New high-pressure phase of HfTiO4 and ZrTiO4 ceramics

TL;DR

This study investigates the high-pressure behavior of HfTiO4 and ZrTiO4 ceramics, revealing anisotropic compressibility, phase transitions, and structural changes including increased Ti-O coordination and volume collapse.

Contribution

It reports the discovery of a new high-pressure monoclinic phase in HfTiO4 and ZrTiO4 ceramics with detailed structural and compressibility analysis.

Findings

Non-isotropic compressibility with b-axis most compressible

Onset of structural phase transition at specific pressures

High-pressure phase involves increased Ti-O coordination and volume collapse

Abstract

We studied the high-pressure effects on the crystalline structure of monoclinic HfTiO4 and ZrTiO4. We found that the compressibility of these ceramics is highly non-isotropic, being the b-axis the most compressible one. In addition, the a-axis is found to have a small and negative compressibility. At 2.7 GPa (10.7 GPa) we discovered the onset of an structural phase transition in HfTiO4 (ZrTiO4), coexisting the low- and high-pressure phases in a broad pressure range. The new high-pressure phase has a monoclinic structure which involves an increase in the Ti-O coordination and a collapse of the cell volume. The equation of state for the low-pressure phase is also determined.