| Abstract: | (Sr 1 m x Ca x )Bi 2 Ta 2 O 9 ceramics with compositions x = 0, 0.2, 0.4, 0.6, 0.8 and 1.0 have been synthesized by conventional solid state route. Structural analysis of pellets were investigated using x-ray diffraction and micro-Raman spectroscopy. Substitution of Ca ion at Sr site was confirmed by decrease in lattice parameter calculated from x-ray diffraction data. Lowest Raman modes at 28.7 and 58 cm m 1 were found to increase in frequency with increasing Ca concentration and this was attributed to the lower mass and lower ionic radii of Ca. The temperature variation Raman studies showed a softening of the lowest phonon mode with increasing temperature. The increase in transition temperature with concentration of Ca in SBT compounds may be due to the decrease in tolerance factor. |
