Oscillatory variation in EMF developed due to additions of TiO₂ pretreated thermally and γ-irradiated to various doses in the concentration cell made up of Ag/Ag⁺

Abstract

Several powder samples of TiO₂ are pretreated thermally at 300, 480 and 540°C, subjected to γ-irradiation and after irradiation added in one of the compartment of the concentration cell made up of Ag/Ag⁺. The adsorbed oxygen species O ⁻_2ad , HO ⁻_2ad and O ⁻_ad on TiO₂ provide negatively charged sites and develop EMF in the cell. The radiation damage, measured in terms of equilibrium EMF, received at lower doses is partially recovered at higher doses. It is proposed that in heating at 480°C, ‘ad’ species react with Ti³⁺ ions in the surface and produce −O−O− peroxy linkages and block the negatively charged sites while in heating at 540°C Ti₄O₇ phase is produced on the surface which adsorbs O₂ and provide large number of negatively charged sites. During γ-irradiation peroxy linkages are broken and the Ti₄O₇ phase is destroyed. Observed oscillatory variation in equilibrium EMF is explained on the basis of several reactions mentioned above proceeding at different rates during radiolysis.