Effect of annealing on microstructure and properties of Pt wires used for standard Pt resistance thermometer

Abstract In this work, several measurement techniques were carried out to study the effect of annealing on the microstructure and properties of Pt wires used for the standard Pt resistance thermometer. Based on analysis of the relationship within dislocation density, nano-mechanical properties and resistance/resistivity, the effect of annealing on the resistance/resistivity of Pt wires was revealed. Traditional techniques cannot measure the resistance of fine Pt wires, and this work proved a new way to solve the problem. The results showed that the main impurities on the initial Pt wires were graphite and some compounds consisting of O, Ca, Mg, Si, Zn and N. During annealing, PtO2 particles were formed near the Pt grain boundaries and some holes were produced at the grain boundaries. When the annealing time was increased, the PtO2 particles broke down into elemental Pt and O2 and some compound impurities decomposed or even disappeared. Dislocations were the main affecting factor for the change of nanomechanical properties and resistance/resistivity of Pt wires. The dislocation density of Pt wires decreased when annealing time increased, which further led to the decrease of hardness and resistance/resistivity of Pt wires.