Preparation of high entropy (Ba0.2Mg0.2Ca0.2Sr0.2Pb0.2)TiO3 perovskite oxide powders by a sol-hydrothermal method

In this paper, a new kind of high-entropy (Ba0.2Mg0.2Ca0.2Sr0.2Pb0.2)TiO3 oxide powder was synthesized successfully by a wet-chemical method. The effects of reaction temperature, time and pH value of hydrothermal reaction on phase and morphology of the powders were studied. The results showed that the high entropy oxide powders had perovskite structure. The morphology of the powder was significantly affected by reaction conditions. With the increase of temperature, the powder morphology changed from rod to simple cubic. Perovskite phase can be obtained only when the pH value reached above 12.5. When the reaction condition was 100–120 °C for 24 h, the rod-like powders with pure perovskite phase were obtained. However, a secondary phase Pb5O8 appeared in the powders as the temperature was higher than 120 °C. Interestingly, 2 × 2 × 2 Pocket Cube-like powders with tetragonal perovskite structure were obtained by pH value of 13 when the hydrothermal reaction was at 160 °C–180 °C for 24 h. After sintering at 1200 °C for 2 h, the ceramic was completely single phase with tetragonal perovskite structure. It was almost no pores and the relative density reached 95%.