Preparation And Properties Of K_0.5Na_0.5NbO₃-xSiO₂Lead-free Piezoelectric Ceramics

Material is the basis of human life and production. The development of materialpromotes the development of human material civilization and progress of society.Considering the development of world technology, historical technology innovationusually started with material innovation. In the1970s, material, enenrgy andinformation were classified as the basis of modern technology. And in the1980s,new technology revolution which was marked by new material, biologicaltechnology and informational technology swept all over the world. In China, newmaterial study was classified as one of the seven improtant fields by Program863and later was classified as Improtant Program by Program973. Ceramic material asa tratidtional material underwent progressive development in this high and newtechnology revolution. Nowadays, people in and out of China are very active in thisresearch. Ceramic material has become an indispensable material in natinoaldevelopment.In many materials, KNN with wonderful ferroelectric, piezoelectric andpyroelectricity quality draws more attention. In this thesis I prepared potassiumsodium niobate ceramics which is doped with silica, and started a series of study.I first burned ceramics and prepared samples. Then I use x ray diffraction andelectron microscope techniques to study the composition of ceramics. Finally, westudied its performance through dielectric constants dependence with temperature,ferroelectric hysteresis loop and piezoelectricity parameters:(1) Using traditonal solid phase method we burned potassium sodium niobatepiezoelectric ceramics with different density of silica mixture. Samples are made bypolishing and electrode making. Then X ray diffraction is used to study the phaseand composition of sample ceramics. Scanning electron microscope is used to studyand analyze the micromechanism of the ceramics. Sintering temperature and samplequality are summarized and burning assistance of silica is discussed.(2) With dielectric test on ceramic samples, we obtained curves of ceramicsdielectric property which changes with temperature and curves of dielectric loss thatchanges with temperature. Phase-transition temperature of ceramic materials isobtained through analyzing its dielectric property. We studied the ferroelectrichysteresis loop of ceramics samples obtained through ferroelectric test, anddiscussed the influence of silica on the ferroelectric property of ceramics materials.(3) Through quasi-static method and resonance-antiresonance method, we obtainedceramics piezoelectric parameters, such as piezoelectric constants, electromechanical coupling factors and mechanical quality factors.The properties of the ceramics is better than non-doped ceramics. The sinteringtemperature is reduced effectively and density is improved by doped silica.Silica isa good assisted burning.