1. a Institute of Materials in Electrical Engineering II , University of Aachen , Sommerfeldstr 24, Aachen , 52074 , Germany
2. b Institute of Materials in Electrical Engineering I , University of Aachen , Sommerfeldstr 24, Aachen , 52074 , Germany
3. c Department IFF, Research Center Juelich , Institute of Electroceramic Materials (EKM) , Juelich , 52425 , Germany