Synthesis of blue‐emitting AlN:Eu²⁺ spherical phosphors by carbothermal reduction nitridation method

Abstract

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.

Synthesis and luminescence properties of red‐emitting AlN:Mn2+ spherical phosphors

“…When the temperature was relatively low at 1600°C, the reaction rate was slow, and the liquid phase in the reaction system was insufficient to completely coat AlN particles. There was a lack of driving force for the growth to spherical morphology, so the reaction products presented irregular angular morphology 27 . When the temperature reached to 1700°C, CaF 2 , and Al 2 O 3 reacted faster, more liquid phase was generated in the reaction system to fully wrap the AlN particles.…”

“…There was a lack of driving force for the growth to spherical morphology, so the reaction products presented irregular angular morphology. 27 When the temperature reached to 1700 • C, CaF 2 , and Al 2 O 3 reacted faster, more liquid phase was generated in the reaction system to fully wrap the AlN particles. As a result, the material transfer was accelerated, resulting in the spherical shape.…”

Effect of annealing temperature on Eu2+ and Eu3+ ratios in AlN:Eu thin films

“…[11][12][13] It has a wide band gap of 6.2 eV and is known to possess various levels due to vacancy defects and interstitial defects (V Al , V N , i Al , i Ni ), [14][15][16] which have been shown in previous studies to emit blue light in the 300 ∼ 400 nm wavelength region. [17][18][19] Eu is widely used as an activator (dopant) for phosphors and optical materials. [20][21][22] The luminescence of Eu 2+ covers a wide range of wavelengths, showing blue to green emission (360-530 nm).…”