The operation of a planar diode with a large area (64 cm2) ferroelectric plasma cathode based on BaTiO3 ceramics is studied. Diode parameters and parameters of the generated electron beam are investigated under accelerating voltage of 200–350 kV and pulse duration of 250 ns. Parameters of the plasma, which forms on the surface of the ferroelectric cathode due to incomplete discharge, are reported as well. It is shown that the application of this cathode allows one to produce an electron beam simultaneously with application of the accelerating pulse. The generation of an electron beam with current density up to 20 A/cm2 and divergence of less than 1° is demonstrated. It is shown that diode operation is governed by parameters of the cathode plasma which fills the anode–cathode gap prior to application of the accelerating voltage pulse. By proper adjustment of the cathode and diode parameters the operation of the diode with almost constant impedance is achieved. Measurements of the potential distribution in the diode confirm that the diode operates in a plasma-prefilled mode. The cathode is found to be capable of operating for up to 105 pulses at a repetition rate of few Hz without any maintenance and with relatively small vacuum deterioration. © 2001 American Institute of Physics.