ABSTRACT
This chapter focuses on the luminescence from complex ions with closed-shell electronic structures such as the scheelite compounds and others and describe a variety of applications for these phosphors. It discusses Other interesting luminescence centers such as uranyl(II), platinum(II), mixed-valence, and other complexes. Yttrium vanadate (YVO4) is a very useful phosphor in use for a long time. This compound does not show luminescence at room temperature; but at temperatures below 200K, it shows blue emission centered at 420 nm. The degree of polarization in luminescence has been measured in some molybdate single crystals as a function of temperatures in the low-temperature region. Orange-to-red luminescence is also observed in some molybdate complexes in addition to the green luminescence. Jorgensen and Reisfeld have thoroughly discussed the historical background and theoretical aspects of the luminescence of these centers. The electronic structure of uranyl ions is particularly interesting.
