Dual-emission center ratiometric optical thermometer based on Bi3+ and Mn4+ co-doped SrGd2Al2O7 phosphor.

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, SrGd2Al2O7:Bi3+,Mn4+, 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 Bi3+ and Mn4+, and the energy transfer between Bi3+ and Mn4+ give it excellent signal resolution and accurate temperature detection. The Sa of SrGd2Al2O7:0.04Bi3+,0.003Mn4+ phosphor reaches a maximum value of 8.573% K-1 at 473 K, and the corresponding Sr 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 SrGd2Al2O7:0.04Bi3+,0.003Mn4+ phosphor can be regarded as a prominent FIR-type temperature sensing material.

Ca2+ enhanced far-red emission performance and efficiency of SrGd2Al2O7:Mn4+ phosphor for the potential application in plant growth lighting.

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.