Preparation And Properties Of PNN-PZN-PZT Multilayer Free-standing Piezoelectric Thick Film

As a new type of piezoelectric material,piezoelectric thick film has the advantages of high driving force,wide working frequency and thin film material,low working voltage and good integration.The piezoelectric properties of single-layer thick films are often low,but higher piezoelectric properties can be obtained by multi-layer thick films.In this experiment,PNN-PZN-PZT piezoelectric material was used and the tape-casting thick films were prepared by tape casting method,and the screen-printed inner electrodes were fabricated into multi-layer parallel structures.After sintering,the multi-layer free-standing piezoelectric thick films were obtained.Further experiments were carried out to improve the deformation of the thick films.In this paper,a series of factors affecting the properties of thick films,such as tape casting,glue discharge,low temperature sintering,high temperature sintering,external doping,polarization process and multi-layer structure,were investigated.When using Ag electrodes,thick films sintered at 900?for two hours,then polarized at 120 C and 2.2-2.8 kv/m m for 15 minutes,the optimum piezoelectric properties of nine thick films can be obtained as follows:d₃₃=1880 pC/N,tan?=2.3%,?^T₃₃/?₀=1067,g₃₃=199.00mV.m/N,Pr=82.77 uC/cm²,and EDX element analysis of cross section shows that There was no diffusion and penetration at the sintering temperature.However,the lower sintering temperature will cause the porosity of thick film.Sintering Ag-Pa electrodes at high temperatures above 1000 C can effectively reduce the porosity of thick films and improve piezoelectric properties,but it will cause large deformation of thick films.The addition of Cu and Mn can play a role in reducing the sintering temperature when the amount of 0.25%dopant is added.The piezoelectric coefficient,residual polarization strength,displacement and overall strength of the thick film can be greatly improved by the multi-layer structure.The piezoelectric coefficient of the 9-layer thick film can reach 7 times of that of the block material,and the displacement of the same voltage can also reach 9 times of that of the bulk ceramics.In order to solve the problem of deformation in thick film sintering,two methods,sacrificial layer method and metal-ceramic electrode method,were proposed.Improving sacrificial layer method can completely eliminate the deformation of thick films,but it will restrict the shrinkage of thick films,thus affecting their porosity and electrical properties;while metal-ceramic electrode method can effectively reduce the number of deformation even though it can not completely eliminate the deformation without affecting the properties of thick films.