Preparation, structure and dielectric properties of tungsten bronze ferroelectrics in SrO-Eu₂O₃-TiO₂-Nb₂O₅ system

Abstract

Compounds Sr₄Eu₂Ti₄Nb₆O₃₀ and Sr₅EuTi₃Nb₇O₃₀ with filled tetragonal tungsten bronze structure were prepared, and the dielectric characteristics and ferroelectric transition were investigated. Both ceramics displayed weak frequency dependence in room temperature dielectric constant, which decreased from 125 to 118 for Sr₄Eu₂Ti₄Nb₆O₃₀, from 206 to 195 for Sr₅EuTi₃Nb₇O₃₀ in the frequency range of 10 kHz to 1 MHz. The present ceramics showed a diffuse ferroelectric phase transition. The frequency independent transition temperature (T _m) indicated the above compounds had no relaxor property. The diffuseness (γ) was 1.45 and 1.64 for Sr₄Eu₂Ti₄Nb₆O₃₀ and Sr₅EuTi₃Nb₇O₃₀ respectively. The weak ferroelectric of the present materials are indicated from the P-E hysteresis loops, and a small 2P _r of 0.596 μC/cm² and 0.068 μC/cm² were observed for Sr₄Eu₂Ti₄Nb₆O₃₀ and Sr₅EuTi₃Nb₇O₃₀ respectively.

Keywords

tungsten bronze / dielectric properties / X-ray diffraction / phase transition

References

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