Quest for lead free relaxors in YIn_1–xFe_xO₃(0.0 ≤x≤ 1.0) system: role of synthesis and structure

Abstract

The B-site tailored YIn_1–xFe_xO₃ (0.0≤ x≤ 1.0) series was synthesized by glycine-aided gel-combustion technique and subjected to extensive structural and electrical investigations. The temperature had tremendous bearing on the phase evolution exhibited by the system. The entire system crystallized as C-type metastable polymorph in the as–synthesized form. Hexagonal polymorphs of Fe³⁺-rich compositions could be isolated by controlled heat treatment at 750 °C. Raman spectroscopic investigations showed that, while there is a general shrinkage of the lattice due to substitution of a smaller ion at In³⁺-site, there is an apparent dilation of the Y–O bond, and this anomaly reflects in the electrical behavior exhibited by the system. The single-phasic hexagonal nominal compositions, YIn_1–xFe_xO₃ (0.0 ≤ x ≤ 0.3), were also studied by impedance spectroscopy. The dielectric constant was found to drastically increase from 10 for YInO₃ to 1000 for YIn_0.7Fe_0.3O₃ at room temperature stressing the role of B-site tailoring on electrical behavior. More interestingly, careful substitution of Fe into YInO₃ could tune the electrical behavior from a dielectric to relaxor ferroelectric in the temperature range studied. The nominal composition YIn_0.7Fe_0.3O₃ showed a classical relaxor ferroelectric like behavior which is an important observation in context of the search for new lead free relaxor materials.