Dielectric and Pyroelectric Properties of Lithium Hydrogen Dimalate, LiH3(C4H4O5)2

Abstract

The dielectric constant and the pyroelectric coefficient at constant stress of 1-lithium hydrogen dimalate 1-Li⊕(OOCCHOHCH2COOH)⊖(HOOCCHOHCH2COOH), were investigated in the temperature range 200 ≦ T / K ≦ Td (decomposition temperature) and 100 ≦ T / K ≦ Td, respectively. The compound crystallizes in the space group P21. In the direction of the 21 axis ε'22 increases with almost constant slope with increasing temperature from 7.32 (200 K) to 8.55 (360 K). The pyroelectric coefficient p2 shows a maximum at 152 K and a minimum at 290 K; p2 lies between 15 μC m-2 K-1 and 6 μC m-2 K-1. The contribution of the lattice to the polarization was calculated on the basis of a point charge model developed from a charge distribution calculation on the INDO basis. Assuming certain lattice vibration frequencies and a harmonic oscillator model, p2 = ƒ(T) was calculated. Qualitatively the calculations are in satisfactory agreement with the experiment.