HYDROTHERMAL GROWTH OF CRYSTALS OF LaAlO3
Semiannual technical summary rept. for 31 Dec 1964-1 Jul 1965
LITTON SYSTEMS INC MORRIS PLAINS NJ AIRTRON DIV
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Large crystals of LaAlO3 were successfully grown from a straight PbF2 flux. However, soak temperatures above 1400C are required for solution of LaF3 formed by the reaction of La2O3 and PbF2. These high temperatures result in premature failure of the furnace and platinum container. PbF2 was, therefore, abondoned and a search was initiated to modify the PbF2 flux, or to find a more suitable solvent. Among the solvents investigated were PbO-PbF2, BaO and Bi2O3, all with small additions of B2O3. Results are encouraging. The regions of phase stability were determined for LaAlO3 and LaOH3 under hydrothermal conditions. From this data it is apparent that in order to operate in a region where LaAlO3 is the only stable solid and to stay below the 435C transition temperature, the solvent concentrations must be 2 or 7 m K2CO3. The composition of the fluid was analyzed quantitatively for alumina and lanthana content. Although the data show considerable scatter, they are in agreement with and have confirmed the observed crystallization of solid LaOH3. In the large crystal growth autoclaves, spontaneous nucleation of LaAlO3 in the growth chamber has been obtained from a nutrient composed of powdered La2O3 and flame fusion ruby pieces.