Preperation And Capability Research Of KNN-Based Lead-Free Piezoelectric Ceramics

Piezoelectric ceramics have been widely used in devices of ultrasonic motors,sensors and transducers.Lead based ceramics are dominant in the market of piezoelectric materials,such as lead zirconate titanate?Pb?Zr,Ti?O₃?PZT??.But the high concentration of toxic lead?⁶0 wt%?is harmful to human and environment during the preparation,using and even disposal process.In consideration of sustainable development,the related laws and regulations have been legislated.Therefore,finding new series of environmental friendly lead-free piezoelectric ceramics has drawn increasingly worldwide attention.Potassium-sodium niobate ceramics?K,Na?NbO₃?KNN?are promising candidates for application as their excellent piezoelectricity and high Curie temperature?T_c?.In this work,Li,Sb and Ca?Bi,Na?ZrO₃?CBNZ?were used as dopants to modified?K,Na?NbO₃?KNN?ceramics.Three series of ceramics as?1-x?(K_0.48,Na_0.52)NbO₃-xCa_0.5(Bi_0.5,Na_0.5)_0.5ZrO₃,0.95(K_0.48,Na_0.52)_0.95Li_0.05Sb_xNb_?1-x?O₃-0.05Ca_0.5(Bi_0.5,Na_0.5)_0.5ZrO₃ and0.97(K_0.48,Na_0.52)_?1-x?Li_0.05Sb_xNbO₃-0.03Ca_0.5(Bi_0.5,Na_0.5)_0.5ZrO₃ were prepared by conventional sintering methods and the phase structures,dielectricity,piezoelectricity and microstructures have been systemically analyzed.First part is about the influence of CBNZ to?1-x?(K_0.48,Na_0.52)NbO₃-xCa_0.5(Bi_0.5,Na_0.5)_0.5ZrO₃?KNN-xCBNZ,x=0.01-0.07,0.09?ceramics.It is showed that,with the doping of CBNZ contents,the ceramics transfer from orthorhombic phase?O phase?to rhombohedral phase?R phase?and get an O-R phase boundary when 0.03?x?0.05 at room temperature.Second part based on the previous part,by changing the Sb contents,the influence of Sb to 0.95(K_0.48,Na_0.52)_?1-x?Li_0.05Sb_xNbO₃-0.05Ca_0.5(Bi_0.5,Na_0.5)ZrO₃?KNLS_xN-CBNZ,x=0-0.07,0.10?ceramics have been studied.The R-T phase boundary has also been obtained and an optimum properties of d₃₃²52pC/N,T_c²53°C,?_r=2200,tan?=0.039 have been got at x=0.06.Third part is explores the variation of phase structures,piezoelectricity,dielectricity and density of 0.97(K_0.48,Na_0.52)_0.95Li_0.05Sb_xNb_?1-x?O₃-0.03Ca_0.5(Bi_0.5,Na_0.5)ZrO₃?KNLS_xN-CBNZ,x=0.01,0.03,0.05-0.08,0.10?ceramics by doping antimony?Sb?.The rhombohedral?R phase?and tetragonal phase?T phase?boundaries were obtained and when x=0.06,the ceramics have optimum properties,d₃₃²67pC/N,T_c²53°C,?=4.63 g/cm³,k_p=0.452,?_r=1836,tan?=0.033.the ceramics have potential for applications in piezo-buzzer and piezo-igniter.