Yttrium Oxide Upconverting Phosphors. Part 2 † :  Temperature Dependent Upconversion Luminescence Properties of Erbium in Yttrium Oxide

Emission bands from Er3+ ions on C2 and S6 sites of cubic Y2O3 have been observed under 632.8 nm excitation. The well-known green hot band in the region of 520−540 nm and a new blue-green hot band in the region of 469−474 nm have been observed from Er3+ on both sites. These hot bands are assigned to the 2H11/2 → 4I15/2 and the 4F3/2 → 4I15/2 transitions, respectively. In addition to observing different thermal behavior for the emissions from Er3+ ions on different lattice sites due to these transitions, different thermal behavior has also been observed for the 4F5/2 → 4I15/2, 4F9/2 → 4I15/2, 4S3/2 → 4I15/2, and 4I11/2 → 4I15/2 transitions. The 4G11/2 → 4I15/2, 2H9/2 → 4I15/2, and 4I9/2 → 4I15/2 transitions gave rise to bands which were too weak for accurate temperature-dependent studies. Emission arising from the 4F7/2 → 4I15/2 transition was observed with 514.5 but not 632.8 nm excitation.