Problems with PZT piezoelectric ceramics powder(1)

Views: 3 Author: Site Editor Publish Time: 2018-10-14 Origin: Site

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PZT piezoelectric ceramics have been the focus of attention and research since the 1960s due to its high curie temperature, strong piezoelectricity, easy doping modification and good stability. In the field of piezoelectric ceramics. In terms of the preparation process of PZT piezoelectric ceramics, PZT powder synthesis and densification sintering have the greatest influence on the quality of PZT products. PZT powder has the advantages of fine particle size, large specific surface area and high reactivity. It can reduce sintering temperature, lead volatilization,which ensure accurate stoichiometry, and improve the performance of PZT products. Therefore, the preparation of ultrafine PZT powderhas become PZT piezoelectric ceramics.which is the focus of research.

In recent years, many new methods have been developed for the research on the preparation of ultra fine PZT piezo ceramic materials. The solid phase method includes microwave radiation method, mechanical chemical method, reaction sintering method, and the like in addition to the conventional solid phase method. The liquid phase method has the advantages of low synthesis temperature, simple equipment, easy operation, low cost, etc., which has been used for the preparation of PZT powder, such as sol-gel method, hydrothermal method, precipitation method and the like. However, there are still many shortcomings in the preparation and performance of PZT piezoelectric ceramics, including powder agglomeration, stoichiometry and easy aging of product properties.Powder agglomeration: which generally includes soft agglomeration and hard agglomeration. Soft agglomeration is due to the increasing and interaction of van der Waals force, electrostatic attraction and capillary force between particles as the particle size decreases; hard agglomeration is due to hydrogen bonding between chemically bonded OH groups [2OH H2O(g) + O2-] forms a bridge oxygen bond, and a bridge oxygen bond between the particles forms an interaction. Agglomeration problem The most important factor in the performance of ultra-fine Pzt Ceramic Powder is also greatly affecting the quality of PZT products. This is because the PZT material is a functional material. The basic material requirements for the synthetic powder are high purity, ultrafine, uniform particle distribution, good dispersibility, accurate stoichiometry, and uniform doping. In addition, the occurrence of agglomeration. PZT powder synthesis will lead to a decrease in bulk density and uneven morphology, and will introduce a large number of pores resulting in uneven microstructure, which seriously affects the piezoelectric and thermoelectric properties of low PZT products. Therefore, reducing or avoiding agglomeration in the synthesis of ultrafine PZT powder is a prerequisite for the preparation of high performance PZT piezoelectric ceramics.

The agglomeration in the preparation of ultrasonic polarized piezo transducers includes two forms of soft and hard agglomeration. The agglomeration mechanism is also different for different powder preparation methods. The traditional solid phase synthesis of PZT powder is characterized by repeated ball milling and high calcination temperature. Repeated ball milling not only introduces impurities, but also over-grinding leads to the formation of agglomeration. Especially the mechanochemical method developed in recent years mainly uses mechanical energy is completed; high calcination temperature may also cause powder agglomeration. The PZT powder is synthesized by the liquid phase method, and the solid phase particles in the liquid phase generally undergo nucleation, growth, coalescence, agglomeration and the like. Therefore, its agglomerated structure may be formed in: First, solid phase particles are formed in the liquid phase. Due to the action of Brown, the particles are close to each other. When the kinetic energy between the particles is larger than the barrier forming the agglomerates, the particles agglomerate under the action of brown movement; the second is in the process of solid-liquid separation. The elimination of the liquid phase causes the solid phase particles to come together close to each other due to the surface tension.In particular, the custome pzt piezoelectric disks powder is synthesized by using water as a solvent, and the trace amount of water which is remaining between the particles will bond the particles and the particles tightly by hydrogen bonding. In addition, the prepared PZT powder precursor is generally calcined at 500-700°C, which may also cause powder agglomeration, and may also cause to aggravate the formation of agglomerated structures due to local sintering. It can be seen that the preparation of PZT powder by coprecipitation method, coprecipitation, grain growth to precipitation, drying, and calcination of each segment may lead to particle growth and formation of agglomerates. According to the formation of agglomeration, reducing or avoiding particle growth and agglomeration in the preparation of ultrafine PZT powder can be considered from the following aspects: