The pressure and temperature dependence of the dielectric properties of Pb(Co1/3Nb2/3)O3

The dielectric properties, such as the real in ' and imaginary in " parts of the complex permittivity and the spontaneous polarisation P s of single-crystal and ceramic Pb(Co 1/3 Nb 2/3 )O 3 with a diffuse phase transition (DPT), were measured under various pressures up to 6 kbar. The value of in ' shows a broad maximum in ' max at a temperature T m (mean Curie temperature). As the pressure increases, in ' max and T m decrease, and the shape of in ' around T m becomes somewhat sharper. The pressure coefficient of T m is about -3.54 K kbar -1 for the ceramic and -3.0 K kbar -1 for the single-crystal sample. The temperature and pressure dependence of in ' and P s are explained in terms of a phenomenological theory using statistical treatments based on a Gaussian distribution of the local Curie temperature. The value of the standard deviation sigma , describing the intensity of the DPT, is 56 K for the ceramic and 47 K for the single-crystal sample, and decreases with increasing pressure.