Journal
CERAMICS INTERNATIONAL
Volume 46, Issue 3, Pages 3759-3766Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.ceramint.2019.10.098
Keywords
Nb2O5 precursors; Phase structure; Ferroelectric performance; Dielectric properties; Thermal-expansion properties
Categories
Funding
- National Key R&D Program of China [2016YFB0402701, 2016YFA0201103]
- National Basic Research Program of China [2015CB654605]
- National Natural Science Foundation of China of China [51831010, 51672293, 11475240]
- Instrument Developing Project of Chinese Academy of Sciences [ZDKYYQ20180004]
- Chinese Academy of Sciences President's International Fellowship Initiative [2017VMA0018, 2011T2G03]
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NaNbO3 (NN)-based solid solutions show potential applications in energy storage capacitors, strain actuators, and electrocaloric cooling devices. However, NN ceramics with distinct structures, which are prepared using various Nb2O5 precursors, have not been studied. In this work, two types of Nb2O5 precursors were used, including coexisting orthorhombic and monoclinic phases (denoted as OM), and single orthorhombic phase (denoted as O). Phase structure, grain morphology, sintering characteristics, ferroelectric performance, dielectric properties, and thermal-expansion properties were systematically investigated. Rietveld refinement of XRD data revealed that synthesized and sintered samples showed different phase structures. The content of ferroelectric phase (Q phase, space group P2(1) ma) was 82.7% in synthesized NN-OM, whereas it was only 73.2% in synthesized NN-O; it was 33.8% in sintered NN-OM, while it was 18.6% in sintered NN-O. Raman spectra verified that the Q phase in NN-OM was more than that in NN-O. Curie temperature (T-c) of NN-OM was 363 degrees C, whereas T-c of NN-O was only 352 degrees C. Furthermore, compared with NN-O, NN-OM showed an inhomogeneous grain size distribution, lower optimum sintering temperature, higher phase transition temperature, stronger ferroelectric performance, and larger thermal-expansion displacement. Therefore, crystal structure of Nb2O5 has a great influence on the structure and performances of NN ceramics.
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