Crystal‐field splittings of gadolinium (4f7) levels in C‐type rare earth oxides

The absorption spectrum of C‐Gd2O3 was recorded at room temperature up to 40 600 cm−1. 47 Stark levels of the 4f7 configuration were obtained. The fluorescence spectra from the 6P7/2 level were recorded for Gd3+ in Y2O3 and Yb2O3. The crystal‐field splittings are large. Because of the peculiarities of the half‐filled shell, the experimental results (32 Stark levels) were fitted with a C2v‐type crystal field Hamiltonian restricted to operators of rank 2 and 4, applied on six different basis sets for J = 3/2, 5/2, 7/2 (two matrices), and 9/2 (two matrices) limited by a truncation choice depending on free‐ion wave vectors and ignoring J mixing. Real crystal field parameters of rank 2 and 4 were obtained for the C2 site of C‐Gd2O3 and are in agreement with those previously determined for Eu3+. The fluorescence data yielded a large value (−1700 cm−1) for the B20 parameter of the S6 site in C‐Y2O3.