1. Haayman P.W., Dam R.W. and Klasens H.A., Method of preparation of semiconducting materials. German Patent 9/350; 1955.
2. Method of preparation of semiconducting materials;Heywang;J. Am. Ceram. Soc.,1964
3. Electrical conductivity at high temperatures of donor-doped barium titanate ceramics;Daniels;Philips Res. Rep.,1976
4. Interfacial segregation in perovskites: microstucture and electrical properties;Desu;J. Am. Ceram. Soc.,1990
5. The positive temperature coefficient of resistivity effect in KNbO3 based ceramics;Tie-zhu;Adv. Mater. Res.,2012