High‐efficiency secondary electron emission due to incident ions was obtained from a porous MgO‐Ag layer prepared from a suspension of MgO, MgCO3powder, and Ag paste. Field‐dependent secondary emission yield larger than unity was achieved under relatively low‐energy ion bombardment. The introduction of Ag produces a uniform surface potential and therefore results in a stable secondary emission current. This type of emitter is potentially useful for application in gas‐discharge devices.