STRUCTURAL AND DIELECTRIC CHARACTERIZATION OF CADMIUM TARTRATE

Polycrystalline samples of dimeric cadmium tartrate, [(Cd,C4H4O6)(2)H2 O](3)H2O [labeled CdT(I)], were studied using impedance measurements a nd x-ray powder diffraction. The dependence of the real part of the di electric constant on temperature showed a sharp peak at about 65 degre es C, revealing a structural phase transition, while the other broad p eak in the temperature range (70<T<85 degrees C) was due to the loss o f water molecules. The x-ray powder diffraction patterns at three temp eratures (25, 60, and 70 degrees C) are consistent with three nonequiv alent space groups. According to these results, it seems that this com pound undergoes two successive phase transitions: P2(1)2(1)2(1) --> P2 (1) --> Pnmn, suggesting an intermediate ferroelectric behavior, label ed CdT(II) between a paraelectric CdT(I) and an anhydrous phase, label ed CdT(III). (C) 1998 American Institute of Physics. [S0021-8979(98)03 722-0]