Low Temperature Synthesis of Metal Oxide Bronze Phases and their Electric Properties

（一）.我们发现，在低温（500 ℃）下由过氧多钨酸钾合成的钾六方钨青铜（K-HTB）在室温潮湿气氛中电阻率显著增加。通过重量分析、复阻抗谱和粉末XRD测量研究了水的掺入增加介电常数的机理。粉末XRD分析表明，超晶格结构的K-HTB出现通过掺入水。根据这些结果提出了K-HTB的层状结构模型。（二）、通过溴化钡与过氧聚硅酸溶液反应，沉淀出无定形盐。将其在氢气流中在接近550 ° C的温度下加热，产生了纯相的六方钡钨青铜Ba_xWO_3，x在0.19-0.24之间。在高于620 ℃的温度下，该亚稳化合物转变为四元青铜相。以同样的方法在较低的温度（420 ℃）下合成了一种未见报道的六方结构的铅钨青铜（Pb_WO_3的a=7.408，c=3.786<0.29>）。用Rietveld方法对它们的晶体结构进行了优化。在4.2K ~室温范围内研究了化合物的电学性质。

(1). We have found that potassium hexagonal tungsten bronze (K-HTB) synthesized from potassium peroxo-polytungstate at low temperature (500ﾟC) shows a remarkable increase in resistivity in a humidid atmosphere at room temperature. The mechanism of the resistivith increase by incorporation of water was investigated by gravimetry, complex impedance spectroscopy, and powder XRD measurement. The powder XRD profiles indicated that superlattice structure of the K-HTB emerges by incorporation of water. A layr structure model of the K-HTB was suggested from these results.(2). An amorphous salt was precipitated by reacting barium bromide with a solution of peroxo-polytangstic acidl. Heating it in a hydrogen stream at temperature near 550ﾟC yielded a hexagonal form of barium tungsten bronze, Ba_xWO_3, in a pure aphase with x being in the range 0.19-0.24. At temperature higher than 620ﾟC,this metastable compound was transformed into the tetragonal bronze phase. An unreported lead tungsten bronze in the hexagonal form (a=7.408, c=3.786 A,for Pb_<0.29>WO_3) was synthesized similarly but at lower temperature (420ﾟC). Their crystal structures were refined by the Rietveld method. The electric properties of the compounds were also investigated between 4.2K to room temperature..