Photoluminescent properties of tunable green-emitting oxynitride (Ba3−xSrx)Si6O12N2:Eu2+ phosphor and its application in white LEDs

Green emitting Eu2+-doped (Ba3−xSrx)Si6O12N2 solid solutions were synthesized through solid state reaction at 1350 °C for 10 h under a N2/H2 atmosphere. The XRD patterns revealed that the solid solution series of (Ba3−x−ySrx)Si6O12N2:yEu2+ with x value ranging from 0–0.6 were established. An efficient and intense tunable green light was observed by varying the cation Sr/Ba ratio. The emission spectra exhibited an entire shift towards long wavelength with increasing of x value, which was caused by large crystal field splitting and Stokes shift. The x value dependence of emission intensity was discovered and explained by the enhanced probability of electron from excited 4f state to 5d ground state via nonradioactive transition. Highly thermal stability and feasible color coordinates were verified. White LEDs with excellent photochromic properties were fabricated by packing GaN based blue chips and (Ba,Sr)3Si6O12N2:Eu2+ phosphors. All results indicated that the (Ba3−xSrx)Si6O12N2:Eu2+ phosphors were confirmed to be a promising candidate for pc-white LEDs in solid state lighting.