Pyroelectricity of Molecular Crystals: Benzene Derivatives

Abstract

The pyroelectric coefficient at constant stress was measured for meta-nitroaniline, meta-amino-phenol, and 2,3-dichlorophenol in the temperature range 90 ≦ T/K ⪅ melting point. A change in sign of the pyroelectric coefficient was observed in meta-nitroaniline and 2,3-dichlorophenol. At room temperature [FORMULA OMITTED] is 9 µCm−2 K−1 for meta-nitroaniline, 42 µCm−2 K−l for meta-aminophenol, and 0.3 µCm−2Kr−1 for 2,3-dichlorophenol (at 263 K for the latter one). By a classical harmonic oscillator model the contribution to the pyroelectric coefficient due to molecular dipole librational motions was estimated to be fairly small for meta-nitroaniline. The temperature dependence of the coefficient of meta-nitroaniline is discussed on the basis of Boguslawski’s theory. The importance of internal polar optical modes for the temperature dependence of the pyroelectric coefficient of molecular crystals is shown. © 1985, Walter de Gruyter. All rights reserved.