Improved luminescence of CaAl12-xGaxO19:Cr3+ near-infrared phosphor based on Sr2+ and Ga3+ substitution

•Novel near-infrared phosphors Ca1-ySryAl12-xGaxO19:0.12Cr3+ were synthesized by a high-temperature solid-phase method.•The use of Ga3+ to replace part of Al3+ to change the crystal field strength resulted in an effective broadening of the spectrum.•The Debye temperatures before and after Sr2+ substitution were calculated by first principles, the theory predicted that the thermal stability of the samples would be enhanced, and the correctness of the theory was confirmed experimentally.•The multi-component substitution strategy is a feasible way to obtain high-quality phosphors for LED lighting by both obtaining luminescent materials with broad spectral bands and improving the thermal stability of the materials.