Journal
MATERIALS TODAY COMMUNICATIONS
Volume 33, Issue -, Pages -Publisher
ELSEVIER
DOI: 10.1016/j.mtcomm.2022.104712
Keywords
Niobates; Rietveld refinement; XPS; Dielectric constant; Electrical conductivity; Nyquist analysis
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Funding
- Ministry of Science and Higher Education of the Russian Federation [0852-2020-0032, BAS0110/20-3-08IF]
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Structural, microstructural, and electronic state investigations of NaNb1-xZrxO3 ceramics were performed. The ceramics showed orthorhombic phase structure and exhibited thermal hysteresis and polymorphic phase transition. The conduction mechanism was found to be related to oxygen vacancies and charge neutrality. These findings contribute to a better understanding of the physical properties and conduction behavior of this ceramic material.
NaNb1-xZrxO3 (NZr) ceramics with 0<0.15 are prepared via solid-state reaction route. Structural, microstruc-tural, and electronic state investigations of NZr samples were performed using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and X-ray photoelectron spectroscopy (XPS), respectively. Rietveld refinement reveals that NZr samples crystallize in the orthorhombic phase similar to room temperature Pbma phase of NaNbO3. Minor quantities of ZrO2 are detected for higher NZr-composition, which suppress the grain growth of NZr ceramics. XPS reveals that small amount of Zr substitution in NaNbO3 also creates an ambiance of unbalanced charge neutrality. The dielectric characteristics of NZr samples are investigated from -190 to 450 degrees C temperature range in frequency window 1 KHz-1 MHz for both the heating and cooling cycles. A clear thermal hysteresis loop is obtained in each composition and the observed anomaly corresponds to P (AFE) -R (AFE) polymorphic phase transition. As x grows, ' (T) becomes more dispersive and strongly depend on applied field. The activation energy obtained from the analysis of Arrhenius relation indicates that the oxygen vacancies are responsible for conduction process of the material. Impedance analysis confirms the NTCR behavior and non-Debye relaxation of the material.
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