Effect of annealing atmosphere on the structure and dielectric properties of unfilled tungsten bronze ceramics Ba4PrFe0.5Nb9.5O30 |
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| Authors: | Zhe Guo Qihua Zhu Shan Wu Changzheng Hu Laijun Liu Liang Fang |
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| Affiliation: | Key Laboratory of New Processing Technology for Nonferrous Metals and Materials, Ministry of Education, Guangxi Universities Key Laboratory of Non-ferrous Metal Oxide Electronic Functional Materials and Devices, College of Material Science and Engineering, Guilin University of Technology, Guilin 541004, China |
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| Abstract: | Unfilled tungsten bronze ceramics with the nominal formula Ba4PrFe0.5Nb9.5O30 were synthesized via the standard solid-state sintering route, and the effects of oxygen vacancies on the dielectric and electrical properties were investigated in addition to the structure. Room-temperature X-ray diffraction showed that the N2-annealed sample had the largest cell volume. Low-temperature spectrum showed that N2 annealing rendered the dielectric constant and dielectric loss more frequency dispersive, whereas O2 annealing inhibited the frequency dispersion. The dc conductivity of all the samples originated from the electrons produced in the second ionization of oxygen vacancies and was most likely controlled by a mixed conduction mechanism of the electron and oxygen-vacancy ions. The N2-annealed sample has the highest dc conductivity owing to its high concentration of oxygen vacancies. The broadening of the Raman lines and the decrease of Raman intensity for the N2-annealed sample originated from a significant structural disorder. X-ray photoelectron spectra demonstrated that the increased oxygen vacancies caused by the change of valences of Fe and Pr ions contributed to the structural disorder. |
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| Keywords: | Tungsten bronze Annealing Structure Dielectric properties Electrical properties Mixed valence |
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