Studies on the compositional dependent structural and electrical properties of CaTiO3-modified K0.5Na0.5NbO3 piezoelectric system

Sahoo, S and Pradhan, DK and Kumari, S and Sahu, A and Samantaray, KS and Singh, C and Mishra, A and Rahaman, MM and Kumar, A and Thomas, R and Rack, PD and Pradhan, DK (2024) Studies on the compositional dependent structural and electrical properties of CaTiO3-modified K0.5Na0.5NbO3 piezoelectric system. In: Journal of Applied Physics, 135 (24).

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Abstract

Lead-free piezoelectric ceramics of (1 � x)K0.5Na0.5NbO3-xCaTiO3 were fabricated, and their crystal structure, microstructure, and electrical properties were systematically studied. Rietveld refinement of the x-ray diffraction data and Raman spectroscopic analyses revealed a composition-dependent structural phase transition: three phase transitions, namely, from a pure orthorhombic phase for x � 0.02 to a mixed phase of orthorhombic and tetragonal phases (0.03 � x � 0.08) and finally another mixed phase of tetragonal + cubic for x = 0.10 and 0.15 at room temperature (RT). The morphological study reveals a decrease in grain size along with a more uniform distribution of grains as the concentration of CaTiO3 (CT) increases; notably, a homogeneous distribution of grains is observed for x = 0.05. The temperature-dependent dielectric properties show two phase transitions, from orthorhombic to tetragonal (TO-T) and tetragonal to cubic (TC), for unmodified K0.5Na0.5NbO3 (KNN). However, both the phase transition temperatures (TO-T and TC) decrease, and the transition peaks broaden with an increase in CT substitution, and for x > 0.06, the TO-T shifted below RT. The broadening of the transition peak at TO-T may be due to the relaxation behavior. Among the prepared samples, the 5 mol. CT-modified KNN shows the optimum electrical properties (d33= 114 pC/N, �r= 412, and 2Pr= 15.25 μC/cm2) at RT. The enhanced electrical properties for x = 0.05 are due to the coexistence of orthorhombic and tetragonal phases, facilitating easy polarization rotation and flattening of the free energy profile. A phase diagram has been constructed based on the information gathered from the temperature-dependent dielectric measurements, RT x-ray diffraction, and Raman spectroscopy data and is discussed in detail. © 2024 Author(s).

Item Type:	Journal Article
Publication:	Journal of Applied Physics
Publisher:	American Institute of Physics
Additional Information:	The copyright for this article belongs to American Institute of Physics.
Keywords:	Crystal structure; Free energy; Perovskite; Phase diagrams; Phase transitions; Piezoelectric ceramics; Piezoelectricity; Raman spectroscopy; Rietveld refinement; Room temperature; Sodium compounds; Spectroscopic analysis, Crystals structures; Distribution of grains; Lead-free piezoelectric ceramic; Mixed phase; Orthorhombic phase; Piezoelectric system; Structural and electrical properties; Temperature dependent; Tetragonal phase; Transition peaks, Niobium compounds
Department/Centre:	Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited:	18 Dec 2024 07:17
Last Modified:	18 Dec 2024 07:17
URI:	http://eprints.iisc.ac.in/id/eprint/85851

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