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

The peculiarities crystallization of alumina, yttria and the rare-earth element oxides of the yttria subgroup in an optical furnace have been studied. Direct evidence of oxygen dissolution during alumina melting in oxidizing atmosphere and its ejection during crystallization has been presented. The released oxygen was captured by the inside hollows of alumina ingots, and its quantity was controlled using gas chromatography. It was not less than 8 × 10−6 g in 1 g of alumina. The quantity of the oxygen released is corresponding to that for REE oxides. The yttria specific volume increasing during crystallization was confirmed. The apparent ingot volume of Er, Ho, Tm, and Yb oxides does not change, while the specific volume of lutecia decreases.