The zone of the ternary system Al2O3-La2O3-Cr2O3 delimited by LaCrO3, LaAlO3, Al2O3 and Cr2O3 has been examined. The existence of an extended field of mixed crystals with rhombohedral symmetry LaAl1-xCrxO3 (0≤x≤0·85) has been verified. On the other hand, for x>0·85, the solids show XR diffraction spectrograms typical of the orthorhombic phase LaCrO3. It has been found a small isomorphous substitution of Al3+ by Cr3+ in the β-alumina type phase, leading to the formation of the LaAl11-x CrxO18 series (0≤x≤0·75); moreover, the existence of Al2-xCrxO3 (0≤x≤2) mixed crystals field has been confirmed. Finally it has been experimentally verified that catalytic systems formed by mechanical mixtures of LaCrO3 and Al2O3 prepared anyhow (LaCrO3 dispersed or supported on Al2O3) result thermodynamically unstable whatever the composition.
|Titolo:||Solid state equilibria in the system Al2O3-La2O3-Cr2O3: Reactivity catalyst/support LaCrO3/Al2O3|
|Data di pubblicazione:||1998|
|Appare nelle tipologie:||1.1 Articolo in rivista|