Dawson结构多金属含氧酸盐热解性质研究

用变温XRD,变温IR以及TG-DTA等方法,系统地研究了具有Dawson结构的Ym Hn P2 M12 O62·qH2O(Y=K+,NH4+,Cu2+;M=Mo,W)的热解性质,获得了它们较为精确的热分解温度,对其热分解的判断方法提出了一些新的见解.结果表明,以钼为配位原子的Dawson结构钾盐,铵盐,铜盐分别在250℃,210℃,240℃发生了热重排,生成了具有Keggin结构的化合物.以钨为配位原子的钾盐在410℃也有相似的行为,但铵盐和铜盐却没有观察到类似的热重排现象,分别在400℃,450℃直接热分解为WO3.这些结果显示,热重排现象的发生可能与相应的Keggin结构化合物的热稳定性有关.

Thermal decomposition behavior of metal-oxygen clusters with Dawson structure

The thermal decomposition behavior of metal-oxygen clusters with Dawson structure,Ym Hn P2 M18 O62?qH2O, was systematically investigated using the X-ray power thermodiffractometry and FTIR at different temperatures, TG-DTA. The experimental results indicated that Dawson-typ emetal-oxygen clusters with anion, P2 Mo18 O62]6- , and different counter cations, NH4+, Cu2+, K+, un-derwent an irreversible thermal rearrangement around 210℃,240℃,250℃, respectively to give the corresponding Keggin-type metal-oxygen clusters containingPMo12O40]3- as one of the prod-ucts. For the metal-oxygen clusters containing tungsten, the pyrolysis procedure of potassium salt with P2 W18 O62]6- anion is similar to that of metal-oxygen dusters with P2 Mo18 O62]-6 an-ion, whenas the NH4+, Cu2+ salts of P2 W18O62]6- seem to decompose directly into WO3 at 400℃, 450℃, respectively. These results testify that the thermal solid-state rearrangements of Dawson-type anions correlated with the thermal stability of the corresponding Keggin-type com-pounds. Furthermore, some proposals about the criterion and the adjudication of thermal decom-position temperature for metal-oxygen clusters with different thermal decomposition behavior are also given.