Research On High Power Piezoelectric Ceramic Materials And Its Testing System

Piezoelectric ceramic,which relates mechanical energy and electrical energy,is widely used in non-destructive testing,piezoelectric driving,ultrasonic diagnosis,hydroacoustic transduction and other fields.Piezo devices often require a high mechanical quality factor（Q_m）to obtain a large output power.However,the determination of the Q_m value is usually done with an impedance analyzer at a low applied voltage（1V）.The Q_m value obtained by this test method is inconsistent with the actual demand.This thesis mainly focuses on how to improve the value of Q_m and realize high power test of piezoelectric ceramics,analyzing the equivalent circuit model of the piezoelectric vibrator and the theoretical calculation method of mechanical quality factor（Q_m）,studying the effect of manganese（Mn）doped neutral and hard Pb（Zr,Ti）O₃（PZT）based piezoelectric ceramics on the structure and performance,exploring the piezoelectric ceramic high-power characteristics of the test principle,developing a high-power test system,and then in-depth studying of piezoelectric ceramic high-power characteristics change with vibration speed Characteristics.In this thesis,the equivalent circuit model of piezoelectric ceramics and the derivation process of mechanical quality factor were first studied.In this part,the equivalent model of piezoelectric ceramics is sorted out and standardized.The classical model and the dynamic model complement each other,which more intuitively show the working mechanism of piezoelectric ceramics.In addition,based on the equivalent model of piezoelectric ceramics,the two methods of mechanical quality factor（Definition method and 3d B method）are theoretically analyzed and compared experimentally.It was found that the two calculation methods are theoretically consistent.The comparison of experimental results also confirms the credibility of this theoretical derivation.The effect of MnCO₃ on the phase structure,microstructure and electrical properties of Pb（Zr,Ti）O₃ based piezoelectric ceramics was systematically studied.It was found that the hard behavior of MnCO₃ doping can greatly improve the mechanical quality factor（The value of Q_m increased by nearly 8 times）.In addition,the introduction of sintering aids Li Bi O₂ and Cu O make the composition achieve low-temperature sintering（900 ^oC）.The MnCO₃ doped ceramic samples have good temperature stability and low average power consumption,which are suitable for the preparation of high-power ceramic devices.The experiment also studied the effect of size on the phase structure and performance of piezoelectric ceramics.The low impedance characteristics of large-sized piezoelectric ceramics make its Q_m value much larger than that of small-sized piezoelectric ceramics.Similarly,MnCO₃ was used to dope modification of hard PZT-based piezoelectric ceramics.It was found that when the amount of MnCO₃ addition was0.2 wt%,the piezoelectric constant,k_p and Q_m achieved the optimal values at the same time,d₃₃～194 p C/N,d^*₃₃～260 pm/V,k_p～0.410,Q_m～2064.Adding sintering aids Li Bi O₂ and Cu O,d₃₃ and k_p increased from 194 p C/N and 0.410 to 218 p C/N and0.449,respectively.Q_m decreased slightly,from 2064 to 1613.In addition,the addition of an appropriate amount of Ce O₂ refines the grain size and improves the density of the sample.Based on the dynamic equivalent model of piezoelectric vibrator,a"three-step method"test procedure is proposed for the pulse driving method,which improves the accuracy of the test.At the same time,the problem of synchronous triggering and voltage signal amplification quality were studied.Operating software was developed independently based on Lab VIEW language.The multi-frequency（resonance and anti-resonance frequency）and multi-mode（p-mode and 31-mode）of the high-Q_mmaterials prepared above were measured by the test system to obtain the change curves of the Q_m value with the vibration speed.The accuracy of the test system is verified by comparing the test data with the results in the literature.