Probing the interface of core shell particles of GaPO4 and AlPO4 by 31P MAS NMR spectroscopy

Hexagonal GaPO4, pseudo-hexagonal AlPO4 and the core shell particles of these phosphates have been prepared in ethylene glycol medium at 180 degrees C, followed by annealing at 900 degrees C for 24 h and investigated by powder X-ray diffraction and P-31 Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR) techniques. The P-31 NMR studies of these core shell particles showed a multi-component NMR pattern consisting of five peaks originating due to the distinct structural configurations formed by the varying number of Al3+ and Ga3+ as the next nearest neighbors around the probe P-31 nuclei of the PO4 tetrahedron. Existence of different PO4 structural units with varying number of Al3+ and Ga3+ as its next nearest neighbors around P nucleus at the interface of the core shell particles has been confirmed. These results clearly indicate the bond formation at the interface between the core and shell material for these particles. (C) 2010 Elsevier Masson SAS. All rights reserved.