Influence of Al doping on structural and dielectric properties of YFeO3 multiferroic system

Abstract

Structural evolution, dielectric and electrical polarization measurements as a function of temperature and frequency, for Y(Fe_1-xAl_x)O₃, 0.0 ≤ x ≤ 0.075, have been evaluated. Structural analysis showed that 7.5 % of Al doping in the YFeO₃ matrix, shrinking the cell volume by about 3 %. XPS studies revealed that oxidation states of cations are Fe³⁺, Fe²⁺, and Al³⁺, being Fe³⁺ the most predominant state. Dielectric constant and loss tangent measurements, as a function of temperature and frequencies, for YFeO₃ exhibited a step-like anomaly around 450 K. Al doping led to a reduction in both the anomaly and the weak electrical polarization. Furthermore, at the high doping level, the tan (δ) and electrical conductivity at room temperature and low frequencies, decreased by 95 %, and 99 %, respectively. The activation energy obtained from AC conductivity, using Arrhenius-type equation, varied from 0.9 to 1.1 eV in the high temperature regime and it is related with ionic conductivity.