New Evidence on the Structure of Potassium Salts of 12-Tungstophosphoric Acid, KxH3-xPW12O40
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- 作者：Jerzy Haber ; Leszek Matachowski ; Dariusz Mucha ; Jerzy Stoch ; and Priit Sarv
- 刊名：Inorganic Chemistry
- 出版年：2005
- 出版时间：September 19, 2005
- 年：2005
- 卷：44
- 期：19
- 页码：6695 - 6703
- 全文大小：184K
- 年卷期：v.44,no.19(September 19, 2005)
- ISSN：1520-510X
文摘
Physicochemical properties and compositions of KxH3-xPW12O40 salts, where 2 
x 3, have been investigated.It has been found that freshly prepared K2HPW12O40 salt (drying at 313 K) contains particles of heteropolyacid andparticles of the neutral potassium salt, the sample being in 78.6% amorphous. On aging at room temperature, theheteropolyacid spreads to form a surface layer covering the neutral potassium salt particles K3PW12O40. Heattreatment of KxH3-xPW12O40 salts, where 2 x < 3, from 313 K to higher temperatures induces the transformationof the heteropolyacid-covering K3 core into a well-dispersed, amorphous surface layer. On further heating of theacidic potassium salts, the surface layer decomposes between 855 and 915 K with the formation of a PW8O26-typebronze as a new phase, the K3PW12O40 salt remaining unchanged. The latter starts to decompose at 1093 K, andin the case of all samples, the process is completed at about 1183 K. Rietveld structure refinement, XPS, and 31PNMR measurements of acidic potassium salts indicate that the core of these salts is always formed by the K3PW12O40salt, which is covered by a heteropolyacid. Comparison of lattice parameters of the K3 salt and HPW leads to theconclusion that the layer is composed of partially or completely dehydrated heteropolyacid molecules. The coverageof the core by HPW in the K2 sample was estimated to be equal to one monolayer.
x 3, have been investigated.It has been found that freshly prepared K2HPW12O40 salt (drying at 313 K) contains particles of heteropolyacid andparticles of the neutral potassium salt, the sample being in 78.6% amorphous. On aging at room temperature, theheteropolyacid spreads to form a surface layer covering the neutral potassium salt particles K3PW12O40. Heattreatment of KxH3-xPW12O40 salts, where 2 x < 3, from 313 K to higher temperatures induces the transformationof the heteropolyacid-covering K3 core into a well-dispersed, amorphous surface layer. On further heating of theacidic potassium salts, the surface layer decomposes between 855 and 915 K with the formation of a PW8O26-typebronze as a new phase, the K3PW12O40 salt remaining unchanged. The latter starts to decompose at 1093 K, andin the case of all samples, the process is completed at about 1183 K. Rietveld structure refinement, XPS, and 31PNMR measurements of acidic potassium salts indicate that the core of these salts is always formed by the K3PW12O40salt, which is covered by a heteropolyacid. Comparison of lattice parameters of the K3 salt and HPW leads to theconclusion that the layer is composed of partially or completely dehydrated heteropolyacid molecules. The coverageof the core by HPW in the K2 sample was estimated to be equal to one monolayer.