Dielectric studies on Sm-modified two-layered BLSF ceramics

Abstract

Sm x Bi 3−x TiNbO 9 (SBTN) with x = 0, 0.2, 0.4, 0.6, 0.8 and 1.0, a novel type of ceramic was prepared by a conventional solid-state reaction method. X-ray diffraction patterns confirm the formation of a single-phase, and lattice parameters were calculated based on the parent compound Bi 3 TiNbO 9 (BTN). Well-defined grains were seen in the scanning electron microscopy pictures. A kink observed near 400 • C for all the samples in the dielectric plot as well as in the stretched exponential parameter (β) vs. temperature plot reveals the dielectric relaxation of the samples. The tolerance factor (t) was found to increase with increase in the size of the A-site (Bi-site) modified ion (Sm). Impedance and modulus spectroscopic studies were conducted to understand the plausible reason for the dielectric relaxation. The relaxation was found to be well-fit with Arrhenius equation. SBTN samples showed lower dielectric loss compared to BTN. The remnant polarization, obtained from experimental, was found to be less than that of theoretically calculated polarization, using Shimakawa's formula. The proposed defect mechanism was interpreted using FTIR and Raman spectroscopic studies.

Voigt Profile is Suitable for Impedance Spectroscopic Analysis of BLSF Ceramics

“…In addition, intergrowth (x BSLT -(1-x) BGLT, where x = 0.49, sample C) and solid solution (BSLT -BGLT, sample D) ceramics were prepared. Detailed synthesis and the lattice parameters were described elsewhere [11,16]. The impedance measurements were made by Hewlett-Packard (HP4192A) impedance analyzer.…”

“…These vacancies accumulated at the grain boundaries act as an opposite polarizing process. Hence, they may result in broad peaks near 450 °C in all the samples [11,16]. Moreover, the multiple rare-earth ionic incorporation at the bismuth site creates more vacancies on complex defect dipoles owing to the electron hopping process in singly or doubly ionized vacancies (Kroger-Vink reaction).…”

“…Generally, the dielectric relaxation peaks give information about the competitive interaction of both long-range and short-range ordering that are present in the sample. The same information can be extracted from the specified peak shape and its width [11]. Spectroscopic peaks are generally described either by Gaussian or Lorentzian fitting [6,12].…”