# Rare 3 × 3 Layering in High‐Pressure Pseudo‐Perovskite Sr4Te4O15

## TL;DR

A new strontium tellurate compound, Sr4Te4O15, was synthesized under high pressure and temperature, revealing unique structural and electronic properties.

## Contribution

The study reports the synthesis and characterization of a rare pseudo-perovskite with 3 × 3 corrugated oxotellurate layers.

## Key findings

- Sr4Te4O15 crystallizes in the orthorhombic space group Pnma with specific unit cell parameters.
- The compound exhibits direct and indirect bandgaps of 3.17 and 2.97 eV, respectively.
- Thermal analysis shows Sr4Te4O15 transforms to SrTeO4 at elevated temperatures.

## Abstract

A novel strontium tellurate, Sr4Te4O15, has been synthesized under high‐pressure/high‐temperature conditions using multianvil techniques (9 GPa, 700°C). This unique composition constitutes both Te4+ and Te6+ sites and crystallizes in the orthorhombic space group Pnma with unit cell parameters a = 1332.4(1), b =1236.4(1), and c = 748.02(9) pm. The crystal structure of Sr4Te4O15 consists of heavily corrugated oxotellurate sheets made up of corner‐sharing [TeO6]6− octahedra and [TeO4]4− bisphenoids separated by layers of Sr2+. Some of its structural features are comparable to those of 2D perovskites, and the deviation of the compound from this class is discussed in terms of both structure and composition. The stability of this compound was investigated through high‐temperature powder X‐ray diffraction and thermal analysis revealing its transformation to SrTeO4 at elevated temperatures. Comprehensive characterization, including UV‐Vis, IR, and Raman spectroscopy, as well as density functional theory calculations, was performed to investigate its electronic structure, vibrational properties, and electron localization of the Te4+ lone electron pairs. The direct and indirect bandgaps were determined to be 3.17 and 2.97 eV, respectively. The study provides insights into the structural and electronic properties of Sr4Te4O15, contributing to the understanding of rare corrugated 2D pseudo‐perovskite systems.

High‐pressure/high‐temperature synthesis, crystal structure determination, and characterization of Sr4Te4O15, a rare (110)‐oriented pseudo‐perovskite with 3 × 3 corrugated oxotellurate layers, are presented. Thermal stability was studied by temperature‐dependent X‐ray powder diffraction. UV‐Vis, IR, and Raman spectroscopy, as well as density functional theory calculations, were performed to investigate the electronic structure, vibrational properties, and electron localization of the TeIV lone electron pairs.© 2026 WILEY‐VCH GmbH