1. Department of SciTec; University of Applied Sciences Jena; Jena 07745 Germany
2. Dept. Electrical Engineering & Information Technology; Ilmenau University of Technology; Ilmenau 98693 Germany
3. Universidad Complutense de Madrid; Facultad de Ciencias Físicas; GFMC Madrid 28040 Spain
4. Fraunhofer Institute of Ceramic Technologies and Systems; Hermsdorf 07629 Germany