Research and development of relaxor ferroelectric ceramics at NEC

The authors describe the development of many systems containing relaxor ferroelectrics studied for multilayer ceramic capacitors at NEC Corporation since 1975. These ceramics were composed of complex perovskite compound containing lead ion and were categorized into three types. The complex perovskite systems containing Pb ions and W ions were suitable for a low firing temperature and showed a high dielectric constant with a smaller grain size than a BaTiO₃ system. Multilayer capacitors with large capacitance have been manufactured from these systems. Pyrochlore compound was effective for suppression of grain growth and resulted in bend strength increases, The use of alkoxide powder was very promising. The multilayer ceramic capacitors made from this powder showed a very high capacitance per volume