Phase coexistence and evolution in sol-gel derived BY-PT-PZ ceramics with significantly enhanced piezoelectricity and high temperature stability

In this study,high Curie Temperature(T_(c))perovskite ceramics of optimized composition 0.55(0.1BiYbO_(3)-0.9PbTiO_(3))-0.45PbZrO_(3) with unique double orthorhombic main phases were prepared by a modified solgel method.Compared to the usual solid-state prepared sample,the sol-gel derived sample has a 1.6 times higher d_(33) of 325 pC/N,a 2.4 times higher remnant polarization,and a much better high temperature stability with similar depolarization temperature(T_(d))and T_(c).Comprehensive analysis of the xerogel prepared over a wide calcination temperature(T_(cal))range of 300-1000℃ revealed that perovskite structure appeared at only 400℃ and it became the main phase above 500℃.Comparison of XRD refinement results showed that calcination and sintering induced subtle and continuous phase transition,namely,the 400-900℃ calcined powders with coexisted tetragonal(P4mm)and orthorhombic(Pbam)phase changed to a rather stable double orthorhombic(Pmmm and Pbam)main phase in all the differently sintered ceramics,as similar to the 1000
C calcined powders.The stable phase coexistence well explains the enhanced performance.The results also demonstrate that optimized sol-gel processing can provide high T_(c) ceramics with desirable multi-phase structure and significantly enhanced performance at a lower temperature.

Structure tailorable triple-phase and pure double-polar-phase flexible IF-WS_(2)@poly(vinylidene fluoride)nanocomposites with enhanced electrical and mechanical properties

A new low-cost high-permittivity flexible nanocomposite consisting of a polyvinylidene fluoride(PVDF)matrix and fullerene-like tungsten disulfide nanoparticle(IF-WS2 NP)filler was fabricated via a simple solution route.A comprehensive investigation by X-ray diffraction,attenuated total reflection-infrared spectroscopy,and differential scanning calorimetry(DSC)showed that 0.5e1 vol% of IF-WS_(2) induced a nonpolar α-phase to coexisting triple-phase transition in PVDF,whereas a slightly higher loading of 2 vol% induced pure double-polar β- and γ-phases.These results indicate that the structure and properties of the fabricated nanocomposite are easily tailorable.DSC during heating and cooling cycles and morphology observations further indicated that a polar phase was induced by the nucleation effect of the IF-WS2 NPs and electrostatic interactions.As a consequence of the multiphase coexistence and structure homogeneity,nanocomposites with approximately 0.5-1 vol% of IF-WS_(2) NPs showed enhanced dielectric and energy-storage performance as well as enhanced tensile strength and elongation.The new phase-tailorable nanocomposites with balanced properties are promising for applications as energystorage capacitors,piezoelectric sensors,and other flexible multifunctional components.The results of this study will serve to deepen the understanding of the polymer polymorph and provide directions on new routes for fabrication of smart materials.