Three Terminal Capacitive Dilatometer

We designed Three Terminal Capacitance Dilalatometer (h=32mm, w=21mm) for low temperature thermal expansion measurements. Our data includes the measurement of themperature dependant capaitance and the conversion of capacitance to equivalent length change of the sample. The Dilatometer is tested by measuring the samples with known thermal expansion and compared with reported literature. The fractional length change data measured using our modified Dilatometer is in good agreement with reported one. Moreover, our design eliminate the use of kapton foil in the cell that contributes non-linearly to the thermal expansion and also does not require the use of an adhesive like Stycast which tends to crack after thermal cycling resulting in an electrical short between the capacitor plates and the cell body. We have used Alumina washers for providing insulation between the plates and the cell body.

本研究设计了一款尺寸为高度32mm、宽度21mm的三端电容热膨胀仪（Three Terminal Capacitance Dilalatometer），用于低温热膨胀测试。本数据集包含样品的温度依赖性电容测试数据，以及将电容值转换为样品等效长度变化量的相关结果。该热膨胀仪通过测试已知热膨胀系数的样品完成性能标定，并与已发表的文献数据进行对比验证。采用本改进型热膨胀仪测得的相对长度变化数据，与已发表的文献结果吻合度极佳。此外，本设计摒弃了以往腔体中使用的会对热膨胀产生非线性影响的Kapton箔，同时无需使用类似Stycast的胶粘剂——这类胶粘剂在热循环过程中易发生开裂，进而引发电容极板与腔体本体之间的电气短路。本设计采用氧化铝垫圈实现电容极板与腔体本体之间的绝缘。