Electrical properties of Nb-, Ga-, and Y-substituted nanocrystalline anatase TiO ₂ prepared by hydrothermal synthesis

Nanocrystalline anatase titanium dioxide powders were produced by a hydrothermal synthesis route in pure form and substituted with trivalent Ga ³⁺ and Y ³⁺ or pentavalent Nb ⁵⁺ with the intention of creating acceptor or donor states, respectively. The electrical conductivity of each powder was measured using the powder-solution-composite (PSC) method. The conductivity increased with the addition of Nb ⁵⁺ from 3 × 10 ^-3 S/cm to 10 × 10 ^-3 S/cm in as-prepared powders, and from 0.3 × 10 ^-3 S/cm to 0.9 × 10 ^-3 S/cm in heat-treated powders (520°C, 1 h). In contrast, substitution with Ga ³⁺ and Y ³⁺ had no measureable effect on the material's conductivity. The lack of change with the addition of Ga ³⁺ and Y ³⁺, and relatively small increase upon Nb ⁵⁺ addition is attributed to ionic compensation owing to the highly oxidizing nature of hydrothermal synthesis.