New lead-free piezoceramics based on knn

Abstract

Introduction. This paper shows the description of the methods used to obtain doped lead-free KNN piezoceramics: (K0.5Na0.5)0.95La0.05(Nb0.9Ti0.05)O2.9 and (K0.44Na0.52Li0.04)0.97La0.01Nb0.9Ta0.103 piezoceramics, and their physical characterization. The objective was to achieve a reproducible obtaining method that will promote good physicochemical properties in the systems used and to use new dopants such as Ti, with a lower price in the market, and La, not studied yet in the literature consulted, to modify and control their physicochemical properties. Methods. A combined method of grain growth reaction is used, to obtain the precursor NaNbO3 and from this we make it react in solid state with the other reactants, thus simplifying existent methods, and the characterization: dielectric, phase transition, structural characterizations by X-ray diffraction and piezoforce microscopy (PFM). Results. The photo-luminescence piezoceramics doped with La and Ti show a good power emission of blue light. In both compositions presented, the doping with the La cation regulates the grain growth, modifies dielectric properties, and lowers transition temperatures. In the KNN compound doped with Li-La-Ta, the phase coexistence at room temperature and good dielectric properties and a certain anisotropy in the orientation of the domains are obtained. The experimental results carried out by PFM demonstrate excellent piezoelectric constants def = 166 pCN-1 compared to the best PZT ceramics. Conclusions: the results presented favor their potential use as ferroelectric light emitters, as well as lead-free transducers. Neither composition has been internationally accredited yet.