Dielectric properties of normal, reduced, and specially reduced rutile (TiO2) single crystals at room temperature

Abstract

The variation of the dielectric constant (ε′) and the dielectric loss (ε″) have been studied as a function of frequency (10² to 10¹⁰ c.p.s.) for normal (as grown), reduced (heated in vacuum), and specially reduced (heated in vacuum in presence of an asymmetric d.c. field) rutile single crystals parallel to c-axis at room temperature. Dispersions in ε′ have been observed in the frequency ranges 10² to 10³ and 10⁷ to 10⁹ c.p.s. for all the samples with absorption peaks in ε″ at 2 × 10² and 6 × 10⁷ c.p.s. Also an extra absorption peak in ε″ has been found at 2 × 10⁴ c.p.s. for the specially reduced sample. The absorption peak at 2 × 10² c.p.s. has been observed by many workers and is typical for interfacial polarization. The peak at 6 × 10⁷ c.p.s. appears to be due to a dipole rotation process with a single relaxation time and is identified as due to relaxation of dipoles formed between Ti³⁺ and a neighboring oxygen vacancy. The possible mechanism of relaxation for the 2 × 10⁴ c.p.s. absorption peak is also discussed.