High temperature dielectric investigation, optical and conduction properties of GdFe_(0.5)Cr_(0.5)O_3 perovskite

摘要

The present study reports the synthesis of GdFe_(0.5)Cr_(0.5)O_3 by a conventional solid-state reaction route and the investigation of its structural, morphological, and optical properties. Dielectric and electric behaviors as a function of both high temperature and frequency are also presented. GdFe_(0.5)Cr_(0.5)O_3 crystallizes in a Pbnm orthorhombic cell with an average grain size of 670 nm. The Mossbauer spectrum at room temperature shows the existence of Fe~(3+) in an octahedral symmetry with the presence of short-range order between the antiferromagnetic and the paramagnetic states. An optical study reveals a direct bandgap with an energy of about E_g = 1.87 eV. The dielectric relaxation is explained based on the Maxwell-Wagner polarization mechanism asserted to be arising in the interfaces of grains and grain boundaries. The charge carrier hopping is assumed to be along the (Fe, Cr)~(3+) -V_O~·-(Fe, Cr)~(2+) chain. A high temperature dielectric study is performed between 298 and 800 K, revealing successive transitions presumed to be associated with magnetic and electric ordering. The conduction mechanism is provided by the correlated barrier hopping model, while the ac-conductivity, at high temperatures, is dominated by oxygen vacancy motion.