Structural, dielectric and impedance spectroscopy analysis of Ba 5 CaTi 1.94 Zn 0.06 Nb 8 O 30 ferroelectric ceramic.

In this work, Zn co-doped tungsten bronze having nominal formula Ba 5 CaTi 1.94 Zn 0.06 Nb 8 O 30 has been synthesized and systematically studied for structure, dielectric and electrical properties. The formation of the phase of tetragonal tungsten bronze with space group P 4 bm and the occurrence of oxygen vacancies were verified by the Rietveld refinement using X-ray diffraction data. Scanning electron microscopy (SEM) of Ba 5 CaTi 1.94 Zn 0.06 Nb 8 O 30 ceramic shows high densification, low porosity, and homogeneous distribution of grains of different sizes over the total surface. The sample shows a dielectric anomaly of ferroelectric paraelectric type at 262 °C, and has non-relaxor type of diffuse phase transition. The electrical property (complex impedance Z *, complex permittivity ε *, complex modulus M *) of Ba 5 CaTi 1.94 Zn 0.06 Nb 8 O 30 ceramic has been investigated by non-destructive complex impedance spectroscopy (CIS) as a function of frequency at different temperatures. Grains and grain boundaries conduction is detected from a complex impedance spectrum by fitting the Nyquist plot with an appropriate electrical circuit. The Nyquist plot indicates the negative temperature coefficient of resistance (NTCR) character of Ba 5 CaTi 1.94 Zn 0.06 Nb 8 O 30 ceramic. The variation of AC conductivity as a function of frequency reveals that the compound has an Arrhenius-type behavior of electrical conductivity. The DC electrical conductivities of grains and grain boundaries have been studied. The presence of non-Debye relaxations was verified by a complex modulus analysis.