Pyroelectric and dielectric properties of potassium hydrogen phthalate single crystals

Abstract

Single crystals of potassium hydrogen phthalate, commonly known as potassium acid phthalate (KAP) have been grown from aqueous solutions. The dielectric constant, loss tangent, specific heat and pyroelectric coefficient were determined as a function of temperature. Frequency response of the dielectric constant and tan delta has been studied over a frequency range of 1-100 kHz. It is found that both the dielectric constant and tan delta decreases with increase in frequency. Anomalies in the dielectric constant and tan delta have been observed in the vicinity of decomposition temperature. The specific heat (C_p) and the pyroelectric coefficient have been determined as a function of temperature. The pyroelectric coefficient is found to increase gradually with increase in temperature up to about 440 K and it is consistent with the variation of C_p with temperature. The figure of merit which has been calculated at 320 K by combining pyroelectric, dielectric and thermal properties of the crystal is 1.79^∗10⁻⁹ C cm J⁻¹.