A ferroelectric cathode is employed in a cyclotron-resonance maser (CRM). The CRM oscillator device operates at ∼7 GHz, near the cutoff frequency of a hollow cylindrical cavity. The cathode is made of a PLZT 12/65/35 ceramic with high-dielectric constant (εr∼4000). Electrons are extracted from the plasma excited on the cathode surface by ∼1 kV short rise-time pulses. The use of ferroelectric cathodes may advance the microwave tube technology for various applications.