焦绿石型氧化钨是一种具有广泛潜在用途的新兴材料.研究从钨酸铵-碳酸铵溶液中水热制备焦绿石型氧化钨过程中铁的价态和亚铁离子添加量对钨结晶率的影响,重点研究亚铁离子促进钨结晶过程的机理.结果表明,亚铁离子能显著促进钨的结晶过程,而单质铁和三价铁离子的影响甚微;钨结晶率随亚铁离子添加量的增加而升高,当亚铁离子浓度为16 g/L时,钨结晶率达到最大值～60％.结晶母液的红外光谱(FTIR)分析表明,亚铁离子能促进溶液中WO4四面体向WO6八面体转变;结合结晶产物的X射线光电子能谱(XPS)和X射线衍射(XRD)分析,亚铁离子对钨结晶的促进作用可归因于亚铁离子嵌入焦绿石型氧化钨晶格而导致其面间距的增加.研究结果有助于焦绿石型氧化钨粉体的高效制备和钨的清洁生产.%Pyrochlore-type tungsten oxide (PTO), WO3·0.5H2O, is an emerging material with very wide potential applications. The influences of iron valences and the additive amount of ferrous ion on tungsten crystallization ratio and the acceleration mechanism of ferrous ion were investigated when PTO was hydrothermally prepared in aqueous ammonium tungstate solution containing ammonium carbonate. The results show that ferrous ion can remarkably accelerate tungsten crystallization while both elemental iron and ferric ion have little influence on the crystallization. Moreover, the tungsten crystallization ratio increases with increasing the amount of ferrous ions added and reaches the maximum of about 60％ with ferrous ion concentration of 16 g/L. FTIR analysis of the spent solution after PTO crystallization shows that ferrous ion can accelerate the conversion of WO4 tetrahedral to WO6 octahedron. Combined with XPS and XRD analyses of the hydrothermal product, the acceleration effect of ferrous ion on tungsten crystallization could basically be attributed to the increase in the interplanar spacing of PTO lattice caused by the incorporation of ferrous ion into PTO crystal lattice. The results presented is conducive to the efficient preparation of PTO powder and cleaner tungsten metallurgy.
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