Characterization of oxides obtained by heating a mixture of peroxoniobic acid and peroxotitanic acid

Abstract

Nb-doped TiO₂ particles were prepared by heating a mixture of peroxotitanic acid and peroxoniobic acid in air. When the heating temperature was more than 1173 K, the dominant phase obtained was rutile TiO₂, along with a small amount of TiNb₂O₇. The relationship between the lattice parameters of the obtained rutile TiO₂ depended on the molar fraction of Nb/(Ti + Nb). In the case where peroxo compounds were used as a precursor, a change in the lattice parameters of the rutile TiO₂ was observed within the lower X_Nb range, as compared to the alkoxide method. The results indicate that a homogeneous dispersion of doped Nb⁵⁺ ions in the obtained rutile TiO₂ lattice was achieved by using peroxo compounds. Furthermore, the oxide particles obtained by using peroxo compounds had a lower activation energy of the carrier electrons (E_a) and oxygen vacancies, even though the heating procedure was carried out in air. The UV-vis absorption spectra and Raman spectra of the obtained oxide particles indicated that the dominant reaction of the decomposition of O₂²⁻ ions in the TiO₂ lattice was O₂²⁻ → O₂ + 2e⁻ as a reducing agent.