Effect of Sc2O3 addition on the phase composition and electron emission performance of Co-precipitated aluminates for impregnated cathodes.

Herein, a series of 6BaO·1CaO·2Al 2 O 3 + x wt% Sc 2 O 3 (x = 1, 3, 5, 7, 9) impregnants were synthesized by a liquid-phase co-precipitation method and subsequent sintering at 1200 °C. The as-synthesized emissive materials were impregnated into porous tungsten matrices at 1700 °C, and their phase composition and electron emission performance were investigated. The X-ray diffraction analysis of the sintered and melted impregnated products revealed that they comprised multi-phase structures consisting of (Ba,Ca) 3 Al 2 O 6 , Ba 2 ScAlO 5 , and BaAl 2 O 4 phases. Furthermore, the addition of 3 wt% Sc 2 O 3 to the impregnated test cathodes significantly increased the emission level of the test cathode to 11.4 ± 0.6 A cm−2 at 1100 °C B (i.e., brightness temperature). The relationship between the electron emission properties and phase concentration in the impregnants was analyzed, and the results revealed that the emission performance of the cathodes deteriorated with an increase in the Sc 2 O 3 content, which could be attributed to an increase in the concentration of non-active BaAl 2 O 4 phase in the impregnants. [ABSTRACT FROM AUTHOR]