Study Of Low-loss PZT Piezoelectric Ceramics

Recently, research works on high-power piezoelectric ceramics become an interesting topic due to their increasing application in piezoelectric motors, transformers and piezoelectric transducer. The preparation of high-power piezoelectric ceramics with high piezoelectric properties and low dielectric loss at high electrical field were studied in this paper. A kind of binary system piezoelectric ceramic with good properties was selected. The doping effect and preparation technology were researched. The high electrical field effect and dielectric loss mechanics were preliminarily discussed by means of measurement of materials properties at high electrical field.The study on doping modification of ceramics shows that: cerium oxide (CeO2) with proper content can decrease the relative dielectric constantεr and mechanical quality factor Qm a little. But the addition of CeO2 can settle the problem that the ceramic was hard to be polarized under high temperature and high electrical field. The piezoelectric properties of the materials are displayed sufficiently, the expression of which is the obvious increace of piezoelectric coefficient d 33 and electromechanical coupling coefficient Kp and apparent decrease of dielectric loss tgδ. The optimized properties are obtained when the doping content of CeO2 is 0.4 mol%.The effect of sintering technique, poling technique, cold isostatic compaction and oxidation treatment were researched about the material with 0.4 mol% CeO2. The experiment results show that 1230℃is the optimum sintering temperature when the ceramic has excellent comprehensive properties for application of high-power piezoelectric ceramics. The property parameters are listed below:εr=1022, tgδ=0.16%, d 33=227 pC/N, Kp =0.45 and Qm =998; The experiment results of poling technique show that reducing poling temperature in oder to increase electrical field is the effective method to improve poling effect; Compared with dry pressed ceramics, the ceramics of cold isostatic compaction have smaller crystal grain and higher density, but worse dielectric properties and piezoelectric properties; The properties of the materials become better after two hours oxidation treatment under 850℃.The measurement of dielectric properties at high electrical field shows that with the increace of electrical field, the rate of dielectric constant-temperature curve becomes smaller, that means temperature stability of dielectric constant becomes better; The dielectric loss increases when electrical field increases, and it changes from 0.16% to 0.38% as electrical field changes from 0 V/mm to 400 V/mm. Although dielectric loss becomes bigger, it is still a small value. So the material discussed in this paper is suitable for the application of high-power piezoelectric ceramics at high electrical field.