Novel microstructures of self-assembled microcrystallites of (NH4)(3)PW12O40 and Cs3PW12O40

Three different microstructures of self-assembled microcrystallites (or of aggregates) of heteropoly compounds, (NH4)(3)PW12O40 and Cs3PW12O40 have been found: (1) microcrystallites that self-assembled with unidirectional orientation and were epitaxially connected with each other to form dodecahedra, (2) microcrystallites that self-assembled with unidirectional orientation, but were little connected epitaxially each other to form round aggregates, and (3) dispersed fine particles. This variation of the microstructure was consistently explained by the change in the solubility of the compounds, that is, the precipitation temperature and the kind of cation.