Studies of Crystal Structure, Dielectric, Ferroelectric and Piezoelectric Properties of K0.5Na0.5NbO3-BiScO3 Ferroelectric Solid Solutions

Abstract

Ferroelectric and piezoelectric materials have received significant attention of the scientific community because of their wide device applications. Due to the toxicity of lead, lead-free perovskite materials are now the focus of research and development. Potassium sodium niobate K0.5Na0.5NbO3 (KNN) is a promising lead-free candidate due to its high Curie temperature and ferroelectric properties. However, it has drawbacks such as highly hygroscopic constituent alkali components and moderate piezoelectric effect (d33 60 pC/N). To address these issues, solid solutions of KNN with the perovskite system BiScO3 were fabricated as Bi3+ being isoelectronic with Pb2+, can hybridise with O2- resulting in a lone pair which increases curie temperature and piezoelectric property. In the present investigation, we have studied the composition and temperature driven phase transition behaviour of solid solution of KNN with BiScO3. Polycrystalline ceramics (1-x) K0.5Na0.5NbO3-xBiScO3, where x = 0.000, 0.005, 0.010, 0.015, 0.020, 0.030, 0.040, 0.050 is prepared via conventional solid-state reaction technique. The X-ray diffraction, SEM micrographs, Raman scattering studies, temperature dependent dielectric, and piezoelectric properties were studied over wide range of experimental conditions. Formation of single perovskite phase is confirmed by XRD. Composition driven phase transition has been studied using both X-ray diffraction analysis and Raman spectroscopic studies. Rietveld refinement has been carried out with appropriate crystallographic model by observing pseudo-cubic reflections. The temperature driven phase transition was obtained for each composition using dielectric measurements. Piezoelectric coefficient maximized (d33 154 pC/N) for x = 0.015 which is more than double of undoped KNN. Further details will be part of presentation.