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Abstract: Sr x Ba1−x Nb2O6 (with x=0.50, 0.45, 0.40 and 0.30) ceramics were synthesized by conventional solid-state method and sintered at 1350°C for 3h. The phase structure, microstructure, dielectric, ferroelectric and pyroelectric properties of obtained ceramics were systematically investigated. Pure tungsten bronze phase could be obtained in all ceramics. The dielectric characteristics showed that SBN ceramic was a relaxor with strong diffuse phase transition and weak frequency dispersion. As Sr molar fraction x increases from 0.30 to 0.50, the transition temperature T C decreased linearly while the diffusivity parameter γ declined from 1.88 to 1.68. The saturated polarization, remnant polarization and pyroelectric coefficient were also found to be enhanced in SBN ceramics with increasing Sr content. The pyroelectric coefficient of about 2×10−8 C/cm2K can be obtained for polarized SBN50 ceramics at room temperature. [Copyright &y& Elsevier]

Abstract: Ba0.6Sr0.4TiO3 (BST)/MgO columnar composites are fabricated via the spark plasma sintering (SPS) method. The microstructure, dielectric and tunable properties of columnar composites are investigated. The unmodified BST Curie temperatures with the increase of MgO addition indicate a sufficient suppression of ions interdiffusion between the two phases. The dielectric constant is decreased from 7000 to 3800 when MgO weight ratio is up to 15% while the tunability still stays at high level over 45%. The coefficient of the dielectric nonlinearity β shows a growing trend with increasing MgO content. The experimental results are in agreement with the theoretical prediction and confirm that if the composite is fabricated in columnar model, a reduction of dielectric constant without a deterioration of tunability could be achieved, which make them useful for potential tunable device applications in wireless communication system. [Copyright &y& Elsevier]

Abstract: The dielectric properties of unpoled and poled Pb0.88Ba0.06Sr0.06(Mg1/3Nb2/3)0.37Zr0.375Ti0.255O3 (modified PMN–PZT) ceramics were investigated. It was found that the dielectric constant increased while the loss tangent decreased after poling. A frequency independent abrupt transition in the dielectric constant and loss tangent responses was observed for the poled ceramics. This abnormal behavior was believed to be correlated with the macro–micro domain transition and the corresponding pyroelectric measurement exhibited a narrow peak at the normal-relaxor transition temperature T nr. Furthermore, the presence of double-loop-like hysteresis and two types of current peaks at a temperature slightly higher than T nr showed another strong evidence of this transition. [Copyright &y& Elsevier]

Abstract: Porous Pb (Zr0.95Ti0.05) O3/xMgO (PZT/MgO, x=0, 0.1, 0.2, 0.5 and 1.0wt%) ferroelectric ceramics were prepared with MgO nanoparticles as reinforcing phase. The effects of MgO nanoparticles on the phase, microstructure, electrical and mechanical properties of as-prepared ceramics were investigated. The results show that the grain size is reduced obviously when increasing the amount of MgO. Compared with pure porous PZT, T C of MgO-added PZT ceramics shifts to higher temperature. Moreover, dielectric, ferroelectric and piezoelectric properties show no much degradation. Further, PZT/MgO ceramics possess enhanced mechanical properties compared to pure porous PZT ceramics, the largest increment of the fracture toughness and hardness being 31.3% and 19.8%, respectively. The optimal electrical and mechanical properties are obtained with the addition of less than 0.5wt% MgO nanoparticles. [Copyright &y& Elsevier]