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Mn-based phosphors with the wavelength of 700–750 nm are an important category of far-red phosphors that have promising potential in the application of plant lighting, and the higher ability of the far-red light emitting of the phosphors is beneficial to plant growth. Herein, a series of Mn4+- and Mn4+/Ca2+-doped double perovskite SrGd2Al2O7 red-emitting phosphors with wavelengths centered at about 709 nm were successfully synthesized by means of a traditional high-temperature solid-state method. First-principles calculations were conducted to explore the intrinsic electronic structure of SrGd2Al2O7 for a better understanding of the luminescence behavior in this material. Extensive analysis demonstrates that the introduction of Ca2+ ions into the SrGd2Al2O7:Mn4+ phosphor has significantly boosted the emission intensity, internal quantum efficiency, and thermal stability by 170%, 173.4%, and 113.7%, respectively, which are superior to those of most other Mn4+-based far-red phosphors. The mechanism of the concentration quench effect and the positive effect of co-doping Ca2+ ions in the phosphor were extensively explored. All studies suggest that the SrGd2Al2O7:0.1%Mn4+, 11%Ca2+ phosphor is a novel phosphor that can be used to effectively promote the growth of plants and regulate the flowering cycle. Therefore, promising applications can be anticipated from this new phosphor. [ABSTRACT FROM AUTHOR]

In recent years, more and more attention has been paid to optical temperature sensing, and how to improve its accuracy is the most important issue. Herein, a new temperature sensing material, SrGd 2 Al 2 O 7 :Bi 3+ ,Mn 4+ , based on fluorescence intensity ratio was designed in this work. It has both blue-purple and red luminescence under 300 nm excitation, and the dual-emitting centers with distinct colors, the different thermal sensitivities of Bi 3+ and Mn 4+ , and the energy transfer between Bi 3+ and Mn 4+ give it excellent signal resolution and accurate temperature detection. The S a of SrGd 2 Al 2 O 7 :0.04Bi 3+ ,0.003Mn 4+ phosphor reaches a maximum value of 8.573% K -1 at 473 K, and the corresponding S r is 1.927% K -1 , both of which are significantly better than those of most other reported optical temperature sensing materials. Taking all the results into account, the SrGd 2 Al 2 O 7 :0.04Bi 3+ ,0.003Mn 4+ phosphor can be regarded as a prominent FIR-type temperature sensing material., Competing Interests: On behalf of all authors, the corresponding author states that there is no conflict of interest which could have appeared to influence the work reported in this paper., (This journal is © The Royal Society of Chemistry.)