Preparation And Electric Properties Of Lead-Free (Na_0.5K_0.5)NbO₃ Piezoelectric Ceramics

Lead-free piezoelectric ceramics is a kind of "green" materials which does no harm to environment. It mainly includes: Lead-free piezoelectric ceramics based on BaTiO3, niobate piezoelectric ceramics. Lead-based PZT (Pb(Zr,Ti)O3) piezoelectric ceramic material has been taken a dominant position of the research and application in the piezoelectric ceramic area. Lead is highly toxic, however, as the requirements of human beings for the improvement of living environment quality, Lead-free materials as alkaline niobate piezoelectric materials in the area of research has attracted much attention. The electrical properties of doped and textured (Na0.5K0.5)NbO3(NKN) ceramics are comparable to the traditional PZT piezoelectric ceramics. So technique of preparing high properties lead-free piezoelectric ceramics becomes an important research topic.In this paper, (Na0.5K0.5)NbO3 1ead-free piezoelectric ceramics was prepared by the method of molten salt synthesis, the most appropriate processing parameters was conformed: the ratio of molten salt content and reactive materials was 1:1 and synthesizing temperature was 850℃for 4h. XRD analysis and SEM analysis showed: the NKN powder obtained from molten salt synthesis was not seriously conglobated, when the mass ratio between salt and the reactive materials was 1:1, the microstructure was spherical particles, and the particle size was 100-150nm; when the mass ratio between salt and the reactive materials was 2:1, the microstructure was cubic particles, and the particle size was 1μm approximately. Synthesizing temperature had a great impact on the phase structure of product; under a certain temperature, holding time did not greatly affect the purity of product. The growth process of NKN powder from molten salt synthesis method was controlled by the diffusion mechanism at low salt content, and controlled by interface growth mechanism at high salt content .The effect of CuO and CeO2 substituting content on the piezoelectric and dielectric properties of (Na0.5K0.5)NbO3 lead-free piezoelectric ceramics was also studied and discussed, respectively. Its result provided reference for the further research of doped (Na0.5K0.5)NbO3. The results showed that when CuO substituting content was 1.0mol% and sintering temperature was 1080℃, better comprehensive properties can be obtained; when CeO2 substituting content was 0.1mol% and sintering temperature was 1080℃, better comprehensive properties can be obtained.