LOW-TEMPERATURE THERMAL-PROPERTIES OF PBI2

The heat capacity and thermal conductivity of a large (56.5 g) crystal of PbI2 have been measured in the temperature region 0.5 < T < 3.9°K. Analysis of the heat capacity data yields a value of the limiting apparent Debye characteristic temperature θ0c = 99.4 (±0.3)°K, which corresponds to an average lattice wave velocity of 1.151 (±0.005) × 105 cm sec-1. It is consistent with a wave velocity estimated from neutron scattering experiments, but not with one determined from Brillouin spectra. The heat capacity data also show that dispersion of the low frequency waves is not unusual, as might have been expected for a layer-type crystal. The apparent thermal conduction is found to be surprisingly small in the crystal. © 1979.