Study Of Doping Modification On Bismuth Layer-structured Lead-free Piezoelectric Ceramic Material

Due to their own characters, bismuth layer-structured ferroelectric ceramics can be used as stable and high-Q piezoelectric activities of the conventionally sintered ceramics are low, resulting from their crystal structure in which the rotation of spontaneous polarization is two dimensionally restricted. With the help of the orthogonal design experiment, the single factor variable experiments doped with La (OH)₃ and WO₃, the influence of various components on the dielectric properties, fine texture, sintering temperature ,ferroelectric properties piezoelectric properties of calcium bismuth titanate (CBT)-based ferroelectric caramics had been investiagated. The influencing mechanism of various components on the dielectric properties of CBT-based ferroelectric caramics was studied. These provide the basis for preparation of matericals based lead-free piezoelectric ceramics .Bismuth layer-structured piezoelectric ceramics with improved piezoelectric constant obviously were obtained by A-site(LiCe) substitution for Ca. By means of XRD,SEM and other test methods, the effects of the crystal structure, morphology of grains on properties were given. The possibilities of La atom substituting A-site of BLSF were investigated by EDS.The effect of component and sintering temperature on the dielectric and piezoelectric properties of CBT-based lead-free piezoelectric ceramics was discussed adopting the orthogonal design experiment and composition optimizing program, so determine optimum recipe. On the basis of optimum composition, the influence rules and mechanisms of synthesizing temperature,holding time,milling time and sintering manner on the properties of CBT-based ceramics were studied . The results show that the ceramics have the best properties prepared by solid reaction process through optimum technological parameter ,which is 850℃synthesizing 3h ,milling time 8h ,10% excess Bi₂O₃ and buried sintering with Al₂O₃.On the ground of the optimum composition and optimum technological parameter, the effects of La³⁺ doping on properties and fine texture of CBT-based ceramics were studied. The behavior of the lead-free piezoelectric ceramic with potential ability reached the level as fellows: sintering temperature is 1130℃, dielectric constant(ε) is 166.85, dielectric loss(tanδ) is 0.0063,piezoelectric constant(d₃₃) is 11pc/N,remanent polarization(2Pr) is 36.3μC/cm², coercive field (2Ec) is 236 KV/cm.The lead-free piezoelectric ceramic was modified by WO₃ and explored employing single factor experiment, which has the best properties sintering temperature is 1120-1140℃, dielectric constant(ε) is 183.15, dielectric loss(tanδ) is 0.0046, piezoelectric constant(d₃₃) is 14pc/N, remanent polarization(2Pr) is 26.7μC/cm², coercive field (2Ec) is 220 KV/cm.The lead-free piezoelectric ceramic was modified by (LiCe) substitution for Ca, whose properties is as following: dielectric constant(ε) is 176.52, dielectric loss(tanδ) is 0.00579, piezoelectric constant(d₃₃) is 13pc/N.