Temperature-dependent luminescence of cerium-doped ytterbium oxyorthosilicate

We have measured optical absorption and radioluminescence of Yb1.999Ce0.001SiO5 (YbSO) and found it to be a very poor phosphor. This is in striking contrast to Lu-, Y-, and Gd-based oxyorthosilicates, which are characterized by very strong Ce3+ emission. The absence of luminescence in YbSO is due to quenching of the Ce3+ emission via an [Yb2+-Ce4+] charge-transfer mechanism. Extremely weak band emission observed in YbSO is attributed to transitions connecting the (Yb2+-h(+)) charge-transfer state to the two levels of the Yb2+ 4f(13) configuration. Optical absorption shows the usual bands due to Ce3+ absorption with a band edge near 260 nm. The RL emission spectrum consists of a well-resolved band near 500 nm and an additional band in the region 260-300 nm. The exact position of the latter band cannot be determined due to concomitant Ce3+ absorption. At room temperature the YbSO RL emission is ca. six orders of magnitude weaker than Lu2SiO5 : Ce (LSO) emission. Maximum intensity in the interval 8-300 K occurs near 40 K and is ca. four orders of magnitude weaker than LSO emission. The YbSO band emission is thermally quenched with increasing temperature (40-300 K), consistent with classical theory predictions. (C) 1998 Elsevier Science B.V. All rights reserved.