Analysis of structural defects and their influence on red‐emitting γ‐Al2O3:Mn4+,Mg2+ nanowires using positron annihilation spectroscopy

• Published in: Luminescence (Chichester, England) England), 2024-09, Vol.39 (9), p.e4881-n/a
• Main Authors: Hue, Pham Thi, Hue, Nguyen Thi Ngoc, Van Tiep, Nguyen, Trung, Nguyen Vu Minh, Phuc, Phan Trong, Nguyen, La Ly, Son, Lo Thai, Trang, Le Thi Quynh, Trung, Ngo Dang, Hung, Nguyen Quang, Tuyen, Luu Anh, Duy, Nguyen Hoang
• Format: Article
• Language: English
• Subjects: Aluminum oxide; Defects; Doping; Doppler sonar; Electron microscopy; Energy transfer; Luminescence; Magnesium; Manganese ions; Momentum; nanopores; Nanotechnology; Nanowires; Optoelectronic devices; Phosphors; Photoluminescence; Photons; Positron annihilation; positron annihilation spectroscopy; Reducing agents; Scanning electron microscopy; Spectroscopy; Spectrum analysis; Synthesis; Thermal conductivity; Voids; X-ray diffraction; γ‐Al2O3 nanophosphor
• ISSN: 1522-7235; 1522-7243; 1522-7243
• DOI: 10.1002/bio.4881

The present paper reported on the analysis of structural defects and their influence on the red‐emitting γ‐Al2O3:Mn4+,Mg2+ nanowires using positron annihilation spectroscopy (PAS). The nanowires were synthesized by hydrothermal method and low‐temperature post‐treatment using glucose as a reducing agent. X‐ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL), and photoluminescence excitation (PLE) were utilized, respectively, for determining the structural phase, morphology and red‐emitting intensity in studied samples. Three PAS experiments, namely, positron annihilation lifetime (PAL), Doppler broadening (DB), and electron momentum distribution (EMD), were simultaneously performed to investigate the formations of structural defects in synthesized materials. Obtained results indicated that the doping concentration of 0.06% was optimal for the substitution of Mn4+ and Mg2+ to two Al3+ sites and the formation of oxygen vacancy (VO)‐rich vacancy clusters (2VAl + 3VO) and large voids (~0.7 nm) with less Al atoms. Those characteristics reduced the energy transfer between Mn4+ ions, thus consequently enhanced the PL and PLE intensities. Moreover, this optimal doping concentration also effectively controlled the size of nanopores (~2.18 nm); hence, it is expected to maintain the high thermal conductivity of γ‐Al2O3 nanowire‐phosphor. The present study, therefore, demonstrated a potential application of γ‐Al2O3 nanowire‐phosphor in fabricating the high‐performance optoelectronic devices. PAS analyses for γ‐Al2O3:Mn4+,Mg2+ nanowires reveal the optimal doping concentration (0.06%) for the substitution of Mn4+ and Mg2+ to two Al3+ sites, the formation of oxygen vacancy (VO)‐rich vacancy clusters, and large voids (~0.7 nm) with less Al atoms and nanopores (~2.18 nm). Those characteristics consequently enhanced the photoluminescence and photoluminescence excitation intensities and maintain the high thermal conductivity of γ‐Al2O3 nanowire‐phosphor.