Dielectric Study on Czochralski Crystal of Ferroelectric Rb2CdI4

A single crystal of Rb 2 CdI 4 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 λ -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× 10 –2 C/m 2 at 4 K and was more than ten times of the Bridgeman crystal.