  In this work structural refinement, complex impedance spectroscopy, and Raman
spectroscopy have been investigated on
Na$_{0.5}$(Bi$_{1-x}$Dy$_x$)$_{0.5}$TiO$_3$ (xDyNBT) ceramic systems. The pure
NBT, 2DyNBT and 5DyNBT compounds crystallize in a rhombohedral structure while
the 15DyNBT composition crystallizes in an orthorhombic Pnma structure. We
reported that dysprosium addition affects the phase transition temperatures as
well as the dielectric losses. The electrical transport at high temperatures
was investigated using the CIS over a wide frequency range. The studied samples
showed a non-Debye type process, with a short-range relaxation for the pure NBT
and a coexistence of both localized and long-range relaxations of charge
carriers for the 2DyNBT and 5DyNBT compounds. For the high concentration,
15DyNBT, a short-range relaxation is observed. Moreover, using a brick-layer
model we discuss the resistance and capacitance of the different contributors
(grain and grain boundaries) in our samples. High temperature Raman
spectroscopy investigation was performed in order to follow the temperature
evolution of the structural transformations on ferroelectric compounds.
Anomalies in the temperature evolution of the vibrational modes are seen to
correlate well with the temperature transitions observed from dielectric
measurements.
