Neutron diffraction study on glass-ceramics

Neutron diffraction and Rietveld full-pattern-fitting methods were applied to investigate the evolution of microstructure and internal stress of glass-ceramics under slow cooling and rapid cooling. Comparing to slow cooling, rapid cooling results in further elongation of the three axes for the unit cell of precipitated β-wollastonite crystal,and larger tensile stress from the residual glass phase, but smaller atomic displacive disorder. Excessive local stress results in the ermergence of micro crack in the area where stress centralizes. The intensity of amorphous peaks at high diffraction angles for the rapid cooling sample is much higher than that of the slow cooling sample, showing that the percentage of the residual glass phase in the rapid cooling sample is higher than that in the slow cooling sample. The strain value measured by neutron diffraction is very different from that of X-ray difffraction, showing that the internal stress differs significantly from the stress existing at the surface. Neutron diffraction is a practical method for determination of average residual strain in bulk glass-ceramics and for investigation of its complex microstructure where crystalline phase and glass phase coexist. (authors)