To better understand the functional behaviors of optical gas sensor materials at high-temperature (~1000 K), the density functional theory has been employed to study the temperature dependence of the energy gaps in the sensor materials, including TiO2 and SrTiO3, due to the electron-phonon interaction and thermal expansion. In this study, the electron-phonon interaction is simulated using both Allen-Heine-Cardona (AHC) theory and finite displacement method, while thermal expansion study is based on the quasiharmonic approximation. The obtained results indicate that the band gap of TiO2 is predicted to widen as temperature increases from 0 K to 300K, and to narrow as temperature goes beyond 300 K. The refractive index exhibits a descending trend as temperature increases at 650 nm and 800 nm, which are in good agreement with experimental measurements. The band gap of SrTiO3 narrows monotonically as the temperature increases. Such results supply fundamental understanding and insights to the gas sensor materials at high temperature.

First-principles study of the temperature dependence of energy gaps in high-temperature gas sensor materials

256th National Meeting (2018)

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