125Te NMR Probes of Tellurium Oxide Crystals: Shielding-Structure Correlations.

The local environments around tellurium atoms in a series of tellurium oxide crystals were probed by 125Te solid-state NMR spectroscopy. Crystals with distinct TeOn units (n from 3 to 6), including Na2TeO3, α-TeO2 and γ-TeO2, Te2O(PO4)2, K3LaTe2O9, BaZnTe2O7, and CsYTe3O8 were studied. The latter four were synthesized through a solid-state process. X-ray diffraction was used to confirm the successful syntheses. The 125Te chemical shift was found to exhibit a strong linear correlation with the Te coordination number. The 125Te chemical-shift components (δ11, δ22, and δ33) of the TeO4 units were further correlated to the O-Te-O-bond angles. With the aid of 125Te NMR, it is likely that these relations can be used to estimate the coordination states of Te atoms in unknown Te crystals and glasses.