Heat capacity of Ce0.8Y0.2O1.9 and the effects of dissolution of water/hydrogen

The heat capacity of polycrystalline Ce0.8Y0.2O1.9 and of its water/hydrogen-dissolved sample was measured from 6 to 300 K using an adiabatic calorimeter. The heat capacity of the water/hydrogen-dissolved sample is larger than that of the dry sample below 50 K, and the difference is about 10% at 10 K. Such a difference should originate in the change of lattice vibration spectra caused by the introduction of water/hydrogen. The mechanism is discussed in terms of the defect structure.