Improvement of emission intensity, colour rendering index and thermal stability of Ca9Ce(PO4)7:Eu2+,Mn2+via H3BO3 doping

Ca8.78Ce (PO4)7:0.06Eu2+,0.16Mn2+,xH3BO3 phosphors were synthesized by a high-temperature solid-state reaction method. XRD patterns of the samples indicate that H3BO3 doping does not change the phase formation. However, H3BO3 doping can change the emission intensities of Ce3+, Eu2+, Mn2+ and the energy transfer efficiencies of Ce3+–Eu2+ and Ce3+–Mn2+. The reason for this is that H3BO3 doping changes the luminescent centre and the distance between different luminescent centres to some degree. When the ligand polyhedron volume decreases, the lifetime and emission intensity of the luminescent centre will increase. When the distance between Ce3+ and Eu2+/Mn2+ decreases, the energy transfer efficiency between them will increase. In Ca8.78Ce(PO4)7:0.06Eu2+,0.16Mn2+,xH3BO3, the average volume of an [(Eu/Mn)1/2/3–O8/9] polyhedron will decrease from 27.511 A3 to 21.847 A3, and the average distance between Ce and (Eu/Mn)1/2 will decrease from 3.702 A to 3.573 A with increased doping amounts of H3BO3 from 0 to 7. Meanwhile, the emission intensity and lifetime of Ce3+ decrease, and those of Eu2+/Mn2+ increase. Furthermore, the energy transfer efficiency from Ce3+ to Eu2+/Mn2+ and the quantum efficiency are improved. H3BO3 doping improves the ratio of red, green and blue colours of the spectrum, which improves the colour rendering index of materials from 80.5 to 90.7. H3BO3 doping also improves the thermal stability of the material to some degree. The quenching temperature of Eu2+ is improved from 75 °C to 100 °C.