English

DTIC ADA192357: Thermochemistry of Dispenser Cathode Impregnant Materials: Phase Equilibria in the BaO-CaO-Al2O3 System

The goal of this study was to establish the subsolidus and liquid- solid equilibrium relationships in the high-baria portion of the barium calcium aluminate system. The solidus and liquidus temperatures were determined for forty different compositions. From these data, the liquidus and solidus surfaces were characterized and presented in the form of a ternary diagram. Four vertical (isoplethic) sections were also constructed which describe the crystallization sequences along non-binary planes in the system. Two isothermal sections were constructed describing the subsolidus equilibria in the high-baria corner at 1100 deg C and 1475 deg C. The solubility of calcium in the crystal structures of Ba4A1207 and Ba3A1206 was 20.5 and 18.8 mole percent respectively and was found to be independent of temperature over the range 1100 deg C to 1475 deg C. Keywords: Phase equilibria, Barium calcium aluminate system, Subsolidus, Phase diagram.

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