The giant and negative dielectric tunability of Pb(Fe1/2Nb1/2)1-xTixO3 single crystals is reported. A low field of 120 V/cm can induce a great reduction of the capacitance, and the tunability is larger than 80% in low frequency range (<1 MHz) at room
temperature. This giant tunability is ascribed to the interfacial polarization at the interface of electrode/sample. A negative dielectric tunability detected only in the tetragonal sample can be also attributed to the interfacial polarization. The origin of the giant and negative tunabilities is discussed with the multipolarization-mechanism model and equivalent circuit model, respectively.
We investigated the dielectric properties of Pb(Fe1/2Nb1/2)1-xTixO3 single crystals below room temperature. Two dielectric anomalies were detected in sample A while only one was detected in sample B in the temperature range 90~300 K. A Debye-like rel
axation with strong frequency dispersion was detected in both samples. The pre-edge XAFS suggests that this dielectric anomaly is induced by the hopping conductivity between Fe2+ and Fe3+. The EXAFS results give us a clear picture of the local structure of iron ions. The weak frequency dependent dielectric anomaly only observed in sample A is supposed to be due to the dipole glass behavior.
