Revealing The Structures In Short- And Middle-Order Of Lanthanum-Doped Al2o3-Napo3 Glasses By Solid State Nmr Spectroscopy

Glasses in the xLa(2)O(3)-yAl(2)O(3)-(100 - x - y)NaPO3 system were synthesized by a melt quenching method, where 0 <= x <= 7.5, y = 0 and x = 5, 5 <= y <= 15. The structures were characterized by advanced multinuclei solid-state nuclear magnetic resonance spectroscopy (SSNMR) and X-ray photoelectron spectroscopy (XPS). P-31 MAS NMR spectroscopy indicates that the glass Q(2) structure is depolymerized by La2O3 and Al2O3, forming multiple Q(xAl)(n) and Q(yLa)(n) phosphorus species, where n, x, and y represent the number of P-O-P, P-O-Al, and P-O-La bonds, respectively. The various phosphorus species were identified by the J-coupling effect based one and two-dimensional (1D and 2D) experiments such as 2D J-resolved, 1D refocused INADEQUATE and 1D P-31{Al-27} J-coupling heteronuclear multiple quantum coherence (HMQC). La is used as a mimic to simulate the local structure of the luminescent rare earth ions. La-139 wideband uniform rate smooth truncation quadrupolar Carr-Purcell-Meiboom-Gill (WURST-QCPMG) spectra show that the coordination number of La is dominantly nine, and some La atoms transfer to lower coordination with the addition of Al2O3. La, Al, and Na atoms exclusively bond to phosphorus tetrahedron PO4, which is evidenced by the P-31/Na-23, P-31/Al-27 double resonance NMR, XPS, and the calculation of charge balance. However, the Al/P and La/P connection methods are much different based on the calculation of charge balance and bond number. Finally, comprehensive and novel local structure models are developed for these rare earth-doped aluminum phosphate glasses.