Add time:07/19/2019         Source:sciencedirect.com

The effects of air, hydrogen, and CO2 and O2 mixture sintering atmospheres on the structure, micromorphology, electron emission capability and environmental stability of 612 type barium-calcium-aluminates have been investigated. Both the 6BaO-1CaO-2Al2O3 aluminates sintered in air and hydrogen crystallize in the Ba3CaAl2O7 phase. However, the aluminates with the same composition sintered in CO2 and O2 mixture crystallizes in the Ba3Al2O6 phase with a small amount of BaCO3 reactant. The microstructure for the aluminates sintered in air and H2 show similar features while the sample sintered in CO2 and O2 mixture atmosphere shows better conglomeration. Emissivity tests indicate that the divergent current density Jdiv for the dispenser cathodes impregnated with aluminates sintering in air, H2, and CO2 and O2 mixture atmospheres are 6.0, 6.1, and 7.6 A cm−2 at 1130 °CB, respectively. Finally, environmental stability tests indicate that the aluminates with the Ba3CaAl2O6 phase sintered in air as well as hydrogen is more environmentally stable than that with Ba3Al2O6 phase sintered in CO2 and O2 mixture. The process of sintering 612 aluminate in CO2 and O2 mixture is beneficial for superior emissivity on the condition of avoiding exposure to moisture.

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