Effect of surface capacitance on the dielectric behavior of triglycine selenate near the transition temperature

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Abstract
The dielectric constant of triglycine selenate (TGSe) has been measured at 1 kHz, for different crystal thicknesses (in the range 3-0.3 mm) over a wide temperature range to cover both ferroelectric and paraelectric regions. Measurements have been made on different samples using silver-conducting paint and evaporated gold as electrodes. The peak value of the dielectric constant near the transition temperature first decreases slowly and then rapidly with decreasing thickness of the crystal. The results can be explained by assuming a single surface layer of low dielectric constant (∼ 4.5) and a few hundred angstroms (≃400 Å) thick. These parameters are independent of temperature. The surface-layer thickness shows little dependence on the electrode material, but even when the preparation conditions and electrode material are kept the same, the numerical values show a wide variation (more than a factor of 2) for samples from different batches.