Effect of Oxygen Content on Dielectric Properties of Float Zone Grown Titanium Dioxide (TiO2) Crystal

Dielectric studies have been carried out to see the effect of oxygen content on two different sets of rutile (TiO2) single crystals grown by float zone technique. One set is having pale yellow colour which is the correct characteristic colour of rutile crystals whereas another have dark blue colour which contains oxygen deficiency. The variation of dielectric constant ('), the dielectric loss (tan ) and the electric conductivity () at different temperature and frequency of the applied electric field was studied for both these crystals. There is significant change in the values of dielectric constant for blue sample as compared to yellow sample. The dielectric constant in most of the region for oxygen deficient crystal (blue colour) is large as compared to true stiochoimetric ratio (pale yellow) of the rutile crystal. Based on conductivity behaviour, it was found that the correlated barrier hopping (CBH) model is the most predominant hopping mechanism in the case of the yellow crystal, whereas in the case of the blue crystal, hopping may be due to overlap of large polarons.