Er2O3
Saiki, A.Ishizawa, N.Mizutani, N.Kato, M.
Journal of the Ceramic Association, Japan (1985) 93, 1082 649-654
a=10.566Å b=10.566Å c=10.566Å
α=90° β=90° γ=90°
O3Yb2
a=10.4579Å b=10.4579Å c=10.4579Å