Abstract: The 18nm ZnO ultrafine powders with the wurtzite phase were prepared by using a new method of liquidoid
precipitation, and characterized by XRD, TEM. The heat capacities of the powder in 78-370K were also measured with a high precision automatic
adiabatic calorimeter and compared with that of the coarse crystal powders cited from literature. The relation between heat capacities and grain sizes
of the nano ZnO powders was demonstrated in the view of energetics. The results obtained show that the distribution of the nano ZnO powders is narrow,
and their purity is more then 99.9%. The polynomal equation fitted expressing the change of heat capacities with temperatures is C_p=
40.042+24.554X+0.93033X²+2.1649X³-1.8389X⁴.

Key words: nanometer ZnO, wurtzite phase, liquidoid precipitation method, low-temperature heat capacity