Dielectric and Pyroelectric Properties of Lithium Hydrogen Dimalate,

The dielectric constant and the pyroelectric coefficient at constant stress of 1-lithium hydrogen dimalate l-Li®(OOCCHOHCH 2CO O H )e (HOOCCHOHCH2COOH), were investigated in the temperature range 200 S 77K ^ Td (decomposition temperature) and 100 ^ T/K ^ Td, respec­ tively. The compound crystallizes in the space group P2j. In the direction of the 2, axis £22 increases with almost constant slope with increasing temperature from 7.32 (200 K) to 8.55 (360 K). The pyroelectric coefficient p 2 shows a maximum at 152 K and a minimum at 290 K; p2 lies between 15 n C m 2 K -1 and 6 n C m 2 K -1. The contribution of the lattice to the polar­ ization 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, p 2 = f ( T ) was calculated. Qualitatively the calculations are in satisfactory agreement with the experiment.