SPECIFIC-HEAT OF BULKLIKE NIO POWDER FROM 14-K TO 280-K

The specific heat of a bulklike NiO powder sample has been measured from 14 to 280 K. Results have been compared with previous measurements below 20 K and above 60 K as well as with predictions from inelastic neutron scattering derived phonon density of states. These measurements fill in the temperature gap in specific heat data for NiO, provide a basis for future calorimetric studies of very fine powder NiO samples, and indicate inadequacies in the inelastic neutron scattering derived phonon density of states at frequencies in the neighborhood of 3 THz and below. An anomalous contribution to the heat capacity at about 25 K is attributed to magnetic ordering of impurity Ni(OH)2 constituting about 0.5% of the sample. © 1979 American Institute of Physics.