1. CEMDRX, Department of Physics, University of Coimbra, Rua Larga, 3004-516 Coimbra, Portugal
2. Department of Materials and Ceramic Engineering, Centre for Research in Ceramics and Composite Materials, CICECO, University of Aveiro, 3810-193 Aveiro, Portugal
3. Department of Materials Science and Engineering, University of Sheffield, Sir Robert Hadfield Building, Mappin Street, Sheffield, S1 3JD, U.K.