Ionic Radius Of RE3 Research Articles

RE-123 thin films for microwave applications

Large area REBa 2Cu 3O 7 (RE-123; RE=rare earth) thin films have been grown by reactive thermal coevaporation. The work was targeted to identify compounds with superior high frequency properties compared to Y-123 films. As a general trend we found that with increasing RE ionic radius the transition temperature as well as the tendency for cracking increased. No such trend was recognizable for the surface resistance. Dy-123 and Nd-123 films exhibit lower surface resistance at 77 K than Y-123 films at the same thickness. On sapphire substrates however Y-123 films are advantageous because they are less susceptible to thermal cracking.

Electrical properties of (Bi 2O 3) 0.75(RE 2O 3) 0.25 ceramics (RE=Dy, Y, Ho, Er and Yb)

Five kinds of rare earth stabilized bismuth oxide ceramics, (Bi 2O 3) 0.75(RE 2O 3) 0.25 (RE=Dy, Y, Ho, Er and Yb), were synthesized by sintering a mixture of Bi 2O 3 and RE 2O 3 at 900–1100 °C and their electrical properties were investigated. The bulk density and the lattice constant linearly increased with an increase in the atomic weight of RE and the ionic radius of RE 3+, respectively. The electrical conductivity at 300 °C slightly increased with the increasing ionic radius of RE 3+, while at 500 and 700 °C, it was constant regardless of the ionic radius of RE 3+. The migration activation energy and the association activation energy showed a maximum value and a minimum value at RE=Er, respectively.

Consequence of isovalent rare earth substitution to magnetic irreversibility in cation-stoichiometric CuBa2RECu2O6.93±0.01

For a series of CuBa2RECu2O7−δ (Cu−1(Ba)2RE12; RE= rare earth element) single-phase cation-stoichiometric samples with a fixed oxygen content, δ=0.07±0.01, a clear dependence of the Hirr characteristics on the ionic radius of RE is revealed. With decreasing ionic radius of RE, the Hirr characteristics are remarkably enhanced such that the samples containing heavy REs exhibit very high Hirr values. This result implies that through isovalent cation substitution alone carrier-density distribution and thereby the superconductivity characteristics may be controlled.

Thermally Decomposed Products of Heteronuclear Complexes, CuRE(dhbaen)(NO3)(dmso)m(H2O)n, (RE=Sm, Eu, Gd, Tb, Dy, Y, Ho, Er, Tm, Tb, and Lu).

The thermally decomposed products of the CuRE(dhbaen)(NO3)(dmso)m(H2O)n complex were investigated by differential thermal analysis (TGA), X-ray diffraction patterns (XRD), energy dispersive X-ray analysis (EDX), and X-ray photoelectron spectroscopy (XPS). A mixed phase of RE2O2SO4 and CuO was formed at a low temperature. The particle size of CuO in the mixed phase was estimated to be 30-90nm by XRD. When the ionic radius of RE3+ ion is small, the RE2O2SO4 phase decomposed and formed a heterometallic RE2Cu2O5 at 850-1100°C. It appears that one dmso directly interacted with the RE ion (RE-O=S(-CH3)2) for the complex and the RE-O=S bond remained as RE2O2SO4 after the decomposition. CuO in the mixed phase did not interact with -SO4 which was confirmed by XPS.

Nature of spin freezing transition of geometrically frustrated pyrochlore system R 2Ru 2O 7 (R=rare earth elements and Y)

At the spin-glass-like transition of yttrium ruthenium pyrochlore system Y 2Ru 2O 7, a significant jump of the specific heat has been found, suggesting the second order-like nature of the transition. It is commonly observed for other pyrochlore systems R 2Ru 2O 7 (R=various rare earth elements RE). For all REs studied here, the transition temperature T G is larger for the larger R-ions, which may be due to the increase of the transfer energies of the 4 d electrons between the neighboring Ru atoms with increasing RE ionic radius. Neutron Rietveld analyses on Y 2Ru 2O 7 and Nd 2Ru 2O 7 have revealed that below T G, the Ru spins are in an almost long-range ordered antiferromagnetic state, though it is magnetically glassy in a macroscopic sense, and that the lattice system does not participate in the transition. It is concluded that the specific heat jump is created by the purely magnetic origin.

Synthesis of Na2O-RE2O3-SiO2(RE=Sm,Gd,Dy,Y,Ho,Er and Yb) System Glasses and Their Electrical Properties.

Seven kinds of sodium rare-earth silicate glass, (Na2O)35.7(RE2O3)7.2(SiO2)57.1 (RE=Sm, Gd, Dy, Y, Ho, Er and Yb), were synthesized by melting a mixture of Na2CO3, RE2O3 and SiO2 and their electrical properties were investigated. The densities of glasses were in fairly good agreement with the theoretical densities predicated for Na5RESi4O12 ceramics. The crystallization temperature and the crystal melting temperature linearly decreased with increasing the ionic radius of RE. The highest electrical conductivity at 200°C (1.55×10-4S·cm-1) was achieved for (Na2O)35.7(Yb2O3)7.2(SiO2)57.1. The electrical conductivity slightly decreased with increasing the ionic radius of RE.

Dielectric properties of LiF-B2O3 glasses doped with certain rare earth ions

Dielectric constantɛ, loss tanδ and a.c. conductivityσ of LiF-B2O3: Ln3+ (where Ln=Ce, Pr, Nd and Tb) glasses are studied as functions of frequency (in the range 102–106 Hz) and temperature (range 30–200°C). The dielectric breakdown strength of these glasses was also determined at room temperature in an air medium. The rate of increase ofɛ and tanδ with temperature decreases with decrease in the ionic radius of RE3+ ion whereas the dielectric breakdown strength, the activation energy for a.c. conduction in the high temperature region decreases with increase in the ionic radius of RE3+ ion. An attempt has been made to explain the a.c. conduction in these glasses on the basis of quantum mechanical tunnelling (QMT) model.

Conditions and Possibilities for Rare-Earth Doping of KTiOPO4 Flux-Grown Single Crystals

The growth of rare-earth (RE = Nd, Tb, Ho, Er, Tm, and Yb) doped KTiOPO4 (KTP) single crystals from high-temperature solutions [K2O−P2O5−TiO2−RE2O3 (or Tb4O7)] was investigated. The concentration regions of crystallization of RE-doped KTP, the maximum (critical) RE concentrations in the solution without losing the KTP phase and the corresponding upper limit of RE ions incorporated into the KTP lattice were obtained experimentally. The crystallization regions of RE-doped KTP are significantly narrower than the region of undoped KTP. Above a certain critical RE concentration in the solution, RE phosphate phases crystallize. The highest concentration of RE in the crystal is in the range 50−600 ppm and strongly depends on the RE ionic radius. Some double substitutions with Nd and a codopant element can significantly change this concentration. In addition, RE-doped KTP single crystals were grown by the top seeded solution growth (TSSG) technique, and their experimental conditions were compared with those of undoped KTP single-crystal growth. Optical absorption spectra for Ho-, Er-, and Tm-doped KTP were obtained and discussed.

Influence of the size of RE 3+ ions on the stability of new perovskite-like phases in the most basic region of the systems BaRECuO ( RE ≡ Ln, Y)

The influence of size of the ionic radius of RE 3+ ions ( RE ≡ La, Nd, Sm, Gd, Dy, Ho, Yb, Y) on the formation of the different and mutually exclusive phases Ba 2 − x RE x CuO 3 + δ, or Ba 4RECu 3O 9 and Ba 6RECu 3O 11 in the BaO rich zones of the BaRECuO systems was examined. The structures of the different phases were characterized by X-ray diffraction and their derivation from formerly examined phases of perovskite or layered perovskite type was examined. The importance of the preparation method used is stressed, in particular the exclusion of traces of CO 3 2− and CO 2 from the starting materials and from the gaseous atmosphere.

Les differentes formes cristallines de Y 3ReO 8: Relations avec la structure fluorine

The monoclinic Y 3ReO 8β phase is synthetized at 40 kbar and 900°C. The crystal structure is solved to an R value of 0.058 for 1341 observed reflections, by conventional methods using automated four-circle diffractometer data. This structure can be visualized as a fluorite-related superstructure, the large difference between the ionic radii of Re 7+ and Y 3+ being favorable to cation ordering. The heating to 500°C of this phase under atmospheric pressure leads to a disordered fluorite structure of the form Y 3ReO 8α. An intermediary metastable phase Y 3ReO 8α′ is obtained by heating a Y 3ReO 8β single crystal to 350°C. The structural relations between these three crystalline forms of Y 3ReO 8 and the fluorite structure are discussed.