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Changes in the domain structure of anorthites induced by heating

1973; E. Schweizerbart; Volume: 1973; Issue: 1 Linguagem: Inglês

10.1127/njmm/1973/1973/17

2700-2020

Wolfgang Friedrich Müller, H. R. Wenk,

Aerogels and thermal insulation

The effects of he at-treatment on domains in natural anorthites was studied by means of high voltage (650 kV) transmission electron microscopy.No significant change in texture and diffraction contrast of the c-domains was observed in anorthite (An 94.5) heated at 500 and 600° C for 7 days and then quenched or slowly cooled down, but c-domains could not be observed in samples heated at 1200° C for 7 days or at 1430° C for 1 12 hour and subsequently quenched .Heating of anorthite specimens (An 97 and An 100) inside of the electron microscope with a hot stage up to about 575° C showed that the diffraction contrast of the c-antiphase domain boundaries disappears at temperatures above 200-250° C. It reappears, however, after cooling and there is no chan ge in position, shape and size of the antiphase domain boundaries.These observations strongly suggest that the antiphase domain structure as ob~erved at room temperature is not affected by the processes at 200-250° C but controlled by the pattern of structural disorder formed at much higher temperatures.Electron irradiation of heated anorthite caused structural disorder.