The ability to carry an electronic current is one of the most sensitive properties affected by structural changes and phase transitions in metals and alloys.
A one-piece device is described for determining the temperature and composition dependencies of the electric resistivity of fusible metals and alloys, over a wide range of compositions, under ultrahigh static vacuum. The latter factor is important when dealing with binary and ternary high-active melts of alkali metals releasing high-pressure saturated vapors.
Resistivity was measured by four-electrode potentiometer with the currents flowing in both directions. The spacing of the voltage electrodes was 7.5276 cm and the inner diameter of the glass capillary (charged, with the device remaining sealed with melts of the studied metals or their alloys) ~0.1109 cm. Measurement error ~0.4%.
A distinctive feature of the measurements in the phase-transition region was the longer thermostating time (not less than 1-1,5 hours) needed for completing the possible structural changes and achieving phase equilibrium in the specimens. By contrast, the temperature step was reduced to fractions of a degree for finer reading of the initial and final temperatures of the phase transitions. The process is suitable for multiple repetitions for each alloy, thereby providing the sought data for plotting the composition dependence of the resistivity at different temperatures.
Using the described device, we implemented the procedure on pure potassium and a series of its alloys with cesium, confirming the adequacy of the results in terms of reliability, accuracy, and agreement with literature data.