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In this study, we successfully prepared red‐emitting AlN:Mn2+ spherical phosphors by using nitrogen pressure–assisted carbothermal reduction–nitridation method. The optimum preparation parameters were explored by changing nitrogen pressure, CaF2 content, reaction temperature, and the amount of MnCO3. It was confirmed that uniform spherical shape, large particle size, less impurity content, and suitable Mn2+ concentrations could effectively enhance the luminous intensity of AlN:Mn2+ phosphors. The structural compositions of the AlN:Mn2+ phosphors were characterized by X‐ray diffraction and X‐ray photoelectron spectroscopy, indicating that Mn2+ ions were successfully doped into AlN lattice by substitution of Al3+ ions, thus providing the red‐emitting luminescence centers. Based on the experimental results, we further proposed the underlying growth mechanism of spherical AlN phosphors. It was suggested that an adequate amount of liquid Ca‐aluminates was essential to achieve uniform spherical morphology and high fluorescence efficiency. [ABSTRACT FROM AUTHOR]

A novel deep‐red‐emitting phosphor Ca2ScNbO6:Mn4+ is prepared via a high‐temperature solid‐state reaction and its luminescent properties are systematically investigated. The results show that Mn4+‐activated Ca2ScNbO6 phosphors have broad absorption in ultraviolet region, and show bright deep‐red emission at 692 nm. The optimal doping concentration, crystal‐field strength, internal quantum efficiency, and mechanism of concentration and thermal quenching effects are discussed in detail. Moreover, NaF flux is screened out to improve both luminescent intensity and morphology of the phosphor. Finally, a red light‐emitting diode (LED) lamp is fabricated with as‐prepared Ca2ScNbO6:Mn4+ phosphors and a 365 nm LED chip. The electroluminescence spectra show a good overlapping with phytochrome PR and PFR absorbance. The results provided the as‐synthesized Ca2ScNbO6:Mn4+ phosphors a great potential in plant growth lighting. [ABSTRACT FROM AUTHOR]

Mn4+‐activated double‐perovskite type Ca2ScSbO6 (CSS) phosphors were synthesized via a high‐temperature solid‐state reaction. The phase purity and crystal structure of obtained samples were investigated by powder X‐ray diffraction (XRD). The successful incorporation of Mn4+ ions into CSS lattice was confirmed by the combination of energy‐dispersive X‐ray spectra (EDX) and X‐ray photoelectron spectra (XPS) results. The luminescent properties of the CSS phosphors, including the photoluminescence (PL) and PL excitation (PLE) spectra, commission international de l'clairage (CIE) chromaticity coordinates, fluorescence decay curves, quantum yields and temperature‐dependent PL spectra, were investigated in detail. Under 310‐nm excitation, the optimized CSS:0.3%Mn4+ phosphor exhibited bright deep‐red emission covering a narrow band from 640 nm to 720 nm, which overlaps with the absorbance of phytochromes. The Racah parameters B, C, and local crystal strength Dq were calculated to be 870, 2703, and 1984 cm–1, respectively. Particularly, the emission intensity of CSS:0.3%Mn4+ still remained 61.4% at 423 K compared with that at room temperature. Therefore, all these outstanding luminescent properties provided the as‐synthesized phosphors a great potential in plant growth lighting. [ABSTRACT FROM AUTHOR]

In this study, blue‐emitting AlN:Eu2+ spherical phosphors were successfully synthesized for the first time by the carbothermal reduction nitridation (CRN) method, assisted with high nitrogen pressure, appropriate synthesis temperature, and the addition of CaF2. The influence of typical experimental parameters, such as N2 pressure, heating temperature, CaF2 content and Eu2+ concentration on the morphologies and luminescence properties of AlN phosphors were comprehensively investigated. The formation mechanism of spherical morphology were significantly proffered, indicating that sufficient liquid Ca‐aluminates during the AlN growth stage were essential for the spheroidization process under the action of surface tension. The synthesized AlN:Eu2+ spherical phosphors presented an intense blue emission band centered in the range of 427‐ 476 nm relative to the reaction temperature. The lifetime of AlN:Eu2+ phosphor was calculated to be around 1.89 μs. The temperature‐dependent PL spectra suggested that the emission band did not shift until 225°C. In addition, the spectral analysis strongly suggested that the luminescence property of AlN:Eu2+ phosphors was significantly enhanced by the large particle size, spherical morphology, reduced impurity content, and appropriate Eu2+ concentration. [ABSTRACT FROM AUTHOR]