Effects of La and O deficiencies on AC & DC electrical conduction in La2Ti2O7 ceramics

Frequency and temperature dependence of dielectric properties of La₂Ti₂O₇ ceramics in the respective ranges (10⁻¹ to 10⁶ Hz) and (123–473 K) are analysed. Grain, grain boundary and electrode polarisation effects are distinguished from impedance Cole-Cole analysis. Temperature dependence of grain capacitance reveals the polar nature of La₂Ti₂O₇. Charge carriers contributing to the observed changes in the temperature dependent dielectric constant εʹ, alternating current (AC) and direct current (DC) conductivity are identified. Temperature independent Jonscher's power law exponent (s ∼ 1) and the low polarizability strength, explain the stability of εʹ in the low temperature range (<283 K). Interaction of holes and electrons in accordance with Rezlescu's model is reflected as a dip in the temperature dependent DC conductivity, and a diffused hump in εʹ(T) in the low temperature range (123–250 K). Electrical conductivity in the high temperature range (250–473 K) is attributed to hopping mechanism.