Electron emission from Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ ferroelectric cathode

(1-x)Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ materials near the morphotropic phase boundary are selected for tentative electron emission experiments due to their excellent piezoelectric and ferroelectric properties and relatively high dielectric constants. The influences of ferroelectric and dielectric properties of ferroelectric cathode material on its threshold voltage are studied. The relationship between emission current and triggering voltage is investigated, and the relationship between emission current and extracting voltage is studied as well. The electron emission mechanism is also analyzed. The results show that emission threshold voltage of the relaxation ferroelectric 0.9Pb(Mg_1/3Nb_2/3)O₃-0.1PbTiO₃ is smaller due to its high dielectric constant at room temperature and large polarization variation. Low threshold voltage means low power consumption. This is an important factor to be considered in actual application for ferroelectric cathode and it has an important reference value. Electron emission is associated with fast polarization reversal and the formation of the plasma. The self-emission current starts on the falling edge of the triggering voltage pulse, which means that it is caused by polarization reversal. The amplitude of the self-emission current grows exponentially with the increase of triggering voltage. The amplitude of emission current shows a linear growth with the increase of extracting voltage when it is larger. It indicates that large current is determined mainly by extracting voltage. Larger current needs larger extracting voltage. The emission current starts on the rising edge of the triggering voltage pulse. It is associated with the field enhancement effect near "three interface points" and the formation of the plasma. An emission current of 210 A is obtained from the ferroelectric cathode under an extracting voltage of 2500 V, and the corresponding current density is 447 A/cm².