High-pressure bandgap engineering and amorphization in TiNb2O7 single crystals

Abstract

Titanium niobate (TiNb₂O₇) possesses excellent photocatalytic properties, dielectric properties, and lithium-insertion capacity. High-pressure (HP) treatment is a powerful tool for bandgap engineering aiming at widening its applications. Herein, we report the growth of TiNb₂O₇ single crystals by the optical floating zone (OFZ) method and the engineering of the TiNb₂O₇ bandgap via HP. To obtain the physical mechanism of the bandgap variation under HP, the detailed pressure-dependent properties and structure information have been characterized by using in situ Raman spectroscopy and angle dispersive synchrotron radiation X-ray diffraction (ADXRD). During compression, the TiNb₂O₇ crystals were amorphized and the amorphized phase was maintained under ambient conditions. The microstructures of the uncompressed crystalline and decompressed amorphized samples have also been investigated accordingly.