The role of salts selection on phase formation and electrical properties of K0.5Bi0.5TiO3 ceramics fabricated via molten salt synthesis

• Published in: Materials chemistry and physics 2022-05, Vol.283, p.126017, Article 126017
• Main Authors: Badole, Manish, Dwivedi, Sushmita, Vasavan, Hari Narayanan, Kumar, Sunil
• Format: Article
• Language: English
• Subjects: Bismuth compounds; Bismuth titanate; Ceramics; Chemical composition; Crystal structure; Dielectric behavior; Electrical properties; Energy dispersive X ray analysis; Grain size; Lead-free piezoceramics; Molten salt synthesis; Molten salts; Perovskite structure; Piezoelectricity; Potassium chloride; Reaction kinetics; Room temperature; Stoichiometry; Synthesis; Temperature dependence; Thermal conductivity; X ray analysis
• ISSN: 0254-0584; 1879-3312
• DOI: 10.1016/j.matchemphys.2022.126017

The present study reveals the effect of salts (NaCl and KCl) on the chemical composition, structural, and electrical properties of intended K0.5Bi0.5TiO3 (KBT) ceramics fabricated via the molten salt synthesis (MSS) route. The average grain size (∼6 μm (±1.1 μm)) and elemental distribution observed by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX) on KBT ceramics prepared using NaCl as the salt (named KBT-Na) signify the formation of Na0.5Bi0.5TiO3 (NBT) phase instead of KBT ceramic. The Rietveld refinement on X-ray diffraction (XRD) data and temperature-dependent dielectric behaviour of KBT-Na sample further validate the formation of NBT phase. The obtained results suggest the reaction of NaCl salt during the MSS of the KBT-Na sample. Moreover, the structural analyses of KBT ceramic synthesized using KCl salt (named KBT-K) suggested the presence of a minor Aurivillius phase (K0.5Bi4.5Ti4O15) which could be related to undesired reaction kinetics in MSS. The higher room temperature conductivity (∼10−6 Scm−1) and lower piezoelectric coefficient ((d33) ∼ 4–5 pC/N) indicate the loss of stoichiometry in both KBT-Na and KBT-K ceramics during the removal of salts. The observed results in KBT-Na & KBT-K were systematically compared with pure NBT & KBT ceramics prepared using the conventional solid-state synthesis route. The possible reasons for the lossy behavior of MSS synthesized samples are also discussed. •Effect of NaCl and KCl molten salts on the K0.5Bi0.5TiO3 phase formation is studied.•Na0.5Bi0.5TiO3 phase, rather than the intended K0.5Bi0.5TiO3, formed in NaCl flux.•Significant degradation of electrical properties was observed in molten salt synthesized ceramics.