Raman study of barium titanate with oxygen vacancies

Barium titanate (BaTiO3) crystal samples with different distribution of oxygen vacancies were prepared through different thermal treatment processes. The influences of oxygen vacancies on the Raman spectra and X-ray photoelectron spectroscopy (XPS) spectra of BaTiO3 single crystals were studied comparatively. Raman measurements of fast-cooled BaTiO3, which annealed in vacuum and then cooled in air showed many different spectroscopic results comparing with as-received BaTiO3 sample. Raman measurements of slow-cooled BaTiO3, which annealed in vacuum and then cooled in tube furnace exhibited few spectroscopic differences. XPS measurements of as-received BaTiO3 sample and fast-cooled BaTiO3 sample confirmed that this discrepancy resulted from the surface phase of oxygen vacancy in BaTiO3.