Nachweis der verschiedenen Phasen und Phasenübergänge des Systems Fe-Ga im Konzentrationsbereich 25,7 bis 28,3 At-% Ga bei Temperaturen von 20 °C bis 720 °C mit Hilfe des Mössbauer- Effekts

Abstract

Abstract Fe-Ga-absorbers, bcc-unordered at 20 °C, with 25.7, 27.0, and 28.3 at-% Ga were analyzed up to 720 °C with the Mössbauer effect in order to clear disagreements of former experiments of us with the then known phase diagrams. We found proofs for an ordering transition A2 -DO3 between 180 and 260 °C, a transition DO3 -Ll2 between 280 and 380 °C, a transition Ll2 -DO19 in a small temperature interval at 610 °C, and a further one DO19 - DO3 (or DO19-B2) at 630 °C. The temperature dependence of the magnetically induced Ll2-field gradient q was analyzed. Probably q is negative, while the direction of the magnetic field is parallel [1, 0, 0] in agreement with other experiments at low temperatures. Above 630 °C there seems to exist a further so far unknown ordered phase, which is probably non-cubic with at least two different Fe-sites. Our results are in considerable agreement with recently published phase diagrams, though some of our spectra allow different interpretations.