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Three kinds of metal atoms with different valence electronic configurations, Bi (6s26p3), Y (4d15s2), and Ce (4f15d16s2), were selected to investigate the effect of A-site (La3+) doping on electronic band structure, photoelectric properties, and photocatalytic performance of LaFeO3 perovskite. It was identified that the Bi doped LaFeO3 presented significantly improved photocatalytic activity towards the reduction of CO2, while the Y or Ce doped LaFeO3 displayed decreased photocatalytic activity compared to the pristine LaFeO3. It was revealed that doping of all the three metal atoms resulted in narrowed band gap and thus extended light absorption of LaFeO3 by lowering its conduction band minimum (CBM). The recombination rate and mobility of the charge carriers were represented by the relative effective mass (D) between holes and electrons for pristine and A-site doped LaFeO3. The doping of Bi resulted in increased D value, attributed to the Bi 6s electron states at the valence band maximum (VBM), and thus promoted separation and transfer of the charge carriers and improved photocatalytic activity of LaFeO3. In contrast, the doping of Ce resulted in significantly decreased D value, induced by the highly localized Ce 4f hole states at the CBM, and thus higher recombination rate of the charge carriers and decreased photocatalytic activity of LaFeO3. Furthermore, the Y doped LaFeO3 with a slightly decreased D value presented slightly increased recombination rate of the charge carriers and thus decreased photocatalytic activity. Such a work provides new insights into the A-site doping in LaFeO3 perovskite, which should be helpful for optimizing the electronic band structure and activity of perovskite-type photocatalysts at atomic level. [ABSTRACT FROM AUTHOR]

The current research of Charpy impact mainly focuses on obtaining the ductile brittle transition temperature of materials by experiments. Compared with experiments, numerical simulation can study many problems with harsh conditions. However, there are still few studies on the influence of geometric factors such as side grooves. In this paper, the geometry of standard Charpy impact test is designed. Specimens with different widths and side grooves are tested. The finite element model of Charpy impact was established by ABAQUS software. Use test results and simulation results to verify each other. The effects of sample width, side groove depth and side groove bottom fillet on the impact fracture resistance of the sample were studied. The results show that the specimen width is positively correlated with the impact toughness of the specimen. The side groove greatly reduces the impact toughness of the material; the toughness of side groove decreases with the increase of depth; the fracture toughness of side groove decreases with the increase of fillet at the bottom of side groove. The proportion of toughness energy to impact energy of samples was analyzed. The results show that the toughness energy accounts for about 70% of the impact energy of the sample, which has little to do with the geometric characteristics of the sample. This study presents a reliable method for studying Charpy impact tests. The influence of geometric parameters is obtained, which provides a reference method for the study of impact toughness of high toughness materials. [ABSTRACT FROM AUTHOR]