Blue-light-excited red emission in a CaO:Eu phosphor

Introducing multiple luminescent centers into the matrix crystal is an effective measure to endow this class of materials with new optical properties. Here, the coexistence of Eu2+ and Eu3+ was achieved in CaO matrix crystal from CaCO3:Eu3+ by a double crucible carbon reduction method. Under NUV-light excitation, the PL spectrum of CaO:Eu consists both a broad band of Eu2+ and several sharp lines of Eu3+. More significantly, CaO:Eu exhibits broadband emission at λmax = 661 nm upon excitation at 466 nm. Calcium vacancies (VCa) in CaCO3:Eu3+ increase the reduction rate, thereby enhancing the emission intensity of Eu2+. The high Ra (91.2) and LE (49.36 lm/w), and low CCT (3435 K) of as-fabricated WLEDs suggest that the prepared CaO:Eu are promising materials for WLEDs applications. The findings provide a new avenue for exploring novel Eu2+-activated simple oxide-based red phosphors.