Study On Microstructure And Fatigue Characteristics Of 1-3 Type PMN-PT Based Piezoelectric Composite

The fatigue effect and long-term load effect of building structure in service,as well as the erosion and aging of building materials,will lead to the reduction of material strength and accelerate the damage of the structure.Therefore,buildings need timely warning and real-time health monitoring.Structural monitoring and inspection and condition assessment strongly depend on the performance of sensors and transducers.Piezoelectric materials have become the most commonly used functional raw materials in structural health monitoring and inspection due to their unique force-electric coupling properties.Piezoelectric materials have problems such as brittleness and divergence of generated signals.Piezoelectric composites are widely used because they combine the good piezoelectric properties of piezoelectric crystals and the flexibility of polymers.The application range of composites with different connectivity is also different.Among them,1-3 composites are simple to prepare and are widely used in transducers and sensors.In this paper,by summarizing the research status of 1-3 composites and the problems in engineering,a microstructure design method based on the interface stress of composites was proposed,and the fatigue characteristics of the device were improved through the optimized design of piezoelectric composites.The research content and conclusions obtained in this paper are mainly divided into the following aspects:(1)The effect of interface stress on the properties of piezoelectric composites was explored,and the effects of different soft-filled polymers and polarization conditions on the dielectric and piezoelectric properties of conventional piezoelectric ceramic PZT(PbZr_1-xTi_xO₃,lead zirconate titanate)-based composites was studied.The optimized selection scheme and polarization conditions of the filled polymer was obtained.The research results showed that soft-filled polymers and high-temperature polarization conditions significantly improved the dielectric and piezoelectric properties of composites.(2)The influence of polarization temperature,cutting preparation process and composite design size on the dielectric and piezoelectric properties of piezoelectric single crystal PMN-PT(Pb(Mg_1/3Nb_2/3)O₃-xPbTiO₃,Lead magnesium niobate-lead titanate)-based composites was studied.The improvement of the polarization temperature and the preparation process and the optimization of the size scheme were proposed.The research results showed that the combination of high temperature 95°C polarization conditions with the preparation sequence of first polarization and then cutting and reduction of the slit size can achieve a win-win for the simplification of the preparation process and the high dielectric and piezoelectric properties(3)The elastic interaction between the two phases of the composite was studied,the stress state of the piezoelectric phase in the composite and its influence on the piezoelectric domain structure were obtained,and the COMSOL finite element simulation software was used to analyze the stress between the two phases in the composite.The research results showed that the normal stress and shear stress in the resin were the reasons for its polarity,which was consistent with the polarized light research results.In addition,the reduction in the size of the piezoelectric column lead to an increase in the interface stress,which was consistent with the experimental results.(4)The fatigue resistance of composite was researched.Through fatigue testing of single crystal and composite,explore the trend of the ferroelectric properties of the two with the number of cycles and the fatigue mechanism of the microstructure.The research results showed that the composite has much better fatigue resistance than single crystal.On the other hand,it was proposed to analyze the fatigue mechanism of the crystal from the perspective of microcracks and phase transition,and the mechanism of crack propagation and propagation was analyzed from the perspective of electrical breakdown and domain structure.The results showed that the growth trend of microcracks was consistent with the law of performance degradation.