Microconfigured piezoelectric artificial materials for hydrophones

Piezoelectric PZT–air composites with a complex design optimized for hydrophones were fabricated as arrays of hundreds of 60 μ units using a microfabrication technique involving coextrusion of mixtures of thermoplastic with PZT powder or carbon powder. The measured piezoelectric coefficient was 300 pC/N with a figure of merit of 18 pm²/N, in excellent agreement with the predicted properties.     

Transverse sensitivity of piezoelectric accelerometric transducers

Conclusions The transverse sensitivity of piezoelectric acceleration transducers is caused by the lack of coincidence between the transducer's sensitivity axis and the polarization vector of the piezoelectric plate. This fact should be taken into consideration both in the production of piezoelectric elements, and in the design of transducers and their manufacture.     

纵振型低频压电水听器的等效电路及有限元分析对比研究

分别利用等效电路理论与ANSYS有限元仿真对纵振型复合棒式压电水听器的性能参数进行了计算,并将两种结果进行比对分析。对比发现两种分析方法得出的接收灵敏度最大值对应的频率不在同一处并且在数值上存在一定差异,在远离谐振点的较低频段,水听器的接收灵敏度都具有较为平坦的响应。等效电路理论只考虑了一维纵向振动并且将模型完全理想化,而ANSYS有限元分析则考虑了整个结构的纵向横向模态耦合,其建模更接近实际模型,因此ANSYS有限元分析在水听器的仿真优化设计中更符合实际情况,但还需制作实物,用实测结果进行比对。等效电路理论由于物理意义明显,可以为水听器设计和有限元仿真提供理论指导。     

Enhancement of piezoelectric properties and temperature stability by forming an MPB in KNN-based lead-free ceramics

0.92(Na_0.51K_0.49?x Li _x )NbO₃–0.02Bi_0.5K_0.5TiO₃–0.06BaZrO₃ (x = 0, 0.01, 0.02, 0.03, 0.04, and 0.05) lead-free piezoelectric ceramics were prepared by solid state reaction route. The effect of Li doping amount on the structure and electrical properties of the ceramics were investigated. All ceramics had pure perovskite structure, while the crystallographic symmetry changed from rhombohedral to tetragonal with the increase of Li doping amount. A PZT-like morphotropic phase boundary (MPB) with the coexistence of rhombohedral and tetragonal phases was identified in the composition of x = 0.03. As expected, the ceramics of the MPB composition showed optimal properties: piezoelectric coefficient d ₃₃ = 227 pC/N, planar electromechanical coupling coefficient k _p = 39.3 %, dielectric permittivity $ \varepsilon_{33}^{T} /\varepsilon_{0} $  = 1,640, dielectric loss tanδ = 2.0 %, remnant polarization P _r = 13.3 μC/cm², coercive field E _c = 1.53 kV/mm, and Curie temperature T _c = 253 °C. Together with good temperature stability to 200 °C, this KNN-based lead-free ceramics should be very promising for practical applications.     

Measurement of piezoelectric modulus by pulsed excitation of piezoelectric ceramic elements

The possibility of measuring the piezoelectric modulus by exciting piezoelectric ceramic components with a radio pulse is considered. It is shown that there is a relation between the piezoelectric modulus and the rate of change of the current envelope at the beginning of the transient. Theoretical relations are derived. __________ Translated from Izmeritel’naya Tekhnika, No. 10, pp. 71–72, October, 2006.     

Measurement of high temperature phase stability and thermophysical properties of alloy 740

In the present study, the characterisation of phase stability and measurement of different thermophysical properties of alloy 740 has been carried out. The transformation temperatures including liquidus/solidus and corresponding enthalpy of transformation have been measured for different phase changes up to melting using dynamic calorimetry. Further, the enthalpy increment data have been measured in the temperature range of 473–1473?K to obtain the heat capacity using static calorimetry. The present calorimetric data have been analysed in corroboration with the results obtained using JMatPro and Thermo-Calc simulation. In addition, the temperature dependence of other thermophysical properties such as thermal expansivity, density, thermal diffusivity and thermal conductivity are also measured in the range of 300–1473?K using thermomechanical analyser and laser flash method.     

参数激励非线性压电梁的振动稳定性

研究了参数激励压电梁的振动稳定性,考虑非线性阻尼的影响,采用Hamilton变分原理推导结构运动方程,采用多尺度法求解稳态响应幅值。通过数值算例分析了电压、轴向力以及非线性阻尼等因素对定常解稳定性的影响。通过分析可见,外加电压与压电层上下表面电势差的差值△V主要影响自变量σ／ω的取值区间,对定常解的稳定性影响较小;梁所承受的轴力越小,定常解稳定区间越大;非线性阻尼的常数项和二次项系数越大,定常解稳定区间越大。     

Automatic calibration of the recording-channel sensitivity in piezoelectric measuring systems

Conclusions The above calibration circuit is suitable for obtaining by a simple method the instantaneous sensitivity of recording channels in piezoelectric installations at the instant of recording the process.The error due to connecting the calibrator circuit across the piezoelectric transducer input does not exceed the errors produced by other elements of the recording channel.The calibrating pulse amplitude U(l _k) is determined by the stabilitron's stabilized voltage and the ratio of capacitances C_k and Translated from Izmeritel'naya Tekhnika, No. 12, pp. 77–78, December, 1966.     

A high sensitivity hydrostatic piezoelectric transducer based ontransverse piezoelectric mode honeycomb ceramic composites

A new piezoelectric composite transducer based on the ceramic honeycomb structure is introduced. The transducer is operated in the transverse piezoelectric (TP) d₃₁ mode. The ceramic honeycomb configuration enables one to fabricate a TP honeycomb transducer by either embedding a honeycomb ceramic skeleton into a soft polymer matrix to form a composite or by blocking the openings of the honeycomb cells with thin layers of epoxy to form an end-capped honeycomb structure. With the unique honeycomb configuration and TP operation mode, the piezoelectric d₃₃ response of the ceramic is nearly eliminated and the piezoelectric responses from the three orthogonal directions add together when the transducer is subjected to a hydrostatic pressure. As a result, the transducer exhibits exceptionally high hydrostatic piezoelectric response     

温度和湿度对聚四氟乙烯多孔驻极体膜压电活性稳定性的影响

研究了具有开放性孔洞的聚四氟乙烯(voided polytetrafluoroethylene,PTFE)多孔膜和PP蜂窝膜(polypropylene cellular)的驻极体行为和压电活性的温度效应。研究结果指出：和PP蜂窝膜驻极体相比．PTFE多孔膜驻极体呈现出突出的电荷储存和压电活性的温度稳定性;研究了这类稳定性的驻极体和材料的结构根源。PTFE多孔薄膜驻板体这种压电活性的温度稳定性主要依赖于这类驻极体材料电荷储存及材料的本征性能(如力学性质等)的温度稳定性。实验结果还说明：PTFE多孔膜突出的压电系数温度稳定性使它大大扩展了以包括PP在内的空间电荷型多孔膜研制的压电功能元器件的耐温要求。本文还讨论了环境因素(如相对湿度)对这类功能膜压电活性的影响,分析了环境湿度对压电活性影响的结构根源。     

Measurement of oxygen recombination rate constants by the piezoelectric method

The piezoelectric method is used to measure pressure in a gas flow within a nozzle, measurement results are compared with calculation, and values of the oxygen atom recombination rate constant are obtained for the temperature range 1680–3250°K.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 53, No. 3, pp. 437–441, September, 1987.