Synthesis of Bismuth Germanate with a Crystalline Eulithine Structure by Casting

The conditions for the preparation of a compound with an eulithine crystal structure (ECS) during the crystallization of a stoichiometric melt in the Bi 2 O 3 –GeO 2 system by casting have been investigated. The initial components (Bi 2 O 3 and GeO 2 ) were placed in a platinum crucible and heated to a temperature in zone C at a rate of ~20°C/min, with holding under isothermal conditions for 1 h. Then, the melt was poured from the crucible onto a heated platinum plate. The macrostructure of the surface of the crystallized samples was observed using a Stemi 2000 stereoscope (Carl Zeiss), and the microstructure was observed using a Carl Zeiss Axio Observer A1m optical microscope on microsections. X-ray phase analysis (XRD) of the powder was performed on a Shimadzu XRD 6000 diffractometer (Cu K α radiation). Atomic absorption spectrometry was carried out on a SOLAAR M device. For the first time, the possibility of obtaining Bi 4 Ge 3 O 12 with the eulithine crystal structure (ECS) by fusing a stoichiometric mixture of initial oxides and subsequent cooling of the melt by casting was experimentally shown. It is shown that, when using this method, it is possible not only to achieve record rates of synthesis but also to reduce the content of platinum (which is a harmful impurity) in the resulting material by 2 times.