The present disclosure is directed to a method of converting green particles to form finished particles. The apparatus used for sintering incorporates an elongated hollow tube (12), an insulative sleeve there about to define an elevated temperature zone, and a microwave generator (22) coupled through a wave guide into a microwave cavity incorporated the tube. The particles are moved through the tube at a controlled rate to assure adequate exposure to the microwave radiation. A second embodiment sinters a solid part in a cavity or mold.