The effect of non-equimolar doping on the preparation and electrical conductivity of Sr(Ti,Zr,Zn,Sn,Hf)O3-σ high entropy perovskite oxide

A series of high entropy oxides (HEOSs) with non-isomolar ratios of perovskite structures were prepared by ball milling a mixture of SrO, TiO2, ZrO2, ZnO, SnO2 and HfO2 followed by sintering using a high-temperature solid-phase method. Both XRD and TG-DSC results indicate that single-phase Sr(Ti0.2Zr0.2Zn0.2Sn0.2Hf0.2)O3-σ is formed at 1500 °C. According to the SEM-EDS pictures, the elements in the oxide are uniformly distributed with no significant segregation or accumulation. The TEM results show that the polycrystalline ceramic powders can be classified as orthogonal Pbnm perovskite structure. The electrical conductivity (σ) was measured by the EIS technique and the activation energy (Ea) of HEOSs is calculated. In the temperature range of 300–750 °C, Sr(Ti0.28Zr0.18Zn0.18 Sn0.18 Hf0.18)O3-σ exhibits the highest conductivity (2.41 × 10−3 S/cm) and the lowest activation energy (Ea = 0.57 eV) due to lattice distortion and oxygen vacancy concentration.