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Title: Crystal structure and electrical properties of Ca {sub x}WO{sub 3} (0.01 {<=} x {<=} 0.15) prepared by hybrid microwave synthesis

Abstract

Calcium tungsten bronzes Ca {sub x}WO{sub 3} (0.01 {<=} x {<=} 0.15) were synthesized by hybrid microwave method from mixtures of CaO, WO{sub 3} and tungsten powder. Single-phased samples can be obtained by microwave heating within 40 min. With the increase of calcium content, the crystal structure of Ca {sub x}WO{sub 3} transforms from orthorhombic (0.01 {<=} x {<=} 0.02) to tetragonal (0.03 {<=} x {<=} 0.11) and then to cubic (0.12 {<=} x {<=} 0.15). The average size of crystallites is in the range 1-5 {mu}m. All samples show semiconductor behaviour in their temperature dependence of resistivity. The electrical conduction mechanism changes from variable-range hopping to the thermally activated mechanism when x > 0.12.

Authors:
 [1];  [2];  [2];  [2];  [2]
  1. National Laboratory for Superconductivity, Institute of Physics, Chinese Academy of Sciences, P. O. Box 603, Beijing 100080 (China). E-mail: guojuan@ssc.iphy.ac.cn
  2. National Laboratory for Superconductivity, Institute of Physics, Chinese Academy of Sciences, P. O. Box 603, Beijing 100080 (China)
Publication Date:
OSTI Identifier:
20891650
Resource Type:
Journal Article
Resource Relation:
Journal Name: Materials Research Bulletin; Journal Volume: 41; Journal Issue: 3; Other Information: DOI: 10.1016/j.materresbull.2005.08.032; PII: S0025-5408(05)00336-3; Copyright (c) 2005 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; CALCIUM; CALCIUM OXIDES; CHEMICAL PREPARATION; ELECTRICAL PROPERTIES; MICROWAVE HEATING; MICROWAVE RADIATION; ORTHORHOMBIC LATTICES; SEMICONDUCTOR MATERIALS; TEMPERATURE DEPENDENCE; TUNGSTATES; TUNGSTEN; TUNGSTEN BRONZE; TUNGSTEN OXIDES; X-RAY DIFFRACTION

Citation Formats

Guo Juan, Dong Cheng, Yang Lihong, Fu Guangcai, and Chen Hong. Crystal structure and electrical properties of Ca {sub x}WO{sub 3} (0.01 {<=} x {<=} 0.15) prepared by hybrid microwave synthesis. United States: N. p., 2006. Web.
Guo Juan, Dong Cheng, Yang Lihong, Fu Guangcai, & Chen Hong. Crystal structure and electrical properties of Ca {sub x}WO{sub 3} (0.01 {<=} x {<=} 0.15) prepared by hybrid microwave synthesis. United States.
Guo Juan, Dong Cheng, Yang Lihong, Fu Guangcai, and Chen Hong. Thu . "Crystal structure and electrical properties of Ca {sub x}WO{sub 3} (0.01 {<=} x {<=} 0.15) prepared by hybrid microwave synthesis". United States. doi:.
@article{osti_20891650,
title = {Crystal structure and electrical properties of Ca {sub x}WO{sub 3} (0.01 {<=} x {<=} 0.15) prepared by hybrid microwave synthesis},
author = {Guo Juan and Dong Cheng and Yang Lihong and Fu Guangcai and Chen Hong},
abstractNote = {Calcium tungsten bronzes Ca {sub x}WO{sub 3} (0.01 {<=} x {<=} 0.15) were synthesized by hybrid microwave method from mixtures of CaO, WO{sub 3} and tungsten powder. Single-phased samples can be obtained by microwave heating within 40 min. With the increase of calcium content, the crystal structure of Ca {sub x}WO{sub 3} transforms from orthorhombic (0.01 {<=} x {<=} 0.02) to tetragonal (0.03 {<=} x {<=} 0.11) and then to cubic (0.12 {<=} x {<=} 0.15). The average size of crystallites is in the range 1-5 {mu}m. All samples show semiconductor behaviour in their temperature dependence of resistivity. The electrical conduction mechanism changes from variable-range hopping to the thermally activated mechanism when x > 0.12.},
doi = {},
journal = {Materials Research Bulletin},
number = 3,
volume = 41,
place = {United States},
year = {Thu Mar 09 00:00:00 EST 2006},
month = {Thu Mar 09 00:00:00 EST 2006}
}
  • Boron tungsten bronzes B {sub x}WO{sub 3} (0.01 {<=} x {<=} 0.08) were synthesized by hybrid microwave method from mixtures of WO{sub 3} and amorphous boron powder. With the increase of boron content, the crystal structure of B {sub x}WO{sub 3} transforms from orthorhombic (x = 0.01) to tetragonal {alpha} (x = 0.048) and then to tetragonal {beta} (0.07 {<=} x {<=} 0.08). The average size of crystallites is in the range of 1-10 {mu}m. All samples show semiconducting behaviour in their temperature dependence of resistivity. The conduction behaviour above 80 K for samples with x = 0.01 and 0.08more » can be explained using the variable-range hopping and thermally activated mechanism, respectively. Comparative experiments showed that boron bronze phases cannot be obtained by the microwave heating of pure WO{sub 3} powder or a mixture of B{sub 2}O{sub 3} and WO{sub 3} under the same conditions.« less
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