1. Fraunhofer Institute for Silicate Research ISC Neunerplatz 2 97082 Würzburg Germany
2. Julius‐Maximilians‐Universität Würzburg Chemical Technology of Material Synthesis Röntgenring 11 97070 Würzburg Germany
3. Leiden University LION Leiden Institute of Physics Niels Bohrweg 2 Leiden 2333 CA The Netherlands