Liu Yongtao,Duan Bin,Zhou Lin,Wu Yuxiang,Wang Fengyi,Ding Changchun,Hu Junshan
Here, this study reports single-band red upconversion emission in β-Ba 2 ScAlO 5 : Yb 3+ /Er 3+ phosphor by doping Mn 2+ . The optimum concentration of Mn 2+ ions in β-Ba 2 ScAlO 5 : Yb 3+ /Er 3+ phosphor was 0.20. The intensity of red and green emissions is increased by 27.4 and 19.3 times, respectively. Compared with the samples without Mn 2+ ions, the red-green integral strength ratio of β-Ba 2 ScAlO 5 : Yb 3+ /Er 3+ /Mn 2+ sample was significantly increased by 28.4 times, reaching 110.9. The UCL mechanism was explored by analyzing the down-conversion luminescence spectra, absorption spectra, UCL spectra, and upconversion fluorescence lifetime decay curves of Yb 3+ /Er 3+ /Mn 2+ co-doped β-Ba 2 ScAlO 5 . The enhancement of upconversion red light is achieved through energy transfer between defect bands and Er 3+ ions, as well as energy transfer between Mn 2+ ions and Er 3+ ions. In addition, the Mn 2+ doped β-Ba 2 ScAlO 5 : Yb 3+ /Er 3+ red UCL phosphors have great potential for ambient temperature sensing in the 298–523 K temperature range. The maximum sensitivity of β-Ba 2 ScAlO 5 : Yb 3+ /Er 3+ /Mn 2+ phosphor as a temperature sensor at 523 K is 0.0247 K −1 .
This work presents a comprehensive investigation of Ba 2 ScAlO 5 , a hexagonal perovskite-related oxide possessing intrinsic oxygen vacancies without chemical substitution. This material exhibits a high concentration of surface-adsorbed oxygen as indicated by XPS analysis, while O 2 -TPD confirms its significant intrinsic oxygen vacancy content. H 2 O-TPD confirms synergistic physisorbed water and chemisorbed OH - , enhancing Intermediate temperature proton transport. Based on the defect equilibrium model, the influence of oxygen partial pressure and water vapor pressure on the conductive behavior was systematically studied under different atmospheres and temperatures. The results demonstrate that the conduction mechanism transitions from mixed ionic-hole in dry air to proton-dominated transport under humidified conditions within 500-700 °C. Therefore, Ba 2 ScAlO 5 is a promising, undoped electrolyte candidate for intermediate-temperature proton-conducting ceramic devices.
Junyan Gao,Peng Liu,Jinshu Wang,Ruimin Zhang,Yunfei Yang,Wenyuan Zhou,Hexiong Liu,Junhao Sun
The size and distribution of Sc 2 O 3 in the composite powder precursor has great effect on the emission property of scandate cathode. By one-step in-situ synthesis method, the composite powder exhibits the structure of quasi-spherical Sc 2 O 3 nanoparticles grown in situ on the surface of W/Ir grains, and the obtained W–Ir cathode with 3wt % Sc 2 O 3 could provide the emission current density of 83.43 A/cm 2 at 900 °C b , which is higher than other W–Ir mixed matrix scandate cathodes and W matrix scandate cathode. The XRD results showed that the high emission ability depended on the high content of active phase α-Ba 2 ScAlO 5 and low content of non-active phase BaAl 2 O 4 . In-situ TEM has been applied to observe the microstructure evolution of the cathode surface at high temperature for the first time. A serial change in the microstructural features of cathode surface and the migration of Ba, Sc and O on the substrate surface has been found, confirming the formation of Ba-Sc-O active layer. The first-principles calculations indicate that the active substances (Sc) are more stable (low adsorption energy of − 8.58 eV) on the IrW matrix cathode surface than on the tungsten matrix cathode surface, which is consistent with the low evaporation rate of the active substance detected by TFMS technique. Besides, the interaction between the active substance and the matrix was strengthened due to more electron transfer of Sc (1.88 e) and Ba (1.45 e), therefore lowering the work function . The feasible preparation technique makes such a cathode promising for applications in high-power microwave devices.
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