THE LOCAL-STRUCTURE CHARACTERIZATION AND RESULTING PHASE-TRANSITION MECHANISM OF AMORPHOUS ZRO2

In the framework of Faber-Ziman's formalism, the radial atomic number density distributions rho(r) for two amorphous ZrO2-gel samples have b een derived, and used to perform local structure simulations based on the monoclinic and tetragonal crystal skeletons in order to determine and investigate the local structure of amorphous ZrO2. The results ind icate that the topological structure of amorphous ZrO2 bears more rese mblance to monoclinic ZrO2 structure than to the tetragonal one. Moreo ver, the random structure in the amorphous ZrO2 is characterized mainl y by the first-kind disorder in the short-range. According to this str uctural picture of amorphous ZrO2, a phase-transition mechanism of amo rphous ZrO2 has been proposed, by which the crystallization of amorpho us ZrO2 is considered starting with the formation of monoclinic nuclei followed by their further growth or conversion to the tetragonal phas e, depending on the particular kinetic conditions and chemical environ ments. This proposed mechanism can help in the understanding of some e xperimental results that are not yet well understood.