Solid state synthesis and structural refinement of polycrystalline La_xCa_(1-x)TiO_3 ceramic powder

摘要

Perovskite structure based ceramic precursors have a characteristic property of substitution in the "A" site of the ABO_3 structure. This makes them a potential material for nuclear waste management in synthetic rock (SYNROC) technology. In order to simulate the mechanisim of rare earth fixation in perovskite, La_xCa_(1-x)TiO_3 (where x = 0.05) has been synthesized through ceramic route by taking calculated quantities of oxides of Ca, Ti and La as starting materials. Solid state synthesis has been carried out by repeated pelletizing and sintering the finely powdered oxide mixture in a muffle furnace at 1050 deg C. The ceramic phase has beer characterized by its powder diffraction pattern. Step analysis data has been used to determine the structure of solid solution of lanthanum substituted calcium titanate. The SEM and EDAX analyses also confirm that the CaTiO_3 can act as a host for lanthanum. X-ray data has been interpreted using CRYSFIRE and POWDER CELL softwares. The h, k, I values for different lattice planes have been generated from (he experimental data. The lanthanum substituted perovskite crystallizes In orthorhombic symmetry with space group P n m a (#62). Following unit cell parameters have been calculated: a = 5.410,b= 7.631, c= 5.382.The calculated and observed values of corresponding Intensities, 2 theta, and density show good agreement, GSAS based calculation for bond distances Ti-O, Ca-O, La-O and bond angles Ti-O-Ca, Ca-O-Ca, La-O-Ti have been reported.