Solvothermal synthesis and Curie temperature of monodispersed barium titanate nanoparticles

Barium titanate (BaTiO3) nanoparticles with various particle sizes were prepared by a solvothermal method X-ray powder diffraction (XRPD) patterns show that the as-prepared powders are of pure perovskite BaTiO3 Scanning electron microscopy (SEM) reveals that all the particles of BaTiO3 with different sizes are dispersed homogenously and have uniform size The room temperature and in situ high temperature XRD analyses indicate that both the proportion of the tetragonal phase and the Curie temperature of BaTiO3 Increase with increasing particles size The effects of the reaction parameters such as the concentration of reactants the polarity of solvent the reaction temperature and the amount of surfactant on the size morphology and uniformity of BaTiO3 nanoparticles are studied in detail (C) 2010 Elsevier B V All rights reservedNatural Science and Engineering Research Council of Canada (NSERC) ; National Natural Science Foundation of China [20725310, 91022020]; National Basic Research Program of China [2007CB815303

Polymorphic structures and properties of lead chromium phosphate Pb3Cr2(PO4)(4)

Single crystals of lead chromium phosphate Pb3Cr2(PO4)(4) were grown by a flux technique and characterized by X-ray powder and single crystal diffraction, differential thermal analysis, polarized light microscopy and magnetic measurements. Two polymorphic structures have been identified: a monoclinic Pb3Cr2(PO4)(4) of space group P2(1)/C (14) and a tetragonal Pb3Cr2(PO4)(4) of space group P4(1)2(1)2 (94), and their phase correlation is described. Both structures consist of a three-dimensional framework which is composed of PO4 tetrahedra and CrO6 octahedra connected via vertices. Lead ions are situated at the cavities of the framework, but the positions of lead ions in the monoclinic Pb3Cr2(PO4)(4) are different from those in the tetragonal Pb3Cr2(PO4)(4). The Pb3Cr2(PO4)(4) crystals are found to exhibit interesting physical properties. The ferroelastic domain structures reveal characteristic patterns of the tetragonal and the monoclinic symmetry of the crystals. The birefringence of the tetragonal crystals decreases with increasing temperature. The monoclinic crystal is found to undergo a series of magnetic phase transitions upon cooling, from a paramagnetic phase (from room temperature down), to an antiferromagnetic phase below T-N = 6K, and then to a weakly ferromagnetic phase below the Curie temperature T-C = 4 K, with a magnetic hysteresis loop displayed at 2 K.Natural Science and Engineering Research Council of Canada (NSERC) ; National Natural Science Foundation of China [20725310, 20673085]; National Basic Research Program of China [2007CB815303

Room-temperature ferromagnetic/ferroelectric BiFeO3 synthesized by a self-catalyzed fast reaction process

Bismuth ferrite BiFeO3 has attracted a great deal of interest because of its multiferroic properties. However, BiFeO3 synthesized by conventional methods in the forms of single crystals, ceramics or thin films only exhibit ferroelectricity and antiferromagnetic order at room temperature, with weak ferromagnetism appearing at very low temperatures. To fully explore the potential of multiferroism in such applications as new memory devices, it is necessary to synthesize materials that show ferromagnetic order at room temperature as well, which will a priori allow for magnetoelectric coupling. In this paper, we report a new synthetic technique for the synthesis of BiFeO3 that exhibits unusual ferromagnetic properties. This method involves a low temperature fast solid state reaction based on tartaric acid. The mechanism of the reaction deduced from thermogravimetric analysis (TGA) and differential thermal analysis (TGA) suggests that a self-catalyzed process in the presence of iron and bismuth oxides triggers the oxidation of tartaric acid at low temperature and gives out a large amount of heat, which, in turn, leads to the formation of BiFeO3. The BiFeO3 synthesized in this way is ferromagnetic. The origin of the unusual ferromagnetism is supposed to be associated with point defects of oxygen vacancies generated during the self-catalyzed extremely fast exothermic reaction, which suppress the spin circular cycloid in BiFeO3. Ferroelectric hysteresis loops are displayed in the BiFeO3 samples. The presence of room temperature ferromagnetic and ferroelectric orders makes BiFeO3 a truly multiferroic material potentially interesting in such applications as magnetoelectric devices.Natural Science and Engineering Research Council of Canada (NSERC) ; National Natural Science Foundation of China [20725310, 20673085]; National Basic Research Program of China [2007CB815303

Syntheses and characterizations of rare earth compounds RE(HCO2)(3)(HNO2) (H2CO2) (RE = Y, Tb, Dy, Ho, Er, Yb, Tm)

A series of novel inclusion compounds with compositions of RE(HCO2)(3)(HNO2)( H2CO2) (RE = Y, Tb, Dy, Ho, Er, Yb, Tm) were synthesized and structures were characterized by X-ray methods. The orthorhombic structure was shown to be a new type with a non-centrosymmetric space group (20) C222(1) by single crystal structure determinations. It is characterized by networks of rare earth centered square anti-prisms formed by eight oxygen atoms through bridging carbon and nitrogen atoms. The guest formic acid molecules H2CO2 are distributed inside the open tunnels along the crystallographic a axis. The magnetic susceptibility measurements show the heavy rare earth compounds follow the Curie-Weiss law and the calculated numbers of Bohr magnetons are consistent with the RE3+ ions. The yttrium compound shows very weak temperature independent paramagnetism

Room-Temperature Weak Ferromagnetism Induced by Point Defects in alpha-Fe(2)O(3)

Natural Science and Engineering Research Council of Canada (NSERC); National Natural Science Foundation of China [20725310, 20673085]; National Basic Research Program of China [2007CB815303]Unusual room-temperature weak ferromagnetism alpha-Fe2O3 was prepared by heating the mixture of commercial alpha-Fe2O3 (as raw material) and tartaric acid at a mild temperature of 250 degrees C. This reaction involves a Fast heating and cooling process resulting from the self-catalyzed oxidation of tartaric acid. Careful chemical analyses confirmed that no any ferromagnetic impurities, such as Fe. Fe3O4, amorphous iron oxide and gamma-Fe2O3, were present in the treated sample. The unusual weak ferromagnetism was then attributed to the formation of a large amount of point defects in the treated sample during the peculiar synthetic process. Such a mechanism is supported by the result of annealing, which reduces the amount of point defects and thereby reestablishes the original antiferromagnetism in alpha-Fe2O3

Room-Temperature Weak Ferromagnetism Induced by Point Defects in alpha-Fe2O3

Unusual room-temperature weak ferromagnetism alpha-Fe2O3 was prepared by heating the mixture of commercial alpha-Fe2O3 (as raw material) and tartaric acid at a mild temperature of 250 degrees C. This reaction involves a Fast heating and cooling process resulting from the self-catalyzed oxidation of tartaric acid. Careful chemical analyses confirmed that no any ferromagnetic impurities, such as Fe. Fe3O4, amorphous iron oxide and gamma-Fe2O3, were present in the treated sample. The unusual weak ferromagnetism was then attributed to the formation of a large amount of point defects in the treated sample during the peculiar synthetic process. Such a mechanism is supported by the result of annealing, which reduces the amount of point defects and thereby reestablishes the original antiferromagnetism in alpha-Fe2O3.Natural Science and Engineering Research Council of Canada (NSERC) ; National Natural Science Foundation of China [20725310, 20673085]; National Basic Research Program of China [2007CB815303

Correction: Alkaline Ceramidase 3 Deficiency Results in Purkinje Cell Degeneration and Cerebellar Ataxia Due to Dyshomeostasis of Sphingolipids in the Brain

<p>Correction: Alkaline Ceramidase 3 Deficiency Results in Purkinje Cell Degeneration and Cerebellar Ataxia Due to Dyshomeostasis of Sphingolipids in the Brain</p