Irradiation-induced valence conversion of samarium ions in Na2SO4

• Published in: Applied physics. A, Materials science & processing Vol. 111; no. 2; pp. 587 - 591
• Main Authors: Rahman, Abu Zayed Mohammad Saliqur, Cao, Xingzhong, Wei, Long, Wang, Baoyi, Yu, Runsheng, Chen, Zhibi, An, Guangpeng, Sidike, Aierken
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.05.2013; Springer
• Subjects: Band spectra; Characterization and Evaluation of Materials; Cold working, work hardening; annealing, quenching, tempering, recovery, and recrystallization; textures; Condensed Matter Physics; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Conversion; Cross-disciplinary physics: materials science; rheology; Electrons and positron radiation effects; Emission; Exact sciences and technology; Excitation; Irradiation; Machines; Manufacturing; Materials science; Nanotechnology; Optical and Electronic Materials; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Phosphors; Photoluminescence; Physical radiation effects, radiation damage; Physics; Physics and Astronomy; Processes; Scanning electron microscopy; Spectral emissivity; Structure of solids and liquids; crystallography; Surfaces and Interfaces; Thin Films; Treatment of materials and its effects on microstructure and properties; Host Crystal; SmF3; Na2SO4; Thenardite; Scanning Electron Microscopy Measurement; Radiation effects; Scanning electron microscopy; Particle size; Fluence; Photoluminescence; Samarium fluorides; XRD; Heat treatments; Gamma radiation; Valence; Sodium; Electron irradiation; Phosphors; Sodium sulfate; Samarium ions
• ISSN: 0947-8396; 1432-0630
• DOI: 10.1007/s00339-012-7266-y

Na 2 SO 4 :Sm phosphors were synthesized by heating pure sodium sulphate with a small amount of SmF 3 at 950 °C. X-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements show that the particle size of as-synthesized phosphors is 58 and 60 nm, respectively. The samples were irradiated by 60 Co γ -rays with irradiation doses of 10–50 kGy at room temperature and by electrons with a total fluence of 6.7×10 16 e/cm 2 at a flux of 7.8×10 11 e/cm 2 ⋅sec. After exposure to γ -ray and high energy electron irradiations, as-synthesized phosphors show the conversion of Sm 3+ →Sm 2+ . The photoluminescence (PL) spectra of as-synthesized, γ -ray, and electron-irradiated phosphors obtained under 375 nm excitation consist of narrow emission bands with peaks at 563, 598, 644, and 704 nm, assigned to the 4 G 5/2 → 6 H J ( J =5/2,7/2,9/2, and 11/2) transitions within 4 f 5 electronic configuration of Sm 3+ . The PL spectra of irradiated phosphors under 570 nm excitation at room temperature consist of a broad band with a peak at 695 nm and an emission line at 685.9 nm on the broad band. The broad band is assigned to the 4 f 5 5 d →4 f 6 ( 7 F J ) transition and the emission line to the 5 D 0 →  7 F 0 transition within Sm 2+ . The PL and photoexcitation (PE) spectra at 10 K were well assigned to energy levels of Sm 2+ . Annealing at 473 K (200 °C) completely erased the Sm 2+ emission band within the detection limit at room temperature.