The Study On Preparation And Properties Of ZnOw /PZT Piezoelectric Composite Materials

This thesis aims to investigate the preparation of high-quality ZnO whiskers(ZnOw) by combustion synthesis, to explore solutions to the basic preparation of ZnOw/PZT piezoelectric composite while lower sintering temperature and ameliorate the intrinsic brittleness of ceramics in order to improve the mechanical properties of piezoelectric ceramics, and then, trace additives such as Sb₂O₃ powders and ZnO nano-powders mixed with different content of ZnOw were doping into PZT to further improve the electrical and mechanical property of piezoelectric ceramic composites, respectively. The main work are as follows:(1) ZnOw were prepared by combustion synthesis methode, the crystal structure, morphology and phrase composition of the products obtained under different conditions were analys using XRD, SEM and EDS, respectively. Effects of temperature, time keeped in furnace and dragging out time on the morphology and structure of the products were discussed, growth mechanism of ZnOw were studied preliminary.The results show that: the products appears more flaky in low temperature about 900℃while keeped in short time and appears polygonal whiskers in high temperature of 980℃, optimum conditions for preparing high-quality ZnOw is keeped at 960℃for 3min and dragging out in 30 seconds, products obtained under this conditions shows the typical structure of hexagonal wurtzite ZnO.(2) Effects of different sintering temperature on density and piezoelectric properties of PZT ceramics were analysis, XRD, SEM and EDS were used to analyse the crystal structure, morphology and phrase content of PZT sintered in different temperature for 2 hours, the optimum sintering temperature range is 1050-1150℃.(3) Different content of modified ZnOw were doping into PZT to fabricate a series of ZnOw/PZT piezoelectric ceramic composite by solid-phase sintering method, XRD, SEM and EDS were used to analyse the crystal structure, morphology and phrase content of composite, the effects of different sintering temperature and different ZnOw content on density, microstructure, morphology, composition, electrical and mechanical properties of ZnOw/PZT piezoelectric ceramics composite were investigated, strengthening and toughening mechanism of ZnOw/PZT were revealed through content - structure - property relationships. The results show that the optimum is 2%ZnOw/PZT sintered at 1100℃with the value of relative density, d₃₃, Q_m, K_p,ε₃₃^T /ε₀, KIC,σ_f andσ_c were 98.61%, 272 pC·N^-1, 624.474, 0.5773, 1429.65, 1.76 MPa.m^1/2, 95.42 MPa and 485.16 MPa, respectively.(4) Effects on electrical properties of the composite as different content of Sb₂O₃ powder doping into PZT was also investigated. The results show that: As the content of Sb₂O₃ powder increase, d₃₃ andε₃₃^T /ε₀would firstly increase and then decrease while Q_m and K_p decrease consistently, the optimum addition of Sb₂O₃ powder is 0.5%. And then, effects to electrical properties and density of the composite while 0.5%Sb₂O₃ powder doping into ZnOw/PZT as trace additive was furtherly investigated. The optimum is 0.5% Sb₂O₃/ 2% ZnOw / PZT sintered at 1100℃, with the value of d₃₃, Q_m, K_p,ε₃₃^T /ε₀ and density are 293.17 pC·N^-1, 502.283, 0.5308, 1470.797 and 7.39 g/cm³, respectively. The value of d₃₃ increase, Q_m and K_p decreased slightly while the density is reduced substantially compared to 2% ZnOw / PZT.(5) Effects on electrical properties of the composite as different content of ZnO nano-powder doping into PZT was investigated, too. As the content of ZnO nano-powder increase d₃₃ increase butε₃₃^T /ε₀, Q_m and K_p decrease consistently. The optimum addition of ZnO nano-powder is 0.5%, with d₃₃ increase substantially whileε₃₃^T /ε₀, Q_m and K_p decrease slightly compared to PZT. Effects to electrical properties of the composite while 0.5%ZnO nano-powder doping into ZnOw/PZT as trace additive was furtherly investigated. The optimum is 0.5% Sb₂O₃/ 2% ZnOw / PZT sintered at 1100℃, with the value of d₃₃, Q_m, K_p andε₃₃^T /ε₀are 265.33 pC·N^-1, 649.861, 0.5146, 1326.267 and 7.3 g/cm3, respectively. The value of d₃₃ andε₃₃^T /ε₀increase, Q_m and K_p decreased slightly while the density is reduced substantially compared to 0.5% ZnOw / PZT.In summary, this thesis investigate experimental fabrication conditions of high-quality ZnOw by combustion synthesis, effects of ZnOw as a reinforcement phrase doping into PZT to density, structure ,electrical and mechanical properties of ZnOw / PZT composite and aslo the improvement of Sb₂O₃, ZnO nano-powders as trace additives to electrical properties of ZnOw / PZT composite, this provides referencable ideas for the research on design and preparation of novel piezoelectric composites with high mechanical and electrical reliabilities.