The 4th International Conference on Matter and Radiation at Extremes (ICMRE 2019)

551 / 2019-03-20 14:47:12

Predicted Polymorph Variation of Manganese Tellurate at High Pressure

Exotic perovskite A2BB’O6; Manganese tellurates; Structure prediction; High-pressure synthesis

Plenary track > High Pressure Physics and Materials Science

Exotic perovskite-related ABO3 and A2BB’O6 with small A-site cation allows the incorporation of transition metal cations at both the A and B/B’ sites, and thus additional magnetic functionality with possible robust magneto-electric properties is highly desired. Giving the small perovskite-related tolerance factor (t), the synthesis of these materials usually requires high-pressure over competition with other polymorphs, such as bixbyite, corundum derivatives, or LiSbO3-based structure. Therefore, prediction of the polymorph for atomic-scale structure engineering is very essential to facilitate the synthesis of desired phases. Here we briefly show the calculations and the corroborated experimental work on manganese tellurate.
The ambient-pressure synthesized manganese tellurate adopts a rhombohedral symmetry (R-3). Pressure-dependent prediction in line with the Murnaghan equation of state for solids (MESS) proposed the distorted double perovskite phase (P21/n) above 5 GPa, and the lack of desired polar corundum phase (R3) over intermediate pressure range, which was in good agreement with the subsequent high-pressure synthesis results. The polymorph variation is accompanied by dramatic physical properties evolution, and demonstrates magnetoelectric coupling temperature increasing in the high-pressure made perovskite phase. These findings for the first time show pressure induced reversible phase transition between Mg3TeO6 type R-3 phase and distorted GdFeO3-type P21/n perovskite structure.