For the purpose of development of highly energy-efficient light sources, one needs to design highly efficient green, red and yellow phosphors, which are able to absorb excitation energy and generate emissions. Using double activation, energy can be transferred from one luminescent activator to the other one, resulting in more efficient or brighter device operation. Co-activators can be added to a host material to change the color of the emitted light. The incorporation of Eu3+ or Tb3+ ions into the CaWO4 crystal lattice modifies the luminescence spectrum due to the formation of the emission centers that generate the specific red and green light. Very efficient new red phosphors based on YNbO4 and doped by Eu3+, Ga3+, Al3+ allow recommend these materials as good candidates for different applications including LED and X-ray intensifying screens. For double activated TAG with Ce3+ and Eu3+ and for different mole ratio Ce/Eu the color temperature changes from 5500 K (0.331, 0.322) up to 4200 K (0.370, 0.381) and the light becomes ‘‘warmer’’. Application of TAG:Ce,Eu in the light emitting device shows the better chromaticity coordinates of luminescence and color rendering index of LEDs. Combination of Eu2+ with Dy3+ in SrAl2O4 matrix allows us to create a material that emitted bright light for hours after ending the excitation. In this contribution we present our results on producing some efficient phosphors with improved luminescence properties for different applications: LED and X-ray intensifying screens, marine artificial reefs, biology and medicine.