Diffuse phase transition and impedance spectroscopy analysis of Ba2.15−x Na0.7+x Nb5−x W x O15 (x = 0.25) ferroelectric ceramic

Abstract

A new rare earth ferroelectric tetragonal tungsten bronze compound with general formula Ba 2.15-xNa 0.7?x Nb 5-x W x O 15 (x = 0.25) was elaborated as ceramic and investigated using X-ray diffraction and dielectric measurements. The results show a tetragonal phase with the space group P4bm. Special emphasis was done to characterize diffuse phase transition (DPT) that occurs close to 472°C. Using dielectric measurements in a frequency range of (10 Hz-1 MHz) and in a temperature range (25-550°C), we have shown that the real part of the permittivity close to DPT is well described by Santos-Eiras phenomenological model. Space charge polarization, relaxation phenomena and free charges conductivity have been analyzed using dielectric, impedance spectroscopy and Nyquist plots showed non-Debye (polydispersive) type relaxation. In paraelectric phase, the Arrhenius activation energies were determined. Frequency dependence of ac conductivity at different temperatures follows the Jonscher's universal law (Jonscher et al. in J Mater Sci 20:4431, 1985).

Crystallographic, Structural, and Electrical Properties of W6+ Substituted with Mo6+ in Crystalline Phases such as TTB Structure

“…Currently, the advancement of solid solutions has resulted in a multitude of varied distributions of metal cations across different crystallographic locations. This has the potential to enhance physical characteristics, such as dielectric and ferroelectric abilities [14,15]. Several approaches have been developed for enhancing either the structures or properties of ceramics.…”