Dielectric and pyroelectric properties of niobium based complex tungsten bronze ferroelectrics

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This paper highlights the dielectric and pyroelectric properties of two new complex tungsten bonze ceramics (K2Pb2Eu2W2Ti4Nb4O30 and K2Pb2Nd2W2Ti4Nb4O30) which were prepared by a high temperature mixed oxide method. Room temperature X-ray structural analysis confirms the formation of single phase compounds. The SEM micrographs show uniform distribution of densely packed rod like grains. Variation of dielectric parameters with temperature (27–500 °C) and frequency (1–5 MHz) shows the phase transition at 315 and 299 °C for the above mentioned respective samples. The temperature dependence of hysteresis loops confirms the existence of ferroelectricity in the materials below transition temperature. The current variation with voltage at different temperatures shows the semiconducting behaviour of the materials. The nature of temperature dependent dc conductivity follows the Arrhenius equation, and reveals the negative temperature coefficient of resistance behaviour of the materials. The current (for a fixed voltage) variation with temperature shows that the materials have high pyroelectric co-efficient and figure of merit, thus making them useful for pyroelectric sensors.