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Inorganic phosphors based on rare earth elements are commonly used as scintillation materials due to their high chemical and radiation resistance. In this work, we study gadolinium oxyselenide as a new phosphor material. The work describes a facile synthesis method for Gd 2 O 2 Se. Single crystal structure of this compound was determined for the first time: sp.gr. P ¯3 m 1 with a ​= ​3.8911(4) Å and c ​= ​6.8829(8) Å. Gd 2 O 2 Se is stable in the inert atmosphere and melts at 2075 ​± ​20 ​°C. This material is also stable when heated in air up to 720 ​°C. with the following oxidation and weight increase. This mass increase can be explained by the oxidation of Se2− to Se4+. Further temperature increase above 952°С leads to a sharp mass loss and the final mass of sample corresponds to full oxidation of Gd 2 O 2 Se to gadolinium oxide. The band gap of the material was estimated to be 3.6 ​eV. Photoluminescence spectrum for Gd 2 O 2 Se:Tb3+ shows the characteristic transitions in Tb3+ ion with the most intense green emission that corresponds 5D 4 → 7F J transitions. [Display omitted] • A powder of Gd 2 O 2 Se was obtained and the single crystal structure was determined: sp.gr. P ¯3 m 1, a ​= ​3.89Å, c ​= ​6.88 Å. • The melting point was found to be 2075 ​± ​20 ​°C. High air stability for this compound was demonstrated up to 720 ​°C. • The estimated value of the band gap is 3.6 ​eV. The photoluminescence of the Tb3+ doped sample was investigated. [ABSTRACT FROM AUTHOR]

Abstract Y 4 S 3 (Si 2 O 7 ) and its solid solutions (Y 1-x RE x ) 4 S 3 Si 2 O 7 (RE = Eu x = 0.010–0.085, RE=Tb x = 0.010–0.500) were quantitatively prepared by reaction of starting compounds in molten CsCl. Single crystal X-Ray analysis revealed the difference in preference Eu3+ occupancy for two independent RE-sites coming from volume difference of these sites. This effect is negligible for the Tb-containing solid solution due to smaller difference in radii Tb3+ and Y3+ ions. Tb3+-containing samples are luminescent with typical emission of Tb3+, while Eu3+-containing samples are not luminescent. The 1%Tb3+-containing sample emits in blue or in green color depending on the excitation wavelength. Measured melting points are 1545 ± 15 °С for all investigated samples (Y 1-x RE x ) 4 S 3 Si 2 O 7. Graphical abstract Due to two kinds of luminescence: matrix and Tb3+-ions, the sample Y 4 S 3 (Si 2 O 7 ):1%Tb3+ changes color of FL from blue to green depending on the excitation wave. fx1 Highlights • Y 4 S 3 (Si 2 O 7 ) and its Tb3+/Eu3+-containing solid solutions were synthesized. • It is revealed, the dopant occupancy preference exists on one of two Y-sites. • Matrix Y 4 S 3 (Si 2 O 7 ) has intrinsic luminescence property. • Y 4 S 3 (Si 2 O 7 ):1%Tb3+ sample can emit in blue or in green region. [ABSTRACT FROM AUTHOR]