Structural transformation and transport behavior of mixed valence compound Sn3O4 under high pressure

Abstract

The effects of pressure on the crystal structure, band gap, and transport behavior of mixed-valence compound Sn3O4 have been studied using diamond anvil cell coupling with X-ray diffraction, UV–vis absorption, electrochemical impedance spectroscopy and resistance measurements. The experimental results demonstrated that the transport mechanism transfers from ionic to polaronic conduction starting at 6.3 GPa via mixed conduction between 1.9 GPa and 3.8 GPa, and then to large polaronic conduction at 18.8 GPa. The resistance showed a downward, upward and downward again in compression up to the highest pressure of our measurements, with a sharp change at 12.5 GPa. The temperature-dependent resistance measurements indicated semiconductor characteristics up to ~50 GPa. A significant decrease in the band gap from 2.69 eV to 1.29 eV was noted when applying pressure of 0.3 GPa and 37.8 GPa, respectively, suggesting the promising application of the material in the field of photocatalysis. The combined results of synchrotron XRD and Raman spectra demonstrate that the evolution of the photoelectric properties is induced by the pressure-induced crystal structure developments in layered mixed-valence Sn3O4. Our results facilitate a better understanding of the transport behavior of Sn3O4 under high-pressure, and provide insights for the design of high-performance photoelectric devices.