Electrical and pyroelectric properties of lanthanum based niobate

A lanthanum based new tungsten bronze (TB) ferroelectrics (K2Pb2La2W2Ti4Nb4O30) was synthesized by a mixed-oxide method at high temperature. Thermogravimetry analysis (TG) technique was used to decide the material preparation conditions. The formation of desired compound was confirmed by preliminary X-ray structural analysis. The SEM micrograph of the sintered sample exhibits uniform rod-like grain distribution without many voids. Detailed studies of the nature of variation of dielectric parameters with temperature and frequency shows dielectric anomaly at 310 °C. The temperature dependence of electrical parameters (impedance, modulus, conductivity, etc) of the material exhibits a strong correlation between its micro-structure (i.e., bulk, grain boundary, etc) and electrical properties. The dc conductivity follows the Arrhenius equation, and thus its variation with rise in temperature reveals the negative temperature coefficient of resistance (NTCR) behavior of the material. The material obeys Jonscher's universal power law which is evident from the frequency dependence of ac conductivity. The variation of current with temperature shows that the material has high pyroelectric co-efficient and figure of merit. Hence the material is useful for pyroelectric sensors.

Variation of pyroelectric coefficient with temperature of KLN.Figure optionsDownload as PowerPoint slideHighlights
► This is an original work on complex TB-structured compound prepared by high temperature solid state reaction technique.
► The material has relatively high dielectric constant, low loss, and good ferroelectric property.
► The grain and grain boundary effects are prominent in the impedance plots, which are further strengthened by the modulus plots.
► The impedance and modulus data match the theoretical formulae.
► The material has high pyroelectric coefficient and figure of merit, thus making it a useful material for pyroelectric sensors.