Structural Basis for the Anomalously Low Spontaneous Polarisation Values of the Polar Phase of Sr1 xCaxTiO3 (x=0.02, 0.04): Evidence for a Ferrielectric Ordering

摘要: Full pattern Le-Bail refinement using x-ray powder diffraction profiles of Sr1-xCaxTiO3 for x=0.02, 0.04 in the temperature range 12 to 300 K reveals anomalies unit cell parameters at 170, 225 due an antiferrodistortive (cubic tetragonal I4/mcm) phase transition and ~32, ~34 a polar (tetragonal I4/mcm orthorhombic Ic2m), respectively. The lower temperatures obtained by us are excellent agreement with those reported on basis dielectric studies Bednorz Muller, [10] who attributed these ferroelectric transition. Rietveld analysis off-centre displacements both Sr2+/Ca2+ Ti4+ ions X-Y plane along pseudocubic directions, experimentally direction easy polarization but resulting dipole moments shown be ferrielectrically coupled neighbouring (001) planes [001] leading anomalously low values spontaneous 12K.