A new strontium borophosphate, Sr6BP5O20, from synchrotron powder data

Strontium borophosphate, Sr6BP5O20, was prepared by a solution synthesis method. The crystal structure was solved ab initio from synchrotron powder data without preliminary knowledge of the chemical formula. The compound crystallizes in space group -4c2. Sr atoms occupy sites coordinated by eight or nine O atoms, and the anionic layer consists of BO4 and PO4 tetrahedra. The eightfold-coordinated Sr atom lies at a site with twofold symmetry, while one P atom and the B atom are located on special positions of site symmetry -4.