Anomalous Crystallization of Some Alloys in Refractory Oxide Systems Based on Zirconia, Yttria and Erbia

Peculiarities of crystallization of alumina, yttria and rare-earth element oxides of yttria subgroup in an optical furnace

“…32,33 These results contradict those obtained by the levitation method. 10,15 The method for the estimation of volume change upon crystallization under the conditions of a center-symmetrical temperature field in the focal zone of an optical furnace has been proposed.…”

“…10,15 The method for the estimation of volume change upon crystallization under the conditions of a center-symmetrical temperature field in the focal zone of an optical furnace has been proposed. [32][33][34] It has significant limitations and cannot be used for substances with high melt viscosity, disposed to the formation of internal hollow spaces, to which Al 2 O 3 is related. Nevertheless, the second task was to thoroughly research the solidification process of alumina in the focal zone of an optical furnace, and comparing the peculiarities of the alumina crystallization with the crystallization processes in REE oxides under the same conditions, and to estimate the influence of their peculiarities on the reliability of the reported results.…”

“…Nevertheless, the second task was to thoroughly research the solidification process of alumina in the focal zone of an optical furnace, and comparing the peculiarities of the alumina crystallization with the crystallization processes in REE oxides under the same conditions, and to estimate the influence of their peculiarities on the reliability of the reported results. 32,33 In addition, crystallization of alumina and REE oxides under the above-mentioned conditions and at different cooling rates is characterized by other peculiarities. The third task of the present work was to consider them as well.…”

Method for evaluating the change in specific volume of refratory substances during crystallization

“…In the stepwise model crystallization was broken down into stages, and it was assumed that the relative change in molten bath radius during each crystallization stage equalled the relative change in molten bath depth [4]. With calculation by the radial model [3] crystallization close to the bottom of the molten bath was ignored, and the radial change in molten bath was considered exclusively.…”

“…In carrying out crystallization of a flat bath of melt a shrinkage cone forms (in rare cases it is projecting) in the direction of the boundary of the molten bath towards the center at the surface of an ingot. The dimensions and shape of the cone are commensurate with the volume of the molten bath and the volume of the crystallized phase specify the change in specific volume of the substance during crystallization [3,4].…”