Effects of disorder activated scattering and defect-induced phase on the ferroelectric properties of BaSnxTi1-xO3 (0≤x≤0.28) ceramics

Abstract

BaSnxTi1-xO3 solid solutions with varying Sn content (x = 0.0–0.28) have been characterized for their structural, dielectric and ferroelectric properties. Rietveld analysis of high resolution X-ray diffraction (HRXRD) data reveals the coexistence of (tetragonal+orthorhombic) phases for x = 0.05, and (rhombohedral+cubic) phases for x = 0.12, and a single phase for the remaining compositions. Raman spectroscopy at room temperature reveals composition induced structural changes, and exhibits disorder-activated scattering at ∼110 cm−1 due to coexisting SnO6 and TiO6 octahedra in BaSnxTi1-xO3 compositions with Sn content x ≥ 0.1. Presence of SnO6 is confirmed both by Raman and infrared (IR) absorption spectroscopy. Incipient growth of a defect-induced semiconducting phase (BaSnO3) builds-up with increasing Sn content (x ≥ 0.05), but remains undetected by X-ray diffraction. It is prominently revealed by the high frequency Raman mode at ∼752 cm−1, which upon de-convolution shows the involvement of two overlapped modes. A decreasing intensity ratio of the two modes with increasing Sn content (x = 0.05–0.15) correlates with the observed decrease in remnant polarization, and a complete overlapping of the modes at a higher level of Sn content (x = 0.27) signifies the onset of relaxor behavior in the dielectric characteristics.