The polycrystalline BaGd<sub>2-x</sub>O<sub>4</sub>: Tb<sub>x</sub> (x = 0.00 - 0.10) phosphors have been prepared by conventional high temperature
solid state reaction method. All the prepared samples were characterized by powder XRD and EDS techniques. The
photoluminescence (PL) and thermally stimulated luminescence (TSL) studies of these materials were investigated. For
PL studies the samples were excited with 263 nm UV light. All the samples showed strong green emission at 543 nm
due to <sup>5</sup>D<sub>4</sub>→<sup>7</sup>F<sub>5</sub> transition of Tb<sup>3+</sup> ions. PL peak intensity was found to increase with increasing dopant concentration.
For TSL studies, these samples were γ-irradiated with different dose rates using <sup>60</sup>Co source. TSL of these phosphors
showed a sharp glow peak with peak maxima at 394 K. It is found that the incorporation of terbium activator in
BaGd<sub>2</sub>O<sub>4</sub> host lattice resulted in the increase of TSL intensity. The luminescence results of these materials shows that
these are promising candidates for new green emission phosphor.
In order to understand the luminescence mechanism and luminescence centers in LaOCl, LaOBr and LaOBr:Tm, Thermally stimulated luminescence(TSL) and photoluminescence(PL) studies have been made on unirradiated and irradiated samples at room temperature. LaOCl revealed three glow peaks having their maxima at 355,390 and 410k while in LaOBr a shoulder at 335K and two glow peaks at 365 and 420k are observed. Incorporation of Tm in LaOBr resulted in significant changes in intensity. In addition,the shoulder at 335K gets suppressed and the 365 and 420K glow peaks shifted towards high temperatures to 380 and 430K. The shoulders at 355, 335 K in LaOCl and LaOBr have been attributed to impurities while the glow peaks at 390 and 380 K might originated due to radiative electron - hole recombination due to detrapping from chlorine and bromine ion vacancies. The high temperature glow peak at 420 and 430k might belong to F<sup>+</sup> centers being formed due to charge transfer between oxygen ion vacancies and excited electrons. The reflectance and photoluminescence studies supported these attributions as they revealed different emissions which may be responsible for color centers as well as luminescence centers.
Optically stimulated luminescence (OSL) of gamma-irradiated undoped KMgF<SUB>3</SUB> showed emission bands at 464 and 534 nm. Incorporation of Gd resulted in new emission bands around 275 and 310 nm. In RbMgF<SUB>3</SUB> four emission bands at 302, 400, 465, 800 and shoulders at 525, and 770 nm are observed, respectively. The strong emission band of Gd at 311 nm is suppressed significantly in OSL process of RbMgF<SUB>3</SUB>. The presence of Gadolinium in CsMgF<SUB>3</SUB> suppressed the 300 nm band seen in CsMgF<SUB>3</SUB> and resulted in a strong emission around 312 nm. The OSL emission spectra of LiBaF<SUB>3</SUB> consists of three emission bands and a shoulder at 385, 470, 535, and 415 nm, respectively. Doping of Europium in LiBaF<SUB>3</SUB> suppressed the OSL emission of LiBaF<SUB>3</SUB> and resulted in the characteristic emission of Eu<SUP>2+</SUP> at 360 and 414 nm. The OSL spectra of these samples have been compared with their thermally stimulated luminescence (TSL) spectra and the results are discussed in terms of the formation of F and V<SUB>k</SUB>-centers. The disappearance of certain bands has been attributed to the energy transfer processes between the activator and host.