Thermionic emission of alkali ions from matrices composed of sintered mixtures of aluminosilicate and metal powders are studied. Results show that the emission characteristics depend on temperature, effective work function and voltage in a similar way as does electron emission. The effective work function for these composite emitters varies between 1.1 and 3.4 eV. Short‐term continuous emission densities up to 4.5 mA/cm2have been obtained.