-Teller type. The paper presents also the results of IR absorption investigations of the ADy(WO₄)₂ single crystals, where A equals K, Rb.

The investigations of the optical absorption spectra of the ADy(WO₄)₂ (where A equals K, Rb,) single crystals have shown that the phase transitions found at 6.38 K for KDy(WO₄)₂, 4.9 K, 9.0 K for RbDy(WO₄)₂, exhibit the peculiarities characteristic of structural phase transition of Jahn-Teller type. The paper presents also the results of VIS absorption investigations of the K_(1-x))Cs_xDy(WO₄)₂ mixed single crystals.

A series of V_2-xMo_xO₅ (x equals 0.2, 0.4, 0.6, 0.8) samples has been investigated by X-ray photoelectron spectroscopy (XPS). MoO₃, VO₂, V₂O₅ (powders), VO₂^(c) and Na_0.33V₂O₅^(c) have been used as reference samples. According to the XPS measurements, the valence of Mo atoms in this series is not changed during the Mo doping and it is close to that of MoO₃. The V atoms show a mixed valence in the V_2-xMo_xO₅ system: with increasing of the Mo content, a higher concentration of tetravalent V atoms is observed. For one sample of this series, V_1.2Mo_0.8O₅, it was found that the XPS valence band and also the core level spectra are close to those of another mixed- valence system, Na_0.33V₂O₅. Both compounds show similar electrical properties, which can be interpreted in terms of a two-level hopping model. It is concluded that the impurity states in the band gap of both compounds have 3d like character and they are formed at the expense of the additional electrons of Mo or Na.

The Raman spectra of Gly(DOT)H₃PO₃ were investigated over the internal frequency range 400 - 3200 cm^-1. The measurements have been performed in the temperature range 175 - 250 K covering paraelectric-ferroelectric P2₁/a-P2₁ phase transition. The Raman study revealed the dynamical disorder of protons which is coupled to the motions of glycinium cations. Two types of glycinium cations were observed in the ferroelectric phase instead of one in paraelectric phase. The obtained results confirm the order- disorder nature of a proper ferroelectric phase transition of second order.

Measurements of magnetization versus temperature and magnetic field have been performed on single crystals of Bi₂Sr₂CaCu₂O_y irradiated by fast electrons in temperature range from 4.2 K to 80 K and at magnetic field up to 6T. The critical current density under irradiation by fluence of 2 X 10¹⁸ cm^-2 (E equals 4 MeV) is enhanced by 1.3 times and amounts to 1.3 X 10⁶ Acm^-2 at 4.2 K and zero magnetic field (H (parallel) c). At high temperatures the dependence of the irreversibility field B_irr(T) is described by linear expression. However, at temperature decreasing B_irr increases very abruptly near 20 K - 30 K. For irradiated state the irreversibility line shifts towards higher magnetic fields and B_irr changes drastically near 20 - 25 K. The results can be account for by the model of a crossover from 3D to 2D pinning.

Single crystals of PrBa₂Cu₃O_7-(gamma ) have been grown from BaO-CuO solutions. The influence of the post-growth treatment (reduction, oxidation, cooling) on some structural, electrical and magnetic properties of obtained crystals was examined. We report the observation of inhomogeneous superconductivity of PrBa₂Cu₃O_7-(gamma ) crystals after the high temperature reduction in Ar and typical for 1:2:3 compounds oxidation process from the ac magnetic susceptibility and resistivity measurements.

We report the experimental results of ballistic electron transport in point contact junctions between normal metal and high temperature superconductors. The conductance- voltage characteristics in Ba₂Sr₂CaCu₂O₈ and YBa₂Cu₃O_7-(gamma ) are proved to show the superconducting gap structure. The features of the spectra observed at eV approximately 2(Delta) which showed zero-bias conductance peak are also discussed.

We report on the temperature and pressure dependences of the magnetization in the KDy(WO₄)₂ single crystal. The directions of magnetic axes in the crystal under study were established. It has been shown that at the point of the structural phase transition the Curie-Weiss temperature changes considerably. Under pressure of about 0.8 GPa the temperature of the structural phase transition increases nearly by a factor of two. As a result of the pressure effect the low temperature phase area is expanded.

Growth conditions for Nd:YVO₄ crystals and some optical properties are presented. The obtained Nd:YVO₄ crystal shows lower content of point defects and consequently, lower susceptibility to ionizing radiation. ESR measurements show the presence of V ions in interstitial sites with another than 5t valency. Obtained by Czochralski method crystals reveal very good optical properties, some of which are better than for Nd:YAG.

In this work we present results on YAG:V³⁺ single crystal growth and examination for the purposes of Q- switching of laser resonator in the near IR band. A number of YAG single crystals doped with different concentrations of V³⁺ ions were obtained by the Czochralski method. The absorption and emission spectra measurements on those crystals are presented. After crystal growth only a small part of vanadium atoms is introduced into a crystal structure as V³⁺ ions in tetrahedral positions, the other ones are at different positions or at higher charge states V⁴⁺ and V⁵⁺. Receiving of vanadium ions of V³⁺ valency in the desired points of YAG structure can be possible as a result of complex reactions in solid- state phase. Such reactions proceed during the process of a multi-stage crystal annealing in reducing atmosphere and in vacuum.

Results of investigations of Te doped GaAs, semiconductor nonlinear absorber, used for passive Q-switching of Nd:YAG laser resonators have been presented. The transmission changes dependence of the examined absorber on power density of the passing diagnostic radiation have been determined. There were estimated the following parameters: non-active losses, absorption cross-section, saturation energy, concentration of active centers, relaxation time, and energy losses caused by absorber bleaching. Generation characteristics of diode pumped YAG:Nd³⁺ laser with GaAs:Te modulator have been investigated. Generation of a train of pulses with duration of 6.5 ns, frequency of 6.7 kHz and energy 9 (mu) J has been obtained. Q-switched pulses showed intensity and timing jitter depending on the positions of intracavity elements.

Absorption, luminescence, ESR and ESA spectra and TL glow curves of YAG:Ce crystals codoped with Mg²⁺ ions and subjected to various treatments have been measured. The variations induced by irradiations in gamma and proton beams, and by thermal annealings under oxidation and reduction conditions point to large variations of the cerium ion valency. The ESA spectra of Mg-free and Mg-codoped crystals are clearly different with the peak value in the YAG:Ce, Mg sample higher and shifted towards the shorter wavelengths. Although the TL glow curves reveal the existence of the same major traps in both materials, their role in the overall deexcitation process is strongly modified upon Mg-codoping.

Electron Spin Resonance and optical absorption spectra of trivalent vanadium in Y₃Al₅O₁₂ crystals before and after (gamma) -irradiation and thermal annealing treatments are reported. The observed spectra are interpreted as arising from octahedrally coordinated V³⁺(3d²) ions. We obtained Lande factor 2g_x equals 2.237, and hyperfine structure constant A_(parallel) equals 330 X 10^-4 cm^-1 for T equals 4 K. It is possible to obtain tetrahedrally coordinated V³⁺ ions using annealing of YAG:V crystal in reducing atmosphere.

Epitaxial films with thickness of 10 - 250 micrometers of yttrium aluminum garnet (YAG) doped with Cr were grown by liquid phase epitaxy technique on YAG:Nd substrates. Co-doping with Mg²⁺ is used to force the Cr⁴⁺ valent state formation. Dependence of absorption spectra of obtained films on melt-solution composition, growth conditions and thermal treatment in reducing and oxidizing atmospheres is studied. A very intensive absorption band in UV region with maximum at 275 nm was found both in co-doped and YAG:Mg²⁺ epifilms caused probably by oxygen vacancies compensating the excess charge of Mg²⁺. Its intensity correlates with Cr⁴⁺ content in the film in that way: it decreases with Cr⁴⁺ entering in the film. The absorption being characteristic for YAG:Cr⁴⁺ crystals is found in co-doped films grown at higher temperatures (1000 - 1100 degree(s)C). The processes occurring during annealing are discussed.

Stable color centers influence on formation of the transient color centers in YAlO₃ and YAlO₃:Nd crystals grown in different atmospheres is studied. The mechanisms of transient optical property changes are discussed.

Emissions from charge transfer states of rare gas halide RgX molecules (XeF, KrF), alkali halide ions AX (CsF, CsCl, RbF), from vibrational states of CO and NO, and also from CO₂ molecules doped into rare gas and N₂ solids combine the known properties of gas phase lasers transitions with high densities of excited states attainable in the condensed phase. Cryogenic solids prepared by direct condensation of gas mixtures are grown routinely and allow for solid state laser experiments and also observation of strong luminescence bands in the VUV (B-X excimer transition of RbF at 136 nm), UV (B-X transition of CsF and CsCl at 196 and 210 nm; CsF(C-A) at 211 nm; XeF(D-X) at 269; 286 and 301 nm in Ne, Ar and Kr hosts, respectively), visible (XeF(B-X) and (C-A) at 411;541 nm) and infrared wavelength region (4.96; 5.4 and 16 micrometers bands of CO, NO and CO₂).