| Piezoelectric ceramics are widely used in high-k capacitors,piezoelectric transducers,positive temperature coefficient components,high displacement piezoelectric actuators,nano piezoelectric ceramics,optical limiters and medical ultrasonic composite materials.They have become the core of biomedical,aerospace,electronic information,ammunition engineering and other fields.The continuous research on formula,process,morphology,performance and other aspects makes the increasingly mature piezoelectric ceramic industry always keep "young",and more widely used in various fields.In the field of ammunition,piezoelectric ceramics are more and more used in fuzes.It is an urgent problem to improve the low-temperature storage and low-temperature environmental adaptability of piezoelectric ceramic power supply.In this paper,PZT-5H at-40℃～25℃ was studied,the static electrical parameters of PZT-5H at different temperatures were measured firstly,then,the mechanical and electrical coupling experimental system of low temperature piezoelectric ceramics under impact load is established,and PZT-5H mechanical and electrical coupling experiments are carried out under different temperatures,different impact velocities and different loads,based on the theories of mechanical and electrical failure,engineering thermodynamics,mechanical domain switching and material mechanics,the mechanism of impact force electric coupling of low temperature piezoelectric ceramics was studied finally.The main research results are as follows:For the static electrical properties of low temperature piezoelectric ceramics,when the temperature of PZT-5H drops from 25℃ to-40℃,the resistivity and relative permittivity of PZT-5H decrease.According to the dielectric theory,the principle that resistivity decreases with temperature is explained,and the relaxation time of PZT-5H in the range of-40～25℃ is deduced by Debye’s model.As the temperature decreases,the electromechanical coupling coefficient increases linearly,the energy barrier and the coercive electric field increase,while the electromechanical coupling behavior decreases and the residual polarization decreases.The results show that the influence of impact velocity on the dynamic piezoelectric voltage constant increases with the decrease of temperature.The energy density of the discharge generated by impact on PZT-5H only accounts for about 1 ‰ of the irrecoverable energy density under the condition of electrical short circuit.The variation of the peak discharge energy of the energy storage capacitor with temperature is similar to that of the accumulated energy with temperature under the condition of electrical short circuit.Combined with scanning electron microscope,it is observed from the microscopic point of view that when the piezoelectric ceramics are impacted by the Hopkinson rod,the porosity defects and cracks at the fracture place have obvious influence on the electrical output characteristics of piezoelectric ceramics.Through the analysis of space charge theory,the freezing effect of piezoelectric ceramics caused by the obstruction of domain motion at low temperature is obtained.The domain switching strain of PZT-5H was calculated by X-ray diffraction,and the domain switching of PZT-5H at different temperatures was analyzed.Based on ABAQUS simulation software,the numerical simulation of low temperature piezoelectric ceramics under open circuit loading of Hopkinson system is carried out.The numerical simulation results of dynamic response and open circuit discharge characteristics of low-temperature piezoelectric ceramics are analyzed compared with the experimental results.The reliability of numerical simulation under low-temperature conditions is verified by the results of impact coupling experiment of low-temperature piezoelectric ceramics under open circuit,and the experiment is saved It also provides a theoretical basis for the future research on the mechanical and electrical coupling of dielectric materials at low temperature. |
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