Dielectric Properties of Synthetic Diamond Polycrystals

The temperature and frequency dependences of the dielectric properties, electrical conductivity, and complex impedance of polycrystalline samples sintered from synthetic diamond powder under a pressure of 8 GPa with different temperatures are studied. The sample obtained at a higher temperature has a higher electrical conductivity which arises from conduction along intergrain boundaries, a higher value of dielectric constant, and a stronger dispersion due to the distributed capacitance that occurs during the formation of charge carrier depleted layers at the interface of media with different conductivity. The analysis of complex impedance by the method of equivalent circuits showed that intergrain boundaries exert a dominant influence on these polycrystalline samples at room temperature.