Structural study and temperature dependent relaxation and conduction mechanism of orthorhombic tungsten bronze Ba4La28/3(Zr0.05Ti0.95)18O54 ceramic

Abstract

• The structure and impedance properties have been studied for the Ba 4 La 28/3 (Zr 0.05 Ti 0.95 ) 18 O 54 ceramic. • The formula of the developed model [ B a 4 − a □ a ] A 2 [ L a 8 + 2 b 3 □ 2 − 2 b 3 ] A 1 , A 1 ′ ( Z r 0.05 T i 0.95 ) 18 O 54 is described as perovskite layers with 3 octahedral thickness parallel to the xOz plane. • The contribution of grains and grain boundaries was verified by analysis of the Nyquist plots and complex modulus study. • The activation energies calculated from the conduction and relaxation mechanisms are almost identical for the Ba 4 La 28/3 (Zr 0.05 Ti 0.95 ) 18 O 54 ceramic. In this study, the Ba 4 La 28/3 (Zr 0.05 Ti 0.95 ) 18 O 54 ceramic was prepared using the solid-state technique. The X-ray diffraction technique was used in this study to investigate the Ba/La order in the solid solution Ba 4 La 28/3 (Zr 0.05 Ti 0.95 ) 18 O 54 . We have developed a structural model, to represent the order within the structure. The formula of model [ B a 4 − a □ a ] A 2 [ L a 8 + 2 b 3 □ 2 − 2 b 3 ] A 1 , A 1 ′ ( Z r 0.05 T i 0.95 ) 18 O 54 is described as perovskite layers with a thickness of 3 octahedral parallel to the xOz plane. Scanning electron microscopy (SEM) showed that Ba 4 La 28/3 (Zr 0.05 Ti 0.95 ) 18 O 54 ceramic exhibits a typical columnar grain with a heterogeneous distribution over the entire surface. Complex impedance spectroscopy was used to analyze the dielectric and electrical properties of Ba 4 La 28/3 (Zr 0.05 Ti 0.95 ) 18 O 54 materials over a frequency range of 10 Hz to 1 MHz and a temperature range of 350°C to 400°C. An appropriate equivalent electrical circuit was also used to investigate the contributions of grains and grain boundaries. The AC-conductivity data was analyzed using Jonscher's universal power law. The thermal behavior of the exponent parameter "s" indicates that the dominant conduction mechanism in our compound is the non-overlapping small polaron tunneling (NSPT) model. The activation energies calculated from the conduction and relaxation mechanisms are nearly identical for the Ba 4 La 28/3 (Zr 0.05 Ti 0.95 ) 18 O 54 ceramic.