Dy3+-, Tb3+-, and Eu3+-activated NaCa4(BO3)3 phosphors for lighting based on near ultraviolet light emitting diodes

A variety of Dy3+-, Tb3+- and Eu3+-singly or doubly or triply activated NaCa4(BO3)3 phosphors for light emitting diodes applications were synthesized via a high temperature solid state reaction technique under an ambient atmosphere. These phosphors were studied by X-ray diffraction, scanning electron microscopy, photoluminescence excitation and emission spectra, Commission International de I'Eclairage chromaticity coordinates, and correlated color temperatures. The emission colors of Dy3+-, Tb3+-, and Eu3+-doped phosphors can be successfully tuned from green to yellow and then to white by appropriately changing the Tb3+ content and the excitation wavelengths. The correlated color temperatures can also be tailored from cold color to warm color. Furthermore, the energy transfer process from Dy3+ to Tb3+ in the Dy3+/Tb3+ codoped phosphors exists, which is discussed based on the luminescence spectra and energy level diagram analysis. The NaCa4(BO3)3:Dy3+, Tb3+, Eu3+ phosphors reported here demonstrate promising applications in the fields of near ultraviolet based light emitting diodes.