1. China Jiliang University, Hangzhou, Zhejiang 310018, China
2. National Institute of Metrology, Beijing 100029, China
3. Xi'an Polytechnic University, Xi'an, Shannxi 710048, China
Abstract:Dislocation within platinum wire is one of the important factors affecting the stability of standard platinum resistance thermometers (SPRTs). From the microscopic point of view, the effect of annealing time on the dislocation density of platinum wire was studied by X-ray diffraction (XRD) analysis method, and verified by the SPRT annealing experimental data. The results show that the average dislocation density of the new platinum wire (purity 99.999%) with a diameter of 0.07mm goes down exponentially with the annealing time. After 100h annealing, the dislocation density decreases from 1012cm-2 to 1011cm-2, and then its dislocation density remains basically stable after 300h. The resistance of the new SPRTs have a significant decrease at the water triple point through previous 300h annealing, and the difference between before and after 300h annealing is less than 3mK and tends to be stable. The SPRTs annealing experiments and dislocation test results get good agreement at the heat treatment time. The research results provide technical support for the improvement of the standard platinum resistance thermometer manufacturing process and the revision of the metrological verification regulations.
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