Co-Doping Effect of BiGaO 3 and (Bi,Na,K,Li)ZrO 3 on Multi-Phase Structure and Piezoelectric Properties of (K,Na)NbO 3 Lead-Free Ceramics

Min-Ku Lee, Sang-Don Bu and Gyoung-Ja Lee
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Min-Ku Lee: Nuclear Materials Development Division, Korea Atomic Energy Research Institute, Daejeon 34057, Korea
Sang-Don Bu: Department of Physics and Research Institute of Physics and Chemistry, Chonbuk National University, Jeonju 54896, Korea
Gyoung-Ja Lee: Nuclear Materials Development Division, Korea Atomic Energy Research Institute, Daejeon 34057, Korea

Energies, 2019, vol. 12, issue 5, 1-10

Abstract: The phase boundary structure of (K,Na)NbO 3 piezoelectric ceramic was modified by doping with Bi(Na,K,Li)ZrO 3 and BiGaO 3 through normal solid-state sintering. Rietveld refinements by X-ray diffraction revealed that the Bi(Na,K,Li)ZrO 3 /BiGaO 3 co-doping in (K,Na)NbO 3 led to a multi-phase structure at room-temperature, effectively moving the rhombohedral-orthorhombic (R-O) and orthorhombic-tetragonal (O-T) polymorphic phase transition temperatures close to the room temperature region. Increased levels of doping also generated a structural transition, i.e., triphasic R-O-T to diphasic R-T (T-rich) and finally to R-T (R-rich), contributing to shrinkage of the O phase as well as the increase of R phase fraction. A sensitive influence of the BiGaO 3 doping (0.001 mole fraction level) on the structural properties such as the phase and microstructure was shown, resulting from the effect of the super-tetragonal structure of BiGaO 3 . The d 33 property was strongly dependent on the phase and its volume fraction, in addition to the grain sizes. Eventually, enhanced and balanced properties of the piezoelectric coefficient and Curie temperature ( d 33 = 309 pC/N, T C = 343 °C) were obtained when the doped ceramic had a T-rich (86%) R-T structure.

Keywords: lead-free piezoelectric ceramics; potassium-sodium niobate (KNN); phase boundary structure; phase fraction (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2019
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