Lead-free(K_(0.4425)Na_(0.52)Li_(0.0375))(Nb_(0.8825)Sb_(0.07)Ta_(0.0475))O_(3)(KNLNST)piezoelectric ceramics are synthesized by the conventional solid-state reaction method.The sintering temperature and poling temperature dependence of ceramic properties are investigated.Previous studies have shown that variation of sintering temperature can cause phase transition,similar to the morphotropic phase boundary(MPB)behavior induced by composition changes in Pb(Zr,Ti)O_(3)(PZT).And the best piezoelectric performance can be obtained near the phase-transition sintering temperature.In this research,phase transition induced by sintering temperature cannot be detected and excellent piezoelectric properties can still be obtained.The sintering temperature of the largest piezoelectric coefficient of such composition is lower than that of the highest density,which is considered in composition segregation as a result of intensified volatilization of alkali metal oxides.Combined with the effect of poling temperature,the peak values of the piezoelectric properties are d_(33)=313 pC/N,k_(p)=47%,ε_(r)=1825,tanδd=0.024,T_(o-t)=88℃,and TC=274℃.
Large-scale synthesis of ZnO hexagonal pyramids was achieved by a simple thermal decomposition route of precursor at 240 oC in the presence of PEG400. The precursor was obtained by room-temperature solid-state grinding reaction between Zn（CH3COO）2-2H2O and Na2CO3. Crystal structure and morphology of the products were analyzed and characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM） and high-resolution transmission electron microscopy （HRTEM）. The results of further experiments show that PEG400 has an important role in the formation of ZnO hexagonal pyramids. Difference between the single and double hexagonal pyramid structure may come from the special thermal decomposition reaction. The photoluminescence （PL） spectra of ZnO hexagonal pyramids exhibit strong near-band-edge emission at about 386 nm and weak green emission at about 550 nm. The Raman-active vibration at about 435 cm-1 suggests that the ZnO hexagonal pyramids have high crystallinity.
