Papers by Keyword: Diffuse Phase Transition

Abstract: The microstructure and dielectric properties of ferroelectric solutions which is formulated with (1-x)[0.9Pb(Mg_1/3Nb_2/3)O₃-0.1PbTiO₃]-x mol% SrTiO₃ (x=0, 1, 3 and 5) have been investigated. The ceramics was fabricated by a modified columbite route sintered at 1200 °C. The effects of dopants on microstructure, maximum dielectric constant (ε_m) and diffuseness of the phase transition, etc. have been studied. It is found that the maximum permittivity (ε_m) increases to 24968 for the ST-doped (1 mol %) sample, subsequently decreases with ST addition and its corresponding phase-transition-temperature (T_m) shifts to the lower temperature. The variation of ε_m is caused by the decrease of polar nano-region size, increase of the fluctuation of the component and the increase of the effective spontaneous polarization. The enhancement of relaxor behavior in the PMN-PT sample is explained by the decrease of FE/AFE coupling.

Abstract: Pure and Hf-doped BaZr_0.2Ti_0.8O₃ (short for BZT) ceramics are prepared by a conventional solid state reaction method. The crystal structure and dielectric properties of Hf-doped BZT ceramics have been investigated. The results indicate that Hf4+ ions have entered the unit cell maintaining the perovskite structure of solid solution and the pure and Hf-doped BZT ceramics are cubic phase. Addition of hafnium leads to the fall of the phase transition temperature and can decrease the dielectric loss of BZT ceramics at room temperature. When Hf content is more than 0.5 wt.%, the diffuseness of the phase transition enhances with the increasing of Hf content and when Hf content is 3 wt.%, the diffuseness of Hf-doped BZT ceramics is more than that of the pure BZT ceramics.

Abstract: Ceramic solid solutions of (1-x)SrTiO3-(x)BiScO3 system with x=0, 0.05, 0.1, 0.2, 0.3, 0.4 and 0.5 have been for the first time synthesized via solid-state processing techniques. Both of end compounds in this system are not ferroelectric materials. X-ray diffraction analysis revealed that at room temperature the samples under study at x=0.2, 0.3, 0.4 and 0.5 consist of mixture of center-symmetric cubic Pm3m phase and polar tetragonal P4mm phase. Anomalous behaviour of dielectric permittivity and dielectric losses for these samples is found to be specific one for ferroelectrics with diffuse phase transitions. Furthermore, examination of the polarization hysteresis behavior revealed weakly nonlinear hysteresis loops in the ferroelectric phase.

Abstract: Dielectric properties and structural morphology of the Sc2O3 free and reduced lead content piezoelectric ceramic system, (1-x)Bi(Mg1/2Zr1/2)O3-xPbTiO3 (BMZ-xPT), were investigated in this study. The average grain size of the fresh fractured surfaces was of the order of ≤1 μm to ∼3 μm. The dielectric constant, loss tangent, Curie temperature, remnant polarization, coercive field, piezoelectric coefficient, and the planer coupling constant of ceramics in the vicinity of the morphotropic phase boundary (MPB) (x∼0.55) were, ∼1450, 0.0952, ∼553 K, 29 (μC/cm2) , 23 (kV/cm), ∼185 pC/N, and ∼30%, respectively. It was observed that with decreasing PbTiO3 contents the phase transition anomaly became broadened. The position of the dielectric constant maximum (ε′max) did not show any significant variation with probe frequency, exhibiting character of diffuse phase transition like many other disordered perovskites.