Optimisation of electrical conductivity and dielectric properties of Sn4+-doped (Na0.5Bi0.5)TiO3 perovskite

Abstract

The structural, microstructural, dielectric, and conductivity properties of Tin modified Sodium Bismuth Titanate (Na0.5Bi0.5)(Ti1-xSnx)O3, where x (mol%) = 0%, 1%, 3% (labeled as NBT, NBTS1, and NBTS3, respectively) were experimentally investigated in this paper. In this regard, the solid-state reaction process was used to prepare polycrystalline materials, where sintering was performed at 1100 °C for 3 h under atmospheric air. As a result, X-ray diffraction confirms, as it seems, the presence of a rhombohedral phase (R3c) in all compositions at room temperature. The electrical properties of the compositions are also studied using complex impedance spectroscopy (CIS). Subsequently, at room-temperature, doping 1% of Sn4+ in the NBT perovskite reduces the dielectric loss from 4.4 × 10−2 to 3.43 × 10−2 at 1 MHz. Moreover, it is around 3.05 × 10−2 at 93.6 °C and 1 MHz for NBTS3. Sn4+ significantly doping improved electrical conductivity. Therefore, at 10 Hz and 450 °C, the electrical conductivity of NBTS3 (σac = 8.76 × 10−3 S.m−1) is 61.26 times that of pure NBT (σac = 1.43 × 10−4 S.m−1). Joncher's power law investigates the conduction mechanism's nature; (i) the decreasing variation of the exponent s1 with temperature suggests that the NBT compound is characterized by the CBH (Correlated Barrier Hopping) model. On the other hand, for NBTS1 and NBTS3 (ii), the increase in s1 and s2 parameters under temperature indicates that the NSPT (non-overlapping small polaron tunneling) model is the most dominant. In this work, all tested compounds exhibit a sort of ferroelectric relaxation behavior. Our results demonstrate that doped materials can be applied to solid oxide fuel cells.