Photoluminescence properties of Ce3+/Mn2+ doped calcium zirconium silicate phosphors with energy transfer for white LEDs

A series of Ce3+ doped and Ce3+/Mn2+ co-doped calcium zirconium silicate CaZrSi2O7 (CZS) phosphors have been synthesized via conventional high temperature solid state reactions. The luminescence properties, energy transfer between Ce3+ and Mn2+ have been investigated systematically. Under 320 nm excitation, the phosphor CZS: 0.05Ce3+ exhibit strong blue emission ranging from 330 nm to 500 nm, attributed to the spin-allowed 5d-4f transitions of Ce3+ ions. There are two different emission centers of Ce3+ ions, Ce3+(I) and Ce3+(II). The emission spectra of Ce3+, Mn2+ co-doped phosphors shows a broad emission around 550 nm corresponding to the 4T1(4G)-6A1(6S) spin-forbidden transition of Mn2+. The energy transfer between Ce3+ and Mn2+ is detected and the transfer efficiency of Ce3+(II) to Mn2+ is faster than that of Ce3+(I) to Mn2+. The resonant type is identified via dipole-dipole mechanism. Additionally, a blue-shift emission of Ce3+ and a red-shift emission of Mn2+ have been observed following the increase of Mn2+ content in relation to the energy transfer. Thermal quenching has been investigated and the emission spectra show a blue-shift with the temperature increases, which have been discussed in details. CZS: 0.05Ce3+, yMn2+ phosphors can be tuned from blue to white and even to yellow by adjusting the Mn2+ content. All the results indicate that CZS: Ce3+, Mn2+ phosphor have a potential application for near-UV LEDs.