Sol-gel auto-combustion synthesis of KxNa1-xNbO3 nanopowders and ceramics: Dielectric and piezoelectric properties
(1. Key Laboratory of Phytochemistry of Shaanxi Province, College of Chemistry and Chemical Engineering, Baoji University of Arts and Sciences, Baoji 721013, China;
2. State Key Laboratory of Solidification Processing, School of Materials Science and Engineering Northwestern Polytechnical University, Xi’an 710072, China;
3. Science College, Air Force Engineering University, Xi’an 710051, China)
2. State Key Laboratory of Solidification Processing, School of Materials Science and Engineering Northwestern Polytechnical University, Xi’an 710072, China;
3. Science College, Air Force Engineering University, Xi’an 710051, China)
Abstract: The KxNa1-xNbO3 nanopowders with cubic-like morphology and an average size of about 50 nm were synthesized by sol-gel auto-combustion method. And then, the ceramics were prepared and the phase transition, microstructure and electrical properties of the KxNa1-xNbO3 ceramics were investigated. Pure perovskite phases of the KxNa1-xNbO3 ceramics were confirmed by XRD patterns and the K0.50Na0.50NbO3 ceramics show the coexistence of orthorhombic and monoclinic structures. SEM micrographs show that all samples have bimodal grain size distributions and the number of the small grains decrease with increasing K+ content in the bimodal grain size distribution system. The K0.50Na0.50NbO3 ceramics with the uniform grain size and the maximum density show excellent electrical properties with εr=467.40, tan δ=0.020, d33=128 pC/N and kp=0.32 at the room temperature, demonstrating that the properties of the K0.50Na0.50NbO3 powers prepared by sol-gel auto-combustion are excellent and the ceramics are promising lead-free piezoelectric materials.
Key words: sol-gel auto-combustion; KxNa1-xNbO3; phase transition; microstructure; electrical properties