“…Hidalgo (Hidalgo, Mendez et al 1998) and Muller (Muller, Zhou et al 2009) studied that partially occupied d-shells of these elements play important role in the luminescence and spectroscopy of these elements. Thurbide (Thurbide and Aue 2002), Gedam (Gedam, Dhoble et al 2007), Grinberg (Grinberg, Barzowska et al 2001) and Lapraz (Lapraz, Iacconi et al 1991) reported that in many host materials, these partially occupied d-shells give rise to several important technological applications and in particular, production of high resistivity materials and photonic devices through transition-metal doping has been widely used. Maqbool (Maqbool, Wilson et al 2010) and Martin (Martin, Spalding et al 2001) showed that thermal activation, the oxygen effect and co-dopants are good tools to obtain high efficiency and improved luminescence from these metal ions.…”