The flux growth of some rare-earth and iron group complex oxides

The flux growth of crystals of the following rare-earth complex oxides is reported here for the first time: (Nd, Pb)MnO₃, (Eu, Pb)MnO₃. Tm₂Ge₂O₇ and Pr₂MoO₆. Starting compositions for the flux growth of RBO₃ (R=Nd, Pr, La), (La, Pb)MnO₃, Pb₃Mn₇O₁₅, R₂Ti₂O₇ (R=Tm to Pr), R₂SiO₅ (R=Er, Ho, Dy) and LiCoPO₄ are also given; these compositions have yielded larger crystals than previously reported. In many cases, only a small number of crystals was obtained by spontaneous nucleation.     

The flux growth of rare earth germanomolybdates and germanotungstates

The growth of R₂GeMoO₈ and R₂GeWO₈ crystals from the flux systems R₂O₃-GeO₂-MO₃-PbO, where M = Mo or W, is described. A preliminary investigation of their magnetic properties is reported. The X-ray powder pattern data for R₂GeWO₈ with R = Gd, Tb, Dy, Ho and Er are given.     

Crystal growth of some rare earth trifluorides

Single crystals of GdF₃, TbF₃, DyF₃, HoF₃ and ErF₃ have been grown by using a Bridgman-Stockbarger method utilising sealed platinum crucibles. DyF₃ and HoF₃ have also been grown by the Czochralski technique.     

Optical properties of zirconia doped with yttria and some rare earth oxides

Nanometric powders of cubic zirconia stabilized with yttria and rare element oxides (Sm, Nd, Gd) were prepared by crystallization under hydrothermal conditions. The powders were uniaxially compacted, repressed isostatically, pressure-less sintered in oxygen atmosphere and hot isostatically pressed under 300 MPa Ar atmosphere. Fully dense samples were polished from both sides. The optical properties were analyzed based on the spectral dependence of the transmittance (T) and reflectance (R). Spectroscopic measurements have shown that all materials fabricated in the present work are highly transparent, with total transmission above 90% towards the long-wavelength end of the near-IR range of the spectrum. Discussion of these results will be given.     

Investigation of infrared absorption spectra of copper phosphate glasses containing some rare earth oxides

The spectra of copper-lutetium-phosphate and copper-erbium-phosphate glasses have been studied within the spectral range 4000 to 400 cm^– by Fourier transform infrared spectroscopy. Incorporation of a small amount of lutetium or erbium influences some band positions compared with binary copper phosphate glasses. The additional bands in the range 491 to 576 cm^–1 are attributed to the presence of Lu-O and Er-O groups. It has been observed that annealing of the samples at 500 ° C leads to a slight shift in the peak positions.     

An electron spin resonance study of copper phosphate glasses containing some rare earth oxides

The electron spin resonance spectra of phosphate glasses containing mixed Cu²⁺-Er³⁺ and Cu²⁺-Lu³⁺ oxides have been examined. A reduction in the copper (II) signal intensity in the glasses as the proportion of rare earth oxide is raised corresponds to an increase in the reduced valency ratio C in the glasses. Differences between the behaviour of glasses containing erbium and those containing lutetium are observed and probably arise from magnetic coupling between copper (II) and erbium (III).     

Synthesis of nanocrystalline rare earth oxides by glycothermal method

The reaction of yttrium acetate hydrate in 1,2-propanediol at 300 °C yielded a product containing acetate groups and glycol moieties. From this product, Y₂O₃ was directly crystallized at 400 °C without the formation of a carbonate oxide phase. The thus-obtained Y₂O₃ samples had a small crystallite size (2.2 nm) and significantly large surface area (280 m²/g). Other nanocrystalline rare earth (Gd-Yb) oxides were also obtained by this method.     

Structural and magnetic investigations of some new boron containing rare earth intermetallic compounds

By alloying boron with RPd₃ (R=rare earth) compounds, new ternary alloys of the formula RPd₃B _x (0 ≤x ≤ 1) have been prepared. The parent RPd₃ compounds crystallise in the cubic AuCu₃ type structure. The addition of boron does not change the structure but results in an expansion of the lattice. Therefore, it is likely that the small boron atoms occupy the vacant body centred position in AuCu₃ type structure. It is also observed that compounds of the composition RRh₃B can be formed in the cubic structure for all rare earths R though the parent RRh₃ compounds exist only for R=Ce (AuCu₃ type) and La, Sm, Nd and Gd (all hexagonal CeNi₃ type). This points out the role of boron in stabilising new crystallographic phases. The results of susceptibility measurements on some of the RPd₃B and RRh₃B compounds are presented. In particular, it is noted that while GdPd₃ orders antiferromagnetically withT _N=6 K, GdPd₃B does not order magnetically down to 4.2 K.     

A novel non-Pb flux system for the preparation of yttrium and rare earth iron gallium and aluminum garnets

A flux composed of lithium and rare earth molybdates has been found to be an effective transfer medium for the preparation of yttrium and rare earth iron gallium and aluminum garnets. Magnetic bubble domain properties of epitaxial iron garnet films grown from the molybdate flux are easily controlled by virtue of the transfer process including dimensional control for submicron thick films. The properties of these films compare well to those grown from the PbO·B₂O₃ flux, but the films are contaminant free. This is particularly important for the growth of Nd-doped YAG laser films. Stability region of the garnet phase in the Li₂MoO₄Y₂O₃MoO₃ pseudo-ternary system and solubility are discussed as related to crystal and film growth.     

Perovskite-like rare earth gallium oxides prepared at atmospheric pressure

The rare earth gallium oxide perovskites, RGaO₃, RSmEr, have been synthesized at $\text{normal}$ pressure, quenched from temperatures exceeding 1650°C. Lattice constants of these and of newly prepared LaGaO₃, PrGaO₃ and NdGaO₃ by solid state reaction have been measured. The $\text{c}$ and $\text{a}$ vs. atomic number plots are characteristic of the lanthanon contraction with cusps at gadolinium.     

Magnetic properties of some rare earth ferrites

The tetragonal SrEu₂Fe₂O₇ and BaEu₂Fe₂O₇ have been investigated using Mössbauer spectroscopy and magnetic susceptibility techniques. The measurements of magnetic susceptibility have been carried out in the temperature range 100 to 700°K. The data have been fitted to Curie-Weiss law $\text{χ =}\text{C}\text{T}\text{+ θ +}\text{A}$ using a non-linear least square curve fitting procedure. These ferrite compounds are paramagnetic above 534°K and 537°K respectively, with antiferromagnetic ordering below these temperatures.     

Flux growth of rare earth silicates and aluminosilicates

Crystals of R₂SiO₅, R₂Si₂O₇, rare earth apatites, and square-faceted rare earth aluminium garnets containing silicon have been grown from fluxed melts. Silicon was provided in two ways: by vapour transport of a siliceous vapour species which diffused into the melts (vapour-flux method), and by including SiO₂ in the initial mixtures. The results of these two methods are compared.The materials have been characterized by X-ray diffraction and, in some cases, by EPMA. Powder pattern data for some of the rare earth apatites are included.     

稀土掺杂的Ba1-xSrxTiO3/MgO材料性能的影响

主要研究了La2O3、Sm2O3、Dy2O3、CeO2等稀土氧化物掺杂的BSTO/MgO铁电移相器材料的调谐性T、低频(10kHz)与高频(2GHz左右)相对介电常数εr和介质损耗tgδ等性能,并对影响机理作了初步探讨.实验结果表明,0.5mol%La2O3掺加的BSTO/MgO系统基本上达到了相控阵移相器在高频下工作的要求10kHz下,tgδ=4×10-4,T=14.6%;2.41GHz下,tgδ=6.7×10-3.     

Physical properties of some rare earth tellurite glasses

Mossbauer and IR spectra as well as the electrical conductivity have been measured to give an idea about the structure and the electrical properties of some rare earth tellurite glasses containing Fe₂O₃. The glasses denoted [1 – (2x + 0.05)] TeO₂ ·xFe₂O₃ · (x + 0.05) Ln₂O₃, wherex = 0.0 and 0.05 and Ln = lanthanum, neodymium, samarium, europium or gadolinium, were prepared by fusing a mixture of their respective reagent grade oxides in a platinum crucible at 800° C for one hour. The Mossbauer parameters such as isomer shift, quadruple splitting and line width were found to be a function of the polarizing power (charge/radius) of the rare earth cations. The Mossbauer parameters were not affected by the heat treatment of the glass samples. Both of the Te-O-Ln and Te-O-Fe stretching vibrations were obtained from the IR results which indicate that the rare earth oxides and iron oxide are partially covalent. The electrical resistivity was measured as a function of temperature from 293 to 520 K. Both the electrical resistivity and the activation energy were found to be a function of the atomic number (Z) of the rare earth cations. The results were interpreted on the basis of the electronic structure of the glass.