A study by powder X-ray diffraction (using the Rietveld method of structure refinement), 57 Fe Mo ¨ssbauer spectroscopy, and magnetization measurements have shown that YFe 4 Al 8 , although a stable phase at 1070 K (space group I4/mmm, a ) 8.7604(7) Å, c ) 5.0504(5) Å), does not melt congruently. Large single crystals obtained by the Czochralski method from bulk charges containing Y, Fe, and Al in the atomic ratios 1/4/8 have final compositions YFe 4.2(2) Al 7.8(2) (space group I4/mmm, a ) 8.7303(3) Å, c ) 5.0486(2) Å). YFe 4.2 Al 7.8 shows an antiferromagnetic-like transition at T ord ) 100 K, in contrast with YFe 4 Al 8 (T ord ) 180 K). In YFe 4.2 Al 7.8 a distribution of the moduli of the Fe magnetic moments (µ Fe ) is observed between 100 K and ∼50 K. Below 45 K the Fe atoms on the 8f site have two different values of µ Fe and on the 8j sites only one is observed. The relative values of the µ Fe may be understood on the basis of the Fe-Fe intersite exchange interactions.

No abstract

No abstract

A novel immobilized Ca 0.6 Ho 0.4 MnO 3 photocatalyst has been developed with high photocatalytic activity for Rhodamine 6G (Rh6G) photodegradation under visible light irradiation. The nanocrystalline Ca 0.6 Ho 0.4 MnO 3 films were successfully deposited by RFmagnetron sputtering on unheated quartz glass substrates using Ca 0.6 Ho 0.4 MnO 3 powder as sputtering target and its photocatalytic functionalities have been explored. The visible-lightresponsive photocatalytic activity of Ca 0.6 Ho 0.4 MnO 3 films was evaluated by the photodegradation of Rh6G aqueous solutions under visible light irradiation. The reusability of Ca 0.6 Ho 0.4 MnO 3 films on fresh dye samples was studied, showing an efficient reuse, without decreasing the photocatalytic decolorization efficiency. Furthermore, X-ray diffraction of the reused films did not reveal additional phases indicating high photochemical stability of the films even after reusing them in successive runs. The photocatalytic efficiency of the nanocrystalline Ca 0.6 Ho 0.4 MnO 3 films was further compared with TiO 2 films also produced by sputtering and the results revealed a significant improvement in photocatalytic activity over TiO 2 under visible light irradiation. Almost complete photodecolorization of a 5 ppm Rh6G solution was achieved in 4 h, while only 64% of dye degradation was observed in TiO 2 photoassisted process. This work provides a feasible route to fabricate high-performance immobilized ABO 3 -based nanomaterials, and the finding opens up a new venue for designing visible light sensitive ternary compounds for photocatalytical applications.

No abstract

No abstract

No abstract

No abstract