Zinc doped titanium oxide (Ti<sub>1-x</sub>Zn<sub>x</sub>O<sub>2</sub>, x=0.05) abbreviated as Ti<sub>0.95</sub> Zn<sub>0.05</sub>O<sub>2</sub> (TZO) ceramic was synthesized by semiwet route using aqueous solution of zinc acetate dihydrate and solid titanium dioxide as starting materials. The single phase formation of the TZO ceramic sintered at 900 °C for 8 h was confirmed by powder X-ray diffraction (XRD) analysis. The lattice parameters obtained by Retvield refinement were found to be a=b= 4.609 Å, c= 2.967Å and α=β= γ= 90 ° with space group P 42/m n m confirmed the rhombic structure of TZO ceramic. The average particle size of the TZO ceramic observed by TEM analysis was found to be 84 nm. The surface morphologies and roughness parameters of TZO ceramic were observed by atomic force microscopy (AFM) analysis. The value of dielectric constant (ε′) and tangent loss (tan δ) of the TZO ceramic were found to be 230 and 0.2, respectively at 100 Hz and 498 K.
There are several mechanisms which have been proposed for the existence of colossal dielectric constant in the class of perovskite calcium copper titanate (CaCu<sub>3</sub>Ti<sub>4</sub>O<sub>12</sub> or CCTO) materials. Researches indicate that existence of twinning parallel to (100) (001) and (010) planes causes planar defects and causes changes in local electronic structure. This change can cause insulating barriers locally which contribute to the large dielectric values irrespective of processing. The combination of insulating barriers, defects and displacements caused by twinning have been attributed to the generation of large dielectric constant in CCTO. To examine some of these arguments some researchers replaced Ca with other elements and evaluated this concept. In this study we present the synthesis and characterization of Ga<sub>2/3</sub>Cu<sub>3</sub>Ti<sub>4</sub>O<sub>12-x</sub>N<sub>x</sub> (GCTON) material. This provides both distortion due to atomic size difference and defects due to insertion of nitrogen. The morphology of the compound was determined to show that processing has tremendous effect on the dielectric values. The resistivity of GCTON was several order higher than CCTO and dielectric constant was higher than 10,000.
Dielectric properties of high percentage Mg doped CaCu<sub>3</sub>Ti<sub>4</sub>O<sub>12</sub>, CaCu<sub>3-x</sub>Mg<sub>x</sub>Ti<sub>4</sub>O<sub>12</sub> (x=0.20 and 0.50) ceramics carried out. They were synthesized by the semi-wet route using a solution based citrate–nitrate method along with inexpensive solid TiO<sub>2</sub> powder. X-ray diffraction analysis reveals that the ceramics form single phase when sintered at 950 °C for 12h. SEM analyses show the smooth surfaces of grains with a spherical appearance. The grains of CCMTO2 and CCMTO5 ceramics were found to be in the size range of 1-5 μm and 1-3 μm, respectively. Dielectric studies show that the CCMTO2 ceramic has higher value of dielectric constant and lower dielectric loss in comparison to that of CCMTO5.