4 in field-emission display (FED) devices have been constructed and analyzed utilizing Spinelt-type cathodes, uniquely developed low-voltage phosphors and spacers. The cathode was especially fabricated without using a resistive layer. The reliability and the feasibility of the FED device have been tested both in a vacuum chamber and in a fully sealed condition. The electrical aging effect on microtip emission properties were carried out, which resulted in significant enhancement in electrical characteristics of the FED device. The fully sealed FED device was analyzed as a function of lifetime. Additionally, the characteristics of the phosphor and the spacer used in our FED device are discussed.