Doping and temperature-dependent optical properties of oxygen-reduced BaTiO3-d

TL;DR

This study investigates how doping and temperature influence the optical properties of oxygen-reduced BaTiO3-d, revealing phase transitions, metallic behavior, and midinfrared absorption changes linked to oxygen vacancies.

Contribution

It provides new insights into the temperature-dependent optical behavior and phase transitions of oxygen-reduced BaTiO3-d across different doping levels.

Findings

Structural phase transitions detected via infrared-active phonons.

Metallic ground state confirmed by Drude-like reflectance.

Midinfrared absorption band correlates with oxygen vacancy concentration.

Abstract

We report on optical properties of reduced BaTiO3-d at different doping levels including insulating and metallic samples. In all the samples, including metallic one, we observe structural phase transitions from the changes in the infrared-active phonon modes. Metallic ground state is confirmed by the Drude-type lowfrequency optical reflectance. Similar to SrTiO3-d we find that the midinfrared-absorption band in BaTiO3-d appears and grows with an increase in the oxygen-vacancy concentration. Upon decrease in temperature from 300 K, the midinfrared band shifts slightly to higher frequency and evolves into two bands: the existing band and a new and smaller band at lower frequency. The appearance of the new and smaller band seems to be correlated with the structural phase transitions