A simple route to full structural analysis of biophosphates and their application to materials discovery

Abstract

An integrated suite of synthesis and characterisation techniques that includes synchrotron-based single crystal, powder X-ray diffraction, nuclear magnetic resonance and electron diffraction have been employed to uncover two new distinct structures in the Ca_xBa_2−xP₂O₇ polymorphic phosphate system. These materials have particular relevance for their application as both biomaterials and phosphors. Calcium barium pyrophosphate, CaBaP₂O₇, was shown by a combination of spectroscopic and diffraction techniques to have two polymorphs distinct in structure from all of the five previously reported polymorphs of Ca, Sr and Ba pyrophosphate. A high temperature polymorph HT-CaBaP₂O₇ prepared at 1200 °C is orthorhombic, of space group P₂₁₂₁₂₁ with a = 13.0494 Å, b = 8.9677 Å, c = 5.5444 Å. A low temperature polymorph LT-CaBaP₂O₇, prepared below 1000 °C, is monoclinic with space group P2₁/c and dimensions a = 12.065 Å, b = 10.582 Å, c = 9.515 Å, β = 94.609°.