Linear and volume thermal expansions of ferroelectric NaNO2

The linear thermal expansions x(i) (i = a, b, c) of ferroelectric NaNO2 single crystals were measured by means of a clip-type dilatometer using four strain gauge elements below 460 K down to liquid helium temperature. In this work, the coefficients alpha(i) (i = a, b, c) of linear thermal expansions showed anomalies at the Curie temperatures T-C = 437.6 K and the Neel temperature T-N = 438.8 K on heating. The coefficient beta of volume thermal expansion showed the clear lambda-type anomaly around the T-N and the sharp peaks around the T-C. In the latter case the beta changed complicatedly.