Functional Piezocrystal Characterisation under Varying Conditions.
Functional Piezocrystal Characterisation under Varying Conditions.
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DOI：
10.3390/ma8125456
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发表时间：
2015-12-02
期刊：
影响因子：
--
通讯作者：
Cochran S
中科院分区：
文献类型：
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作者：
Liao X;Qiu Z;Jiang T;Sadiq MR;Huang Z;Demore CEM;Cochran S
压电晶体，特别是基于弛豫的铁电晶体，在过去的三十年里受到了强烈的研究和发展，这是由于它们比压电陶瓷具有超高的压电系数和更高的机电耦合系数所提供的性能优势。压电晶体的结构各向异性也为器件在新的振动模式下工作提供了机会，例如d36面剪切模式，通过域工程和特殊的晶体切割。这些压晶特性有助于它们在低功率和高功率超声应用中的广泛应用。在这些应用中，传统的压电材料目前受到不同的机械应力/压力、温度和电场条件的影响。然而，正如前面所观察到的，压电晶体的性能受到单一或多种条件的显著影响。因此，在这些条件下对压电晶体特性的实验室表征对于充分理解这些材料和在现实情况下设计电声换能器至关重要。这将有助于确定这些高性能压电晶体在要求苛刻的应用中取代传统压电陶瓷的程度。然而，这样的特征需要特定的实验安排，这里报告了其中的例子，以及相关的结果。测量包括在机械应力0-60 MPa，温度20-200℃，高电交流驱动和直流偏压下的压电材料的高频分辨率阻抗谱。激光多普勒测振仪和红外热像仪也集成到测量系统中，用于振动模态扫描和高交流驱动的热调节。已经测试了三代压晶：(1)二元，PMN-PT；（II）三元，PIN-PMN-PT；（III）掺杂三元，Mn:PIN-PMN-PT。利用谐振模式分析，分析了弹性、介电常数和压电常数以及耦合系数的变化，并进行了热调节测试，以评估高功率条件下压电晶体的稳定性。
Piezocrystals, especially the relaxor-based ferroelectric crystals, have been subject to intense investigation and development within the past three decades, motivated by the performance advantages offered by their ultrahigh piezoelectric coefficients and higher electromechanical coupling coefficients than piezoceramics. Structural anisotropy of piezocrystals also provides opportunities for devices to operate in novel vibration modes, such as the d36 face shear mode, with domain engineering and special crystal cuts. These piezocrystal characteristics contribute to their potential usage in a wide range of low- and high-power ultrasound applications. In such applications, conventional piezoelectric materials are presently subject to varying mechanical stress/pressure, temperature and electric field conditions. However, as observed previously, piezocrystal properties are significantly affected by a single such condition or a combination of conditions. Laboratory characterisation of the piezocrystal properties under these conditions is therefore essential to fully understand these materials and to allow electroacoustic transducer design in realistic scenarios. This will help to establish the extent to which these high performance piezocrystals can replace conventional piezoceramics in demanding applications. However, such characterisation requires specific experimental arrangements, examples of which are reported here, along with relevant results. The measurements include high frequency-resolution impedance spectroscopy with the piezocrystal material under mechanical stress 0–60 MPa, temperature 20–200 °C, high electric AC drive and DC bias. A laser Doppler vibrometer and infrared thermal camera are also integrated into the measurement system for vibration mode shape scanning and thermal conditioning with high AC drive. Three generations of piezocrystal have been tested: (I) binary, PMN-PT; (II) ternary, PIN-PMN-PT; and (III) doped ternary, Mn:PIN-PMN-PT. Utilising resonant mode analysis, variations in elastic, dielectric and piezoelectric constants and coupling coefficients have been analysed, and tests with thermal conditioning have been carried out to assess the stability of the piezocrystals under high power conditions.