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• 作者：Pascal Roussel ; Daniel Groult ; Antoine Maignan ; and Philippe Labbé
• 刊名：Chemistry of Materials
• 出版年：1999
• 出版时间：August 1999
• 年：1999
• 卷：11
• 期：8
• 页码：2049 - 2056
• 全文大小：278K
• 年卷期：v.11,no.8(August 1999)
• ISSN：1520-5002

文摘

Phase relations in the system Na-K-P-W-O have been studied for two values m = 4and m = 6 of the relevant parameter m which characterizes the thickness of the perovskiteWO₃-type slabs within the series of the low dimensional tungsten phosphate bronzes (K_xNa_y)(PO₂)₄(WO₃)_2m. New Na_yP₄W₁₂O₄₄ bronzes (0ages/entities/le.gif"> y ages/entities/le.gif"> 1) belonging to the monophosphatetungsten bronzes with pentagonal tunnels family have been isolated and studied by single-crystal X-ray diffraction and resistivity measurements. The crystal structure of Na_0.96P₄W₁₂O₄₄has been solved and refined to conventional R = 0.0289 (wR = 0.0414) with 2924 reflectionswith I ages/entities/ge.gif"> 3ages/gifchars/sigma.gif" BORDER=0 >(I). Like that of P₄W₁₂O₄₄, the unit cell is orthorhombic (space group P2₁2₁2₁)with a = 5.3083(3) Å, b = 6.5790(7) Å, and c = 23.6360(10) Å. The location of Na⁺ cationsin the O₁₈ cages with pentagonal windows is compared to that of Na⁺ cations in the O₁₈cages with hexagonal windows of the monophosphate tungsten bronzes with hexagonaltunnels Na_1.7P₄W₁₂O₄₄. Electron transport properties of single crystals of both monophosphatetungsten bronzes with pentagonal and hexagonal tunnels are described and discussed interms of possible charge density wave (CDW) instabilities.