Dielectric Study on Czochralski Crystal of Ferroelectric Rb2CdI4

A single crystal of Rb2CdI4 obtained by Czochralski method was 20 mm in diameter and transparent with slightly yellowish appearance. Temperature dependence of the dielectric constant along the b-axis of this crystal also showed a lambda-type peak at the Curie temperature T-c and a shoulder-like anomaly around the T-s = 150 K. However the peak value of the dielectric constant at T-c was about 50,000. The dielectric anomaly around the T-s disappeared when the sample was polarized. The spontaneous polarization of this crystal measured by a pyroelectric method was 4.9 x 10(-2) C/m(2) at 4 K and was more than ten times of the Bridgeman crystal.