Thermionic electron emission cathodes are critical components of various high
power and high frequency vacuum electronic devices, electron microscopes,
e-beam lithographic devices, and thermionic energy converters, which all demand
an efficient and long-lasting low work function cathode. Single phase,
polycrystalline perovskite oxide SrVO3β, with its intrinsic low effective
work function and facile synthesis process, is a promising cathode candidate,
where previous works have shown evidence of an effective work function as low
as 2.3 eV. However, assessment of the stability over time under conditions
relevant for operation and the related interplay of evolving surface chemistry
with emission performance are still missing, and necessary for understanding
how to best prepare, process and operate SrVO3β cathodes. In this work, we
study the vacuum activation process of SrVO3β and find it has promising
emission stability over 15 days of continuous high temperature operation. We
find that SrVO3β shows surface Sr and O segregation during operation, which
we hypothesize is needed to create a positive surface dipole, leading to low
effective work function. Emission repeatability from cyclic heating and cooling
suggests the promising stability of the low effective work function surface,
and additional observations of drift-free emission during one hour of
continuous emission testing at high temperature further demonstrates its
excellent performance stability