Xiu Li,Chen Chen,Faqiang Zhang,Hanliang Fang,Xintang Huang,Zhiguo Yi
Developing photostrictive materials with wide visible light response and desirable photostriction strength remains a great challenge in view of practical applications. Ferrites with rich physical and chemical properties have great potential in this regard. Here, the photostrictive performances of three ferrite materials, CdFe2O4, CaFe2O4, and YFeO3, with different crystal structures are systematically investigated. A large photostriction around 0.1% with a decent photostrictive efficiency of ∼10–11 m3/W is obtained for all the three ferrites under 405, 520, and 655 nm laser illumination. Further investigation reveals that the photothermal effect-induced expansion and the light-induced nonthermal part contribute almost equally to the measured shape deformation. In situ X-ray diffraction with external laser illumination in conjunction with the laser power-dependent Raman spectra analysis indicates that the strong photostriction is not a uniform deformation microscopically, which is closely related to the various degrees of response of the lattice planes to light and mainly attributed to the light-induced distortion of FeO6 octahedrons. Further analysis suggests a bond length rule to account for both the difference between their photostrictive performances and the screening of materials.
Substantial effort has been devoted to fabricating nanocrystalline lanthanum ferrite (LaFeO3), and calcination is the crucial process of crystallization in both high-temperature strategies and wet chemical methods. Lowering the calcination temperature gives the ability to resist the growth and agglomeration of nanoparticles, therefore contributing to preserve their unique nanostructures and properties. In this work, we prepared crystalline LaFeO3nanoparticles with a calcination process at 500 °C, lower than the calcination temperature required in most wet chemistry methods. Correspondingly, the experimental conditions, including stoichiometric ratios, pH values, precipitants, complexant regent, and the calcination temperatures, were investigated. We found that the crystalline LaFeO3was formed with crystalline NaFeO2after calcination at 500 °C. Furthermore, the structure of FeO6octahedra that formed in coprecipitation was associated with the process of crystallization, which was predominantly determined by calcination temperature. Moreover, an illusion of pure-phase LaFeO3was observed when investigated by X-ray diffraction spectroscopy, which involves amorphous sodium ferrite or potassium ferrite, respectively. These findings can help prepare nanostructured perovskite oxides at low calcination temperatures.Keywords:crystalline LaFeO3nanoparticles;coprecipitation;calcination;FeO6octahedra;perovskite
Xianhua Zhang,Chunlei Pei,Xin Chang,Sai Chen,Rui Liu,Zhi-Jian Zhao,Rentao Mu,Jinlong Gong
Modulating lattice oxygen in metal oxides that conducts partial oxidation of methane in balancing C–H activation and syngas selectivity remains challenging. This paper describes the discovery of distorting FeO6 octahedra in La1–xCexFeO3 (x = 0, 0.25 0.5, 0.75, 1) orthorhombic perovskites for the promotion of lattice oxygen activation. By combined electrical conductivity relaxation measurements and density functional theory calculations studies, this paper describes the enhancement of FeO6 octahedral distortion in La1–xCexFeO3 promoting their bulk oxygen mobility and surface oxygen exchange capability. Consequently, La0.5Ce0.5FeO3 with the highest FeO6 distortion achieves exceptional syngas productivity of ∼3 and 8 times higher than LaFeO3 and CeFeO3, respectively, in CH4 partial oxidation step with simultaneous high CO2 conversion (92%) in the CO2-splitting step at 850 °C. The results exemplify the feasibility to tailor the active lattice oxygen of perovskite by modulating the distortion of BO6 in ABO3, which ultimately influences their reaction performance in chemical looping processes.
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