Synthesis of sodium and potassium aluminogermanate inorganic polymers

摘要

Synthesis of aluminogermanate inorganic polymers containing sodium as the charge-balancing ion was attempted by reacting NaA10_2 solution with GeO_2 in an adaption of a sol-gel synthesis for aluminosilicate inorganic polymers. XRD and~27A1 MAS NMR suggested that only a small degree of reaction had occurred, based on the presence of unreacted GeO_2 and a trace of Na_3HGe_7O_16-4H_2O, with only a small amount of the tetrahedral aluminium characteristic of a true inorganic polymer. The addition of KOH markedly enhanced the reaction, producing a (Na,K) product with properties characteristic of a true inorganic polymer (an amorphous X-ray powder pattern and predominantly tetrahedral aluminium). An attempt to synthesise the potassium end-member aluminogermanate compound by replacement of the NaA102 in the above synthesis with KA1O_2 produced only crystalline K(AlGeO_4)H_2O and K_3HGe_7O_16-4H_2O containing solely tetrahedral aluminium. Attempts to extend these syntheses to the gallium analogues of these aluminogermanate compounds were unsuccessful, producing only the crystalline products K(GaGeO_4)_6-7H_2O and K_3HGe_7Oi_6-4H_2O. Thus, the most successful sol-gel synthesis of a germanate compound with the properties of an inorganic polymer was of an aluminogermanate containing Na~+ and K~+ as the exchangeable cations.