Site selectivity of Sm3+ ions in BaBi4-xSmxTi4O15 ceramics and its influence on electrical properties

Samarium (Sm) substitution in BaBi4-xSmxTi4O15 for (x=0.00-0.50) is investigated. Raman spectroscopy reveals preferential substitution of Sm3+ for Bi3+ at the A-site up to x=0.20 in the perovskite block, and shows improvement in electrical properties. Beyond x=0.20, partial incorporation of Sm3+ into the (Bi2O2)(2+) layers leads to cationic disorder and a decrease in octahedral distortion resulting in poor dielectric and ferroelectric properties. The un-deviated "rigid layer" mode at 54 cm(-1) up to x=0.20 confirms stability of Bi3+ in the (Bi2O2)(2+) layers over the Bi3+ in the perovskite layers. Reduced electrical conductivity, low dielectric losses and improved ferroelectric polarization are seen for an optimum Sm content of x = 0.20. (C) 2015 Elsevier B.V. All rights reserved.