A Multi-nuclear Multiple-Field Nuclear Magnetic Resonance Study of the Y2O3−Al2O3 Phase Diagram

We have been investigating several compounds belonging to the Y2O3−Al2O3 phase diagram by means of aluminum-27, oxygen-17, and yttrium-89 high-resolution solid-state nuclear magnetic resonance (NMR) spectroscopy. All aluminum, oxygen and yttrium sites of the five crystalline compounds C-Y2O3, Y4Al2O9, YAlO3, Y3Al5O12, and α-Al2O3) have been resolved and the NMR parameters deduced. AlVI sites exhibit isotropic chemical shift δiso between 0 and 10 ppm and small quadrupolar coupling constant CQ, whereas AlIV are located between 70 and 80 ppm and show large CQ. 17O resonances are characterized by small CQ and δiso ranging from 72 ppm (Al2O3) to 358 ppm (Y2O3) and showing a strong sensitivity to the nature of the second coordination sphere of oxygen as well as its coordination number. 89Y δiso are found between 184 and 314 ppm and are not strongly correlated to the coordination state of yttrium, the chemical shift anisotropy being found moderate (∼100 ppm). On the basis of the results obtained with the crystal...