Electrical conductivity and local structure of lithium iron tungsten vanadate glass |
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Authors: | Koken Matsuda Shiro Kubuki Kazuhiko Akiyama Zoltán Homonnay Ernő Kuzmann Tetsuaki Nishida |
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Affiliation: | 1. Department of Chemistry, Graduate School of Science and Engineering, Tokyo Metropolitan University, Minami-Osawa 1-1, Hachi-Oji, Tokyo, 192-0397, Japan 2. Laboratory of Nuclear Chemistry, Institute of Chemistry, E?tv?s Loránd University, Pázmany P. s., 1/A, Budapest, 1117, Hungary 3. Department of Biological and Environmental Chemistry, Faculty of Humanity-Oriented Science and Engineering, Kinki University, Kayanomori 11-6, Iizuka, Fukuoka, 820-8555, Japan
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Abstract: | A relationship between physical properties and local structure of 20Li2O·10Fe2O3·xWO3·(70–x)V2O5 glass, abbreviated as xLFWV glass (x?=?0???25 in mol%), was investigated by 57Fe-Mössbauer spectroscopy, Fourier transform infrared spectroscopy (FT-IR), differential thermal analysis (DTA), leaching test using 20 vol% HCl and DC two- or four-probe method. 57Fe-Mössbauer spectra of xLFWV glass showed an increase of quadrupole splitting (Δ) from 0.67 to 0.73±0.02 mm s???1 and a constant isomer shift (δ) of 0.39±0.01 mm s???1 with an increase of ‘x’ from 0 to 25. This suggests that FeIIIO4 tetrahedra gradually increase their local distortion along with a substitution of WO3 for V2O5. DTA of xLFWV glass showed an increase in glass transition temperature (T g) from 252 to 298 $_{pm 5}^{circ}$ C with an increase of ‘x’. Composition dependency of T g and Δ indicates that FeIII atoms occupy substitutional sites of WO6 octahedra as network former (NWF), since a large slope of 680 K (mm s???1)???1 was obtained in T g ? Δ plot. Comparable electrical conductivities (σ) of 2.5 × 10???6, 1.9 × 10???6, 8.4 × 10???7 and 2.9 × 10???6 S cm???1 obtained for xLFWV glasses with ‘x’ of 0, 10, 20 and 25, respectively increased to 2.4 × 10???2, 2.4 × 10???3, 3.5 × 10???4 and 8.8 × 10???5 S cm???1 after annealing at 400 °C for 100 min. Smaller Δ values of 0.58 and 0.67±0.02 mm s???1 obtained in annealed xLFWV glasses with ‘x’ of 0 and 10, respectively indicate that structural relaxation occurs in VO4 units of vanadate glass units, as had been observed in other vanadate glasses. |
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