Phase Relations in the LiOH–ZrO2–GeO2–H2O System at 500°C and 0.1 GPa

The phases crystallizing in the LiOH–ZrO2–GeO2–H2O system at 500°C and 0.1 GPa are Zr[8]Ge[4]O4 , Li2Ge[6]Ge2[4]O6(OH)2, Li3HGe4[6]Ge3[4]O16 · 4H2O, and Li2Ge[4]O3. These phases differ in the oxygen coordination of Ge. At a ZrO2 : GeO2 molar ratio of 1 : 1, increasing the LiOH concentration leads to the crystallization of a ZrO2 + Li2GeO3 mixture, instead of ZrGeO4 . At ZrO2 : GeO2 ratios in the range 1 : 2 to 1 : 6, Li2Ge[6]Ge2[4]O6(OH)2 crystallizes together with ZrGeO4 . The formation of the structures of ZrGeO4 and Li2Ge[6]Ge2[4]O6(OH)2 is discussed in terms of the matrix assembly of crystal structures from cyclic subpolyhedral structural units.