电容式薄膜应变计的研制

发布时间：2018-05-07 06:39

本文选题：电容式应变计 + 钛酸锶钡薄膜　；参考：《电子科技大学》2016年硕士论文

【摘要】：应变计在各种零部件的力学性能以及力学行为研究中发挥着重要的作用。目前,应变计大部分是基于压阻效应,即电阻随应变的变化而成比例变化。电阻式应变计在高温环境下易氧化,稳定性、可靠性较差,不能满足航天、航空核电等领域高温环境下的应用需求。而电容式应变计的应变敏感介质一般采用介质材料,具有更好的高温稳定性和高温下抗干扰能力。本研究采用钛酸锶钡(Ba0.5Sr0.5TiO3,BST)作为电容应变计的应变敏感介质,由于BST的介电常数对应变敏感,有可能提高其应变灵敏系数。本论文通过射频磁控溅射镀膜技术和微细加工技术,研制了采用BST薄膜作为应变敏感层的BST电容应变计,并与以氧化铝(Al2O3)作为应变敏感层的Al2O3电容应变计进行对比,研究了其应变敏感特性、介电特性和温度特性。主要研究内容和结果如下:1.设计并制备了平面插指结构的电容式BST薄膜应变计。采用射频磁控溅射的方法制备了BST薄膜,采用直流溅射的方法制备了PdCr电极,并通过光刻剥离工艺实现插指电极的图形化。2.对电容式BST薄膜应变计的频率性能和温度性能进行了研究。结果表明,当频率在100 kHz附近时,应变计的电容值较为稳定,且介电损耗很小,因此在此频率下测试电容应变计的性能较合适。BST电容应变计的电容随着温度的增加先降低后增加,其电容温度系数(TCC)由负变为正。3.对电容式BST薄膜应变计和Al2O3应变计的应变敏感性能进行了对比研究。首先采用悬臂梁结构对应变计的挠曲应变敏感性能进行了测试。结果表明,对于BST电容应变计,由于应变的增加会导致BST薄膜介电常数增加,从而使其电容值增加,测得应变灵敏度(GF因子)是3.13,滞后性(?Hm)的最大值为8.9%。对于Al2O3电容应变计,应变的增加会导致插指电极间距增加,其电容值减小,测得GF因子为-3.4,滞后性?Hm的值为11.5%。然后采用Zwick拉伸机对应变计的剪切应变敏感性能进行了测试。结果表明,BST应变计的GF因子是2,Al2O3应变计的GF因子是-10.8。挠曲应变和剪切应变下测得的GF因子趋势一致但大小不同,其原因可能是,由于BST薄膜的各向异性,BST材料的介电常数对挠曲应变更敏感,采用悬臂梁结构测试的GF因子更大,而剪切应变对插指电极间距的影响更大,造成使用拉伸结构测试的Al2O3电容应变计的GF因子更大。
[Abstract]:Strain gauge plays an important role in the study of mechanical properties and mechanical behavior of various parts. At present, the strain gauge is mostly based on the piezoresistive effect, that is, the resistance changes proportionally with the strain. The resistive strain gauge is easy to be oxidized, stable and reliable in high temperature environment. It can not meet the application requirements of aerospace, aviation nuclear power and other high temperature environment. The strain sensitive medium of capacitive strain gauge generally adopts dielectric material, which has better high temperature stability and anti-interference ability at high temperature. In this study, barium strontium titanate Ba0.5Sr0.5TiO3BST was used as the strain sensitive medium of the capacitance strain gauge. Because the dielectric constant of BST is sensitive to strain, the strain sensitivity coefficient may be improved. In this paper, BST capacitive strain gauge using BST thin film as strain sensitive layer is developed by RF magnetron sputtering coating technology and micro fabrication technology, and compared with Al2O3 capacitor strain gauge with Al 2O 3 as strain sensitive layer. The strain sensitivity, dielectric and temperature characteristics are studied. The main contents and results are as follows: 1. A capacitive BST thin film strain gauge with planar insertion structure was designed and fabricated. BST thin films were prepared by RF magnetron sputtering and PdCr electrodes were prepared by DC sputtering. The frequency and temperature properties of capacitive BST film strain gauge are studied. The results show that the capacitance of the strain gauge is stable and the dielectric loss is very small when the frequency is around 100 kHz. Therefore, the performance of the capacitance strain gauge measured at this frequency is more suitable. The capacitance of the capacitance strain gauge decreases first and then increases with the increase of temperature, and the capacitance temperature coefficient (TCCs) changes from negative to positive. 3. The strain sensitivity of capacitive BST film strain gauge and Al2O3 strain gauge were studied. First, the flexural strain sensitivity of the strain gauge is measured by cantilever beam structure. The results show that for BST capacitive strain gauge, the dielectric constant of BST film will increase because of the increase of strain. The measured strain sensitivity factor (GF) is 3.13, and the maximum value of lag Hm is 8.9%. For Al2O3 capacitive strain gauge, the increase of strain will lead to the increase of the electrode spacing and the decrease of the capacitance. The measured GF factor is -3.4, and the hysteresis Hm is 11.5. Then the shear strain sensitivity of the strain gauge was tested by Zwick extender. The results showed that the GF factor of BST strain gauge was -10.8. The trend of GF factor measured under flexural strain and shear strain is the same but different, which may be due to the fact that the dielectric constant of anisotropic BST films is more sensitive to flexural strain, and the GF factor measured by cantilever beam structure is larger. The effect of shear strain on the intercalation electrode spacing is greater, and the GF factor of Al2O3 capacitive strain gauge tested by tensile structure is larger.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TH823.3

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