Luminescence in some tantalate host lattices

The luminescence of the following systems are reported: ScTa_1−xNb_xO₄, Li₃Ta_1−xNb_xO₄, CaTa_2−2xNb_2xO₆ and Mg₄Ta_2−2xNb_2xO₉. The dependence of the luminescence properties on x becomes more pronounced if the distance between the pentavalent ions becomes shorter. In these systems the NbO₆ group gives an efficient blue emission at 300°K. The compound Mg₄Ta₂O₉ gives an efficient ultraviolet emission at 300°K. At 77°K both Mg₄Nb₂O₉ and Mg₄Ta₂O₉ show in addition a weaker emission peaking at wavelengths longer than the wavelength of the room temperature emission. This low-temperature emission can be excited by radiation with wavelengths longer than that of the absorption edge. The Mn²⁺ ion in Mg₄Ta₂O₉Mn acts as an efficient activator with a deep-red emission.