An investigation of phonon scattering by chromous ions in MgO by thermal conductivity measurements

Abstract

The effects of X -irradiation, thermoluminescence and heat treatment on the thermal conductivity principally between 1 and 4 °K of nominally pure and Cr-doped MgO have been examined. It is concluded that the Cr2+ion produced by X -irradiation is responsible for the very strong excess phonon scattering. An analysis of the data shows that the scattering has both resonant and non-resonant components and that if the non-resonant component is proportional to concentration, the resonant component is proportional to the square root of the concentration indicating the existence of cooperative effects. The resonant scattering occurs atca. 4 cm-1in reasonable agreement with the calculated energy separation 5.6 cm-1of theEandA2levels of Cr2+(Fletcher & Stevens 1968). The work also indicates that the thermal conductivity at 4.2 °K provides a useful method of determining the Cr2+concentration in MgO.