Study On Preparation And Modification Of Potassium Sodium Niobate-based Piezoelectric Ceramics

The preparation technology of potassium sodium niobate-based piezoelectric ceramics was studied by the method of sol-gel, and prepared pure piezoelectric ceramics of(K_0.5Na_0.5)NbO3?abbreviated as KNN? and modifying elements bismuth?iron?abbreviated as BF? doped(K_0.5Na_0.5)_1-xNb_1-xO₃-xBF?abbreviated as KNN-xBF? piezoelectric ceramics. When the sintering temperature was 1100 ? and the holding time was 2h, piezoelectric constant d33 of KNN-0.008 BF ceramics was 136pC/N, and the structure was orthogonal perovskite, more compact, more uniform the grain size, and degree of crystallization was more perfect.Alkali metal elements sodium and potassium were easy volatile in the sintering process, resulting in stoichiometric shifted, which affected the structure and properties of ceramics. Adding excess alkali metal elements sodium and potassium, preparation(K_0.496Na_0.496)Nb_0.992O₃-0.008BF-xNa?abbreviated as KNN-BF-x Na? and(K_0.496Na_0.496)Nb_0.992O₃-0.008BF-yK?abbreviated as KNN-BF-yK? piezoelectric ceramics. When the alkali metal element sodium excess doping dosage was 3mol%, ceramic obtained comparatively excellent structure and properties, and piezoelectric constant d33, electromechanical coupling coefficient Kp, dielectric constant ?r, dielectric loss tan? reached 149pC/N, 0.41, 641, 0.06, respectively. at the same time, ceramic had the single orthorhombic perovskite structure, and crystallization was more perfect, more uniform, better compactness.Doping sintering additive CuO to improve the structure and properties of the ceramics based on the excessive adding amount of alkali metal element sodium was 3mol%, prepared(K_0.496Na_0.496)Nb_0.992O₃-0.008BF-0.03Na?abbreviated as KNN-BF-Na? piezoelectric ceramics with different sintering additive dosage. When the doping dosage was 1mol%, grains growth better, crystal particle uniform, better compactness, and the ceramic was single orthorhombic perovskite structure, and piezoelectric constant d33, electromechanical coupling coefficient Kp, dielectric constant ?r, dielectric loss tan? reached 128pC/N, 0.37, 625, 0.08, respectively, which has good electrical properties.Design the orthogonal experiment of three factors and three levels, the effect of sintering temperature, the doping dosage of lithium and copper oxide was observed. The(K_0.5Na_0.5)_0.992-xNb_0.992O₃-0.008BF?abbreviated as KNN-BF?piezoelectric ceramics with different alkali metal elements Li and sintering additives CuO were prepared, and the structure, density ? and piezoelectric properties d33 of ceramics were analyzed. Grain size of samples were relatively uniform, and the density were relatively good, which have single tetragonal perovskite structure or a perovskite structure orthogonal. Through orthogonal experiment analysis and verification, when sintering temperature was 1100?, doping dosage of lithium was 4mol% and doping dosage of copper oxide was 0.5mol%, ceramic materials with more excellent piezoelectric property, piezoelectric constant d33 reached 99pC/N, and density reached 4.13g/cm3.