Structural evolution and synthesis mechanism of ytterbium disilicate powders prepared by cocurrent chemical coprecipitation method

Ytterbium disilicate powders were synthesized by cocurrent chemical coprecipitation method. The influence of Si/Yb molar ratio and calcination temperature on compositions and structures of Yb2Si2O7 products were investigated. The formation mechanism and thermal behavior of precursor as well as the phase evolution of Yb2Si2O7 were also discussed in depth. Results show that pure beta-Yb2Si2O7 powders with nanoscale size can be obtained from the precursor with Si/Yb molar ratio of 1.1 after being calcined at temperatures above 1200 degrees C. The Yb2Si2O7 precursor is an amorphous polymer cross-linked with -[Si-O-Yb]-chain segments which are formed though Yb atoms embedding in the -[Si-O-Si]-network. After a continuous dehydroxylation and structural ordering, the amorphous precursor transformed into alpha-Yb2Si2O7 crystals by atomic rearrangement. Elevated calcination temperature can induce to the coordination structures and environment evolutions of structural units and then converted to stable (Si2O7) groups and (YbO6) polyhedrons, which results in the formation of beta-Yb2Si2O7.

Automated summary

Ytterbium disilicate powders were synthesized by coprecipitation method, and the effects of Si/Yb molar ratio and calcination temperature on the compositions and structures of the products were investigated. The formation mechanism and phase evolution of Yb2Si2O7 were discussed, and it was found that the precursor transformed into pure beta-Yb2Si2O7 powders with nanoscale size after calcination at temperatures above 1200 degrees C.