Low-temperature heat capacity of NaNbO3 compound

The specific heat measurements of NaNbO3 crystals were carried out in the temperature range 4.5–278 K. The obtained data exhibit so-called non-Debye features at low temperatures and do not reveal any anomaly connected with antiferroelectric–ferroelectric phase transition. The experimental data are fitted and discussed with an expression containing the Debye and an Einstein contributions with ΘD=520, 612K and ΘE=183K for the low and high temperature phases, respectively. The presence of ≈T−2 term has been found in the lowest temperatures.