Impedance spectroscopy and permittivity study of (1-x)NBT-xBT ceramics

The complex impedance spectroscopy method was applied to evaluate the profound characteristics of the electrical transport capacity of lead-free ferroelectric ceramic solid solutions of (1-x) (Na0.5Bi0.5)TiO₃-xBa TiO₃ (NBT-xBT) (0.00 ≤ x ≤ 0.10). The elaboration of NBT-xBT, via a solid-state reaction between (Na0.5Bi0.5)TiO₃ and BaTiO₃, was determined using X-ray diffraction. Refinements, at room temperature, identified a rhombohedral phase, space group R3c for x=0.0 and 0.03, which possesses an antiphase, corresponding to the tilting system ā ā ā with an angle of inclination of 8.24° according to Glazers notation. We used the complex impedance, complex electric Cole-Cole diagram and frequency-dependent AC conductivity analysis to examine the relaxation and conduction mechanism in these samples, which exhibit non-Debye type behaviour. In addition, using an equivalent circuit composed of resistance and capacitance, we examined the different contributions (grains and grain boundaries) in our samples. (Na0.5Bi0.5)TiO₃ exhibits a dielectric resonance, which manifests itself as negative permittivity. The resonance development of NBT-xBT in the range (500Hz-2MHz) is discussed in this paper

DIELECTRIC MEASUREMENTS AND IMPEDANCE SPECTROSCOPY OF Ba-MODIFIED (Na 0.5Bi0.5)TiO₃ PREPARED BY THE HYDROTHERMAL METHOD

Sodium bismuth titanate (Na0.5Bi0.5)TiO₃ perovskite is presented as a lead-free concurrent for electro-ceramic engineering technologies. In this paper, (1-x)(Na0.5Bi0.5)TiO₃-xBaTiO₃ type ceramic materials were obtained by the hydrothermal process at a very low heat treatment temperature of around 200 ° C and for times up to 24 hours. The structural, microstructural, and dielectric properties of the ceramic materials were investigated. The X-ray diffraction analysis confirms the formation of the rhombohedral phase of NBT with space group R3c. Based on the Rietveld refinement, the morphotropic phase boundary (MPB) was determined for the composition x (%) = 5 and 7. The grains increase in size from 11 to 23 μm and their distribution widens with an increasing barium concentration in the morphotropic phase boundary. The dielectric constants were measured from room temperature to 600 °C for various frequencies in the range of 1 kHz - 2 MHz. From the Nyquist impedance plot, the effect of the grain and the grain boundaries on the electrical properties was studied. At high temperatures, the Uchino law modified by Echatoui et al. allows one to describe the thermal variation of the permittivity. This diffuse character is attributed to a cationic disorder due to the distribution of Na + /Bi 3+ and Ba 2+ ions in the A site