The surface layer effect in TS, KDP and Rochelle salt

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Abstract
The surface layer effect in triglycine sulphate (TGS), potassium dihydrogen phosphate (KDP) and Rochelle salt (RS) has been investigated by measuring the thickness dependence of the dielectric constant. Measurements at and near the transition temperatures have been made at a frequency of 1 kHz. The sample thickness has been varied between about 3 and 0.2 mm. The measured dielectric constant is found to decrease with the sample thickness for all the three materials and the effect is more pronounced for the smaller thicknesses (less than 1 mm). The results can be explained by considering a single homogeneous surface layer of low dielectric constant and the thickness and dielectric constant of the surface layer are independent of temperature. The surface layer thickness is found to be of the order of 10-4 cm for Rochelle salt and 10-5 cm for KDP and TGS.