Temperature and pressure dependence of dielectric properties of ceramic Pb(Fe/sub 1/2/Ta/sub 1/2/)O/sub 3/

摘要

Dielectric properties such as the real epsilon " and imaginary epsilon " parts of the complex permittivity and the spontaneous polarization P/sub N/ of ceramic Pb(Fe/sub 1/2/Ta/sub 1/2/)O/sub 3/ with the diffuse phase transition (DPT) were measured under pressures up to 6 kbar. The value of epsilon " shows a broad maximum at a temperature T/sub m/ (mean Curie temperature). As the pressure increases, T/sub m/ of the maximum epsilon " ( epsilon "/sub max/) and the value of epsilon "/sub max/ decrease, and the shape of the maximum in epsilon " around T/sub m/ becomes broader. The pressure coefficient of T/sub m/ is about -3.4 K/kbar. The small heat effect associated with the DPT was observed around T/sub m/. The temperature and pressure dependence of epsilon " and P/sub s/ is 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 25 K and increases with increasing pressure.