ferroelectric piezoelectric materials

Alkali metal niobate system (chemical formula ANbO3) is a class of important piezoelectric ferroelectric materials, the most representative piezoelectric sensor working is most widely used for lithium niobate (LiNbO3)at the same time. Lithium niobate has hexagonal structure at room temperature, and its point-space group is R3c. At about 1200 ℃, ferroelectric-paraelectric phase transformation of piezo crystal sounder sensor is the highest Curie point in existing piezo ceramic materials. Lithium niobate piezoelectric ceramics have a relatively small dielectric constant and high piezoelectric characteristics. However, the lithium niobate piezoelectric ceramic is a single crystal unit system, sintering is quite difficult, the sintering temperature of mechanical transducer piezo is very narrow, the temperature is slightly higher abnormal grain growth occurs, so that the mechanical strength greatly is reduced; at the same time containing alkali metal ions, Alkali metal ions partially evaporate the sintering, PZT piezoelectric generatoris resulting in difficulty in obtaining a uniform solid solution. In this regard, through various means to improve the sintering properties of lithium niobate piezoelectric ceramics. The mechanical strength of sintered lithium niobate ceramics can be greatly enhanced by adding CdO. A dense lithium niobate piezoelectric sensor datasheet was prepared by the method with a dielectric constant of 35.In addition to lithium niobate ceramics, binary and multiple alkali metal niobate ceramics is also a hot research. LiNbO3-NaNbO3 ceramics were prepared by sol-gel method. It was found that with the increase of Na content, the Curie temperature piezoceramic disc vibration sensor decreased and the piezoelectric properties improved. Breakthrough was made in the research of polybasic alkali niobate system ceramics in 2004, and a new ternary system was reported. The system is rhombic phase at x≤0.05, tetragonal phase at x≥0.07, and co-homogeneous phase boundary where two phases coexist at 0.05 <x <0.07. When the composition is in the same type phase boundary, the piezoelectric coefficient d33 can reach the maximum 235 pC / N, the electromechanical coupling coefficient is 48% and the Curie temperature is about 470 ℃.