Tunable full-color emitting Na 2 Ba 6 (Si 2 O 7 )(SiO 4 ) 2 :Ce 3+ ,Eu 2+ ,Tb 3+ ,Mn 2+ phosphor for UV white LEDs: Photoluminescence and energy transfer

Tunable full-color emitting Na2Ba6(Si2O7) (SiO4)2:Ce3+,Eu2+,Tb3+,Mn2+ phosphors have been prepared and investigated. X-ray diffraction (XRD), photoluminescence (PL) spectra, absolute quantum yield and lifetimes were used to characterize the samples. When doped with Ce3+ or Eu2+ they present blue luminescence under UV excitation. Results of luminescence spectra and decay time measurements reveals that an energy transfer (ET) from Ce3+ to Tb3+ occurred mainly via a dipole–quadrupole mechanism, and the critical distances of the ion pairs (RC) were calculated by the spectral overlap method. The energy-transfer efficiencies of Ce3+ to Eu2+ are discussed in detail. Commission on illumination value of color tumble emission as well as luminescence quantum yield (9.8–42.1%) can be tuned by controlling the content of Ce3+, Tb3+ and Eu2+. A white LED with CIE chromaticity coordinates of (0.30, 0.41), superior color-rendering index (Ra) of 87.5 and correlated color temperature (CCT) of 6518 K was fabricated by combining a 365 nm UV-InGaN chip and a phosphor blend of white-emitting Na2Ba6(Si2O7) (SiO4)2:Ce3+,Eu2+,Tb3+,Mn2+ phosphor. All results suggest that it is suitable for UV white LEDs.