STUDY OF THE CATALYSTS FOR FUEL COMBUSTION REACTIONS .18. THERMAL-STABILITY OF A LA2O3-MGO-AL2O3 SYSTEM

X-ray diffraction analysis was used to study the aluminum oxide system s modified with magnesium and lanthanum ions. It is shown that stabili zation of magnesium and lanthanum ions in mixed solid solutions occurs at the tetrahedral and octahedral positions, respectively, that subst antially constrains the diffusion of aluminum ions and, consequently, prevents the formation of high-temperature oxide modifications at elev ated temperatures. The thermal stability of alumina is attributed to t he magnesia-lanthana solid solutions formed on the basis of gamma-Al2O 3.