Energy transfer and thermal regression mechanism of color-tunable phosphor Sr8La2(PO4)3.5(SiO4)2(BO4)0.5BO2: Ce3+, Tb3+

• A color-tunable phosphor is firstly synthesized by the solid state reaction.
• The energy transfer mechanism between Ce3+ and Tb3+ is carefully studied.
• The phosphor shows an interesting temperature-dependent luminescence behavior.
• By configurational coordinate diagram, thermal regression mechanism is explained.

A series of phosphosilicate phosphors Sr8La2(PO4)3.5(SiO4)2(BO4)0.5BO2: Ce3+, Tb3+ are synthesized by solid-state reaction for the first time. The XRD Rietveld refinement presents that the compound crystallizes in a trigonal crystal system with space group P3¯ (No. 147). Under the excitation of 340 nm, commonly blue and yellowish green emissions from Ce3+ and Tb3+ are detected and can generate the color-tunable light with chromaticity coordinates from (0.188, 0.095) to (0.351, 0.517) by changing the ratio of Ce3+/Tb3+. By the photoluminescence spectra, decay times and energy transfer efficiency, the mechanism of energy transfer between Ce3+ and Tb3+ has been carefully investigated. With the increase of temperature, the Ce3+ or Tb3+ single doped sample shows an excellent thermal property, but when the Ce3+ and Tb3+ are co-doped into the host, the thermal property of sample seriously degenerates. This result indicates that the change of temperature can affect the energy transfer between Ce3+ and Tb3+ strongly and based on the configurational coordinate diagram, this phenomenon is explained reasonably.

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