Microstructure and electrical properties of Aurivillius phase (CaBi2Nb2O9)1-x(BaBi2Nb2O9)x solid solution ZhangHongtao YanHaixue ReeceMichael J. 2015 Microstructure and electrical properties of Aurivillius phase (CaBi2Nb2O9)1-x(BaBi2Nb2O9)x solid solution