Dielectric response and thermistor behavior of lead-free x NaNbO3 - (1-x) BiFeO3 electroceramics
| Autor: | Y. Saad, María Luisa Osete López, Inmaculada Álvarez-Serrano, Mourad Hidouri |
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| Rok vydání: | 2018 |
| Předmět: |
010302 applied physics
Materials science Condensed matter physics Process Chemistry and Technology Diffusion 02 engineering and technology Activation energy 021001 nanoscience & nanotechnology Polaron 01 natural sciences Surfaces Coatings and Films Electronic Optical and Magnetic Materials Electrical resistivity and conductivity 0103 physical sciences Materials Chemistry Ceramics and Composites Orthorhombic crystal system Charge carrier Electroceramics 0210 nano-technology Temperature coefficient |
| Zdroj: | Ceramics International. 44:18560-18570 |
| ISSN: | 0272-8842 |
| Popis: | The electroceramics of the x NaNbO 3 - (1-x) BiFeO 3 (x = 0.15, 0.25, 0.50, 0.75, 0.85, 1) system (NBNFO) have been prepared at moderate temperatures (600 °C). Microstructural analysis from high resolution electron microscopy reveals the existence of small crystals (10–150 nm), which agglomerate leading to micro-sized crystals. All the NBNFO compounds show perovskite-type structure and a transition from rhombohedral (S.G. R 3 c ) to orthorhombic (S. G. P 2 1 ma ) mean macroscopic symmetry takes place for x = 0.50, as analyzed by refinement of XRD data. Nevertheless, at the microstructural scale, the system can be described by a compositional-segregation picture in which structural heterogeneity is present. The materials show a positive temperature coefficient of resistivity (PTCR)-thermistor behavior above room temperature for x ≥ 0.50, up to maxima temperature values of 410, 393, 405 and 463 K for x values of 0.50, 0.75, 0.85 and 1, respectively. Above these temperatures, in the NTCR temperatures-region, conduction and polarization phenomena are analyzed from impedance and modulus formalisms in terms of two mechanisms implying different charge carriers: polaron hopping and/or diffusion of cation and oxygen vacancies. The activation energy values, E a , corresponding to these processes are of about 0.50 and 1 eV, respectively. Finally, in the dielectric response displayed by the NBNFO ceramics, the development of a FE contribution as x increases is detected, which can be interpreted considering microstructural features. |
| Databáze: | OpenAIRE |
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