Probing the interface of core shell particles of GaPO_4 and AlPO_4 by ~(31)P MAS NMR spectroscopy

摘要

Hexagonal GaPO_4, pseudo-hexagonal AlPO_4 and the core shell particles of these phosphates have been prepared in ethylene glycol medium at 180 °C, followed by annealing at 900 °C for 24 h and investigated by powder X-ray diffraction and ~(31)P Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR) techniques. The ~(31)P 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 Al~(3+) and Ga~(3+) as the next nearest neighbors around the probe ~(31)P nuclei of the PO_4 tetrahedron. Existence of different PO_4 structural units with varying number of Al~(3+) and Ga~(3+) 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.