Effect of the Precipitation of Dissolved MnCl2on the Low-Temperature Thermal Conductivity of NaCl

Abstract

Low-temperature thermal conductivity measurements were made on NaCl crystals doped with ${10}^{-4\mathrm{}}$ mole fraction Mn${\mathrm{Cl}}_2$. The manganese ions were first quenched into approximate solid solution and then allowed to age at room temperature. Approximate kinetics of the precipitation that resulted were measured by electron spin resonance. There was surprisingly little change in the conductivity during aging; in particular a low-temperature decrease did not appear. The conclusion was that the presence of clusters cannot be invoked to explain the greater than Rayleigh scattering cross section often observed with point defects at low temperatures. The small conductivity changes that did result were: (1) a depression at temperatures near that of the conductivity maximum, and (2) a gradual rise at higher temperatures towards the values obtained with an undoped crystal. These changes were most rapid near the end of the clustering process and suggest a change in the nature of the precipitate at this stage.