P-31 MAS and 2D exchange NMR of crystalline silicon phosphates

P-31 MAS NMR has been used to determine P-31 chemical shift tensors of crystalline silicon phosphates. The chemical shift data of five polymorphs of SiP2O7 (hexagonal, tetragonal, cubic and two monoclinic forms) are presented besides those of Si-3(PO4)(4). Results of P-31 2D exchange NMR on a phase mixture of different silicon diphosphates are shown. This novel approach allows an unambiguous identification of the various phases even in multicomponent mixtures as occurring in ceramics.