Pyroelectric properties of KTiOAsO₄ single crystals in the 4.2-300 K temperature range

The temperature dependence of the pyroelectric coefficient, γ_s(T), of KTA (KTiOAsO₄) single crystals grown by the top-seeded solution method self-fluxes has been studied in the 4.2-300 K temperature range. A novel approach to the pyroelectric measurement has allowed to take into account both the superionic conductivity of the crystal and the resistivity drop associated with thermal release of charge carriers from traps related to trace impurities. The γ_s(T) behavior in the 4.2-200 K temperature range is found to be similar to those of the isomorphic crystals belonging to the KTP (KTiOPO₄) family of crystals. The experimental results show that at the temperature of 200 K the true value of the KTA pyroelectric coefficient equals -(3.5±0.3)×10^-5 C/m² K. Two anomalies in the temperature dependence of the KTA pyroelectric coefficient have been revealed above 200 K, and they are discussed in terms of the superionic conductivity and structural changes associated with the temperature increase and isomorphic ion substitutions.