Issue 33, 2022

Phase transitions and optical properties of the trigonal perovskite (CH3NH3)2TeCl6

Abstract

Vacancy-ordered double perovskites A2BX6 are attracting attention due to the isolated octahedra making them an ideal playground for studying perovskite structure-property relationships. MA2TeCl6 single crystals have been successfully grown from solution. X-ray structure experiments as a function of temperature have demonstrated two structural phase transitions: from cubic Fm[3 with combining macron]m (high temperature, phase I) to trigonal P[3 with combining macron]m1 (intermediate temperature, phase II) at 460 K and then to trigonal P[3 with combining macron]1c (low temperature, phase III) at 200 K. Intriguingly, we observe a negative thermal expansion for the c-axis in phase II believed to caused by dynamic tilting of the C–N bond in the MA+ ion. We have modified and extended the calculation of the Brown radii ratio in the perovskites to include hybrid A2BX6 compounds by selecting the shortest A–X distance for the ratio equation. We find that for ratios between 0.89 and 1.17, typically the Fm[3 with combining macron]m cubic structure is observed, while for ratios above 1.17, mostly distorted structures are found.

Graphical abstract: Phase transitions and optical properties of the trigonal perovskite (CH3NH3)2TeCl6

Supplementary files

Article information

Article type
Paper
Submitted
07 Jun 2022
Accepted
18 Jul 2022
First published
18 Jul 2022
This article is Open Access
Creative Commons BY license

J. Mater. Chem. C, 2022,10, 11938-11945

Phase transitions and optical properties of the trigonal perovskite (CH3NH3)2TeCl6

Y. Liu, J. K. Cockcroft, Z. Chen, M. A. Hayward, P. F. Henry, R. S. Perry and R. G. Palgrave, J. Mater. Chem. C, 2022, 10, 11938 DOI: 10.1039/D2TC02372E

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