The effect of oxygen vacancies (V O ) and the atmosphere influence on persistent luminescence (PersL) in Y 3 Al 2 Ga 3 O 12 (YAGG):Ce 3+ ,Yb 3+ are investigated by heating it in CO 2 , air, and 10% H 2 /90% Ar atmospheres. The V O -rich YAGG phosphors with outstanding PersL are successfully obtained by the common contribution of the reducing atmosphere and the incorporated Yb 3+ ions, and the concentration of oxygen vacancies in the phosphors is characterized by X-ray photoelectron spectroscopy and electron paramagnetic resonance measurements. Compared to the best sample prepared in neutral CO 2 , the reduced sample shows an increase of 30% in initial intensity and 100% in duration time, while the oxidized sample decreases drastically and shows a faint and undetectable PersL. The enhancement is mainly caused by the abundant formation of V O , which is achieved by the pairing of V O with Yb 2+ ions. The newly created V O by the reducing calcination is inferred to be adjacent to the Yb site and forms a compensation-type defect cluster due to the charge compensation effect. These findings reveal that understanding the effect and formation of V O is of great significance to design a high-performance phosphor.

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The Bi-doped Mg 2 Si 0:8 Sn 0:2 single phase compound is prepared by a solid state reaction (SSR)-spark plasma sintering (SPS) method. The effect of the Bi content on the thermoelectric properties of the Bi-doped Mg 2 Si 0:8 Sn 0:2 compound is mainly investigated. The results show that the thermoelectric properties of the obtained samples are sensitive to the Bi content. With the increase in Bi content, the electrical conductivity () and Seebeck coefficient () of the samples are increased, while the thermal conductivity () is decreased slightly between 300 K and 850 K. When the Bi content is greater than 3.0 at%, the sample shows a maximum figure of merit (ZT) value (1:17 AE 0:05) at 850 K.

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