Search

CaWO 4 and Ca 0.72 La 0.28 WO 4 samples were synthesized via mild hydrothermal method at 180 °C. Composition, phase purity, morphology and W element binding energy were characterized by induced couple plasma atomic emission spectrum (ICP-AES), powder x-ray diffraction (XRD), scanning electron microscopy (SEM), x-ray energy dispersive spectroscopy (EDS), and x-ray photoelectron spectroscopy (XPS). UV–vis absorption spectroscopy shows absorption peak shift due to La 3+ doping, which induced to the presence of mixed valence states of W 5+ and W 6+ in scheelite-type structure compound. Hence, blue shift of UV–vis absorption from 350 nm to 405 nm was observed in La 3+ -doped calcium tungstate. [ABSTRACT FROM AUTHOR]

We report the synthesis of LaCr1−xMnxO3 (x = 0.1, 0.2, and 0.3) single crystal microcubes via a mild hydrothermal method. The as-synthesized LaCr1−xMnxO3 samples were crystallized into the Pnma space group with uniform particle size and cubic morphology. The lattice parameters increased as the doping level of Mn increased from x = 0.1 to 0.3. XPS characterization of the samples showed that the valence states of Cr and Mn are both +3. A temperature-dependent magnetization study indicated a clear transition point of canted-antiferromagnetic to paramagnetic behaviour from 3–380 K, with their Neel transition points located between 246–265 K. The isothermal magnetic hysteresis of the LaCr1−xMnxO3 samples show that they possess the same coercive field strength but a linear increment of remnant magnetization with increasing Mn doping level. A temperature-dependent magnetic entropy change study indicated that the samples show a maximum ΔS of 0.4247 J kg−1 K−1 for LaCr0.7Mn0.3O3 at 40 K for ΔH = 6 T. Arrott plots of M2versus H/M indicate a second-order magnetic phase transition for all of the as-synthesized LaCr1−xMnxO3 samples. All these results suggest that the promotion of magnetization was successfully performed by hydrothermally doping Mn in a LaCrO3 lattice. This study provides a design and synthesis strategy to increase the ferromagnetic exchange in weak magnetization materials. [ABSTRACT FROM AUTHOR]

In this work, Ce 3+ singly doped, Ce 3+ /Tb 3+ and Eu 3+ /K + co-doped BaSiF 6 phosphors have been synthesized via a one-step hydrothermal method. Colour-emitting may be varied by changing relative intensities of Ce 3+ and Tb 3+ through energy transfer in BaSiF 6 phosphors. We found that HF and H 3 PO 4 could facilitate the dissolution of SiO 2 under hydrothermal condition and obtained pure BaSiF 6 host material. The crystal structure and the composition were analysed, and the morphology was examined. Furthermore, the corresponding photoluminescence properties of the rare earth doped BaSiF 6 were characterized. [ABSTRACT FROM AUTHOR]

The double peroskite Lu 2 NiMnO 6 was synthesized by a facile hydrothermal method. X-ray power diffraction (XRD) analysis shows it adopts monoclinic structure with space group P2 1 /n , indicating an ordered arrangement at B sites. Valence states analysis done by XPS shows Ni 2+ /Mn 4+ configuration. Raman spectrum reveals an ordered structure in the sample, in agreement with the XRD results. The degree of ordering was greatly enhanced after the sample was annealed at 873 K. Magnetism of the as-grown and annealed samples was analyzed using DC and AC magnetization, as well as Magnetization-Hysteresis. Dielectric anomaly independent on frequency was observed close to the magnetic ordering temperature, indicating the possibility of ferroelectricity and further magnetoelectric coupling. [ABSTRACT FROM AUTHOR]

A series of BaSiF6:xEu3+ (x = 3-20%), BaSiF6:15%Eu3+/15%K+, and BaSiF6:3%Eu3+/2%Tb3+ down-conversion phosphors are hydrothermally prepared using hydrated SiO2 and NH4HF2 as metal chelating agents. [ABSTRACT FROM AUTHOR]

Single crystals of β-Li3VF6 (I) and Na3VF6 (II) are obtained by hydrothermal reaction of stoichiometric amounts of NH4VO3, NH4HF2, LiCl (NaCl), and fumaric acid (pH 4-6, autoclave, 240 °C, 24 h) without the need for HF. [ABSTRACT FROM AUTHOR]

The hydrothermal synthesis and magnetic, dielectric and ferroelectric property characterization of ABO3-perovskite GdFe1−xCrxO3 (0 ＜ x ＜ 1) are reported. The mineralizer KOH plays a critical role in the perovskite structure of the sample. The Fe/Cr ratio of the final crystal is controlled by the alkalinity in the initial reaction mixtures. The lattice parameters and magnetic ordering transition temperature have a close relationship with the Fe/Cr ratio. The temperature dependent magnetic properties of GdFe1−xCrxO3 (0 ＜ x ＜ 1) samples show a close relationship with substituent ratios of Cr3+. The occurrence of ferromagnetic behavior in all of the as-prepared samples comes from the coexistence of canted-antiferromagnetism due to the double exchange effect of Fe–O–Fe and Cr–O–Cr and ferromagnetism due to superexchange interaction of Fe–O–Cr. A large spontaneous polarization was observed in GdFe1−xCrxO3 at room temperature, exhibiting a clear ferroelectric hysteresis loop, which indicates the ferroelectric behavior in this system. This work not only provides an effective route to the controllable synthesis of B-site doped REFe1−xCrxO3 perovskite structure materials, but also presents a comprehensive study of the tunable effect of ionic doping on ferroelectric properties. [ABSTRACT FROM AUTHOR]

Perovskite structured rare-earth chromites (RECrO3) are an interesting family of functional materials due to their wide application in numerous areas. Various methods have been used to synthesize this family of materials; however, such methods usually need a high temperature crystallization process above 800 °C, and only produce polycrystalline ceramics. Herein, a series of RECrO3 single crystal samples with uniform particle sizes were prepared via a mild hydrothermal method with temperatures as low as 240–260 °C, and the synthesis conditions were studied in detail. Samples of LaCrO3, PrCrO3, and NdCrO3 were indexed to the Pnma space group, whereas SmCrO3 was indexed to Pbnm. The shapes of the crystals changed from cubic to plate as a result of the crystal lattice distortions induced by the reduction in the size of the A-site rare-earth cation. Raman spectra of the samples showed characteristic vibration modes of CrO6 clusters. Temperature dependent magnetization studies showed a transition from antiferromagnetism to paramagnetism in all the samples. Higher maximum and residual magnetization was achieved in all the hydrothermally prepared samples compared with those prepared by other methods. [ABSTRACT FROM AUTHOR]