Apparent Reduction in the Value of the d 33 Piezoelectric Coefficient in PZT Thick Films
Apparent Reduction in the Value of the d 33 Piezoelectric Coefficient in PZT Thick Films
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PZT厚膜中d 33 压电系数值明显降低
DOI：
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发表时间：
2002
期刊：
影响因子：
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通讯作者：
R. Whatmore
中科院分区：
文献类型：
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作者：
R. Dorey;R. Whatmore
使用复合溶胶凝胶技术制备了厚 PZT 薄膜（1 - 20 m），其中 PZT 粉末和 PZT 生产溶胶形成浆料并旋涂到硅晶片上。获得的最大相对介电常数约为可比较成分的块状 PZT 所表现出的相对介电常数的 80%。然而，d 33、f 和 e 31、f [1] 压电系数明显低于块状 PZT。已经提出，d 33, f 的测量值明显受到颗粒-颗粒旋转和基板夹紧的影响，导致极化效率降低，这也可能大大降低观察到的 e 31, f 值。具有高孔隙率的样品已显示出d 33 值降低。这是由于粒子-粒子桥的弯曲和剪切引起的 31 和 51 模式压电产生的电荷。通过监测复合薄膜的 (200)/(002) X 射线衍射 (XRD) 峰的位置和强度的变化，研究了基板夹持对 d 33、f 和极化的影响。发现基材的存在会引入平行于薄膜平面的拉伸应力，从而使晶胞变形。发现极化后的后续永久极化由于这些应力的存在而减少。如果要对厚膜材料进行器件应用建模，则强调在厚膜和块状陶瓷上测量的 d 33 值之间的差异特别重要。在尝试对器件行为进行建模时，不应使用厚膜压电系数（即组合膜-基板结构的压电系数）来代替材料压电系数。此类行为将不可避免地导致错误的结果。
Thick PZT films (1 - 20 m) have been prepared using a composite sol gel technique whereby PZT powder and a PZT producing sol are formed into a slurry and spin coated onto silicon wafers. The maximum relative permittivity obtained was approximately 80% of that exhibited by bulk PZT of comparable composition. However, the d 33, f and e 31, f [1] piezoelectric coefficients were shown to be significantly lower than that of bulk PZT. It has been proposed that the measured value of d 33, f is affected appreciably by particle-particle rotation and substrate clamping leading to reduced poling efficiency which may also greatly reduce the value of e 31, f observed. Samples with high levels of porosity have been shown to exhibit a reduced value of d 33 . This was attributed to 31 and 51 mode piezoelectrically generated charges caused by the bending and shearing of particle-particle bridges. The effect of substrate clamping, on d 33, f and poling, has been studied by monitoring the changes in position and intensity of the (200)/(002) X-ray diffraction (XRD) peaks of composite films. The presence of the substrate was found to introduce tensile stresses parallel to the film plane which distorted the unit cell. Subsequent permanent polarisation following poling was found to be reduced due to the presence of these stresses. The discrepancies between the values of d 33 measured on thick films and bulk ceramics were highlighted as being of particular importance if thick film materials are to be modelled for device applications. Thick film piezoelectric coefficients (i.e. those of the combined film-substrate structure) should not be used in place of material piezoelectric coefficients when attempting to model the behaviour of devices. Such actions would inevitably lead to erroneous results.