ChemInform Abstract: Anisotropic Thermal Expansivity of Some Zircon-Type Rare Earth Arsenates.

ChemInform ◽  
1989 ◽  
Vol 20 (22) ◽  
Author(s):  
P. KISTAIAH ◽  
C. V. REDDY ◽  
K. S. MURTHY
Keyword(s):  
Rare Earth ◽  
Thermal Expansivity ◽  
Zircon Type

Anisotropic thermal expansivity of some zircon-type rare earth arsenates

1989 ◽  
Vol 147 (2) ◽  
pp. L35-L42 ◽  
Author(s):  
P. Kistaiah ◽  
C.Vishnuvardhan Reddy ◽  
K.Satyanarayana Murthy
Keyword(s):  
Rare Earth ◽  
Thermal Expansivity ◽  
Zircon Type

Kraftkonstanten des VO43- -Ions im Zirkon-Gitter [1] / Force Constants of the VO43- Ion in the Zircon Lattice

1980 ◽  
Vol 35 (10) ◽  
pp. 1110-1111 ◽  
Author(s):  
Marta E. Escobar ◽  
Enrique J. Baran
Keyword(s):  
Rare Earth ◽  
Raman Spectrum ◽  
Force Field ◽  
Force Constants ◽  
Tetragonal Modification ◽  
Valence Force ◽  
Valence Force Field ◽  
First Time ◽  
Rare Earth Orthovanadates ◽  
Zircon Type

Abstract Force Constants of the VO43- Ion in the different rare earth orthovanadates of the zircon type have been computed using a modified valence force field and recently reported Raman data. It is shown that the V-O bond strenghtening runs parallel to the unit cell contraction. The Raman spectrum of the tetragonal modification of LaVO4 is reported for the first time.

Magnesium-doped zircon-type rare-earth orthovanadates: Structural and electrical characterization

2018 ◽  
Vol 44 (1) ◽  
pp. 96-103
Author(s):  
T.H. Gayathri ◽  
A.A. Yaremchenko ◽  
J. Macías ◽  
P. Abhilash ◽  
S. Ananthakumar
Keyword(s):  
Rare Earth ◽  
Electrical Characterization ◽  
Rare Earth Orthovanadates ◽  
Zircon Type

scholarly journals Hydrothermal Alteration of Eudialyte-Hosted Critical Metal Deposits: Fluid Source and Implications for Deposit Grade

Minerals ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 422 ◽  
Author(s):  
Mathijs van de Ven ◽  
Anouk Borst ◽  
Gareth Davies ◽  
Emma Hunt ◽  
Adrian Finch
Keyword(s):  
Rare Earth ◽  
Hydrothermal Alteration ◽  
Nepheline Syenite ◽  
Partial Replacement ◽  
Magmatic Fluid ◽  
High Field Strength ◽  
Nd Isotope ◽  
Critical Metal ◽  
Rock Alteration ◽  
Zircon Type

Eudialyte-hosted critical metal deposits potentially represent major sources of rare earth elements (REE), zirconium and niobium. Here, we study the chemical and isotopic composition of fresh and altered eudialyte in nepheline syenite from the Ilímaussaq Complex, Greenland, one of the world’s largest known eudialyte-hosted deposits. Late-magmatic hydrothermal alteration caused partial replacement of primary magmatic eudialyte by complex pseudomorph assemblages of secondary Zr-, Nb-, and REE-minerals. Three secondary assemblage types are characterised by the zirconosilicates catapleiite, gittinsite and zircon, respectively, of which the catapleiite type is most common. To investigate elemental exchange associated with alteration and to constrain the nature of the metasomatic fluids, we compare trace elements and Sm/Nd isotope compositions of unaltered eudialyte crystals and their replaced counterparts from five syenite samples (three catapleiite-type, one gittinsite-type, and one zircon-type assemblage). Trace element budgets for the catapleiite-type pseudomorphs indicate a 15–30% loss of REE, Ta, Nb, Zr, Sr and Y relative to fresh eudialyte. Moreover, the gittinsite- and zircon-type assemblages record preferential heavy REE (HREE) depletion (≤50%), suggesting that the metasomatic fluids mobilised high field strength elements. Initial Nd isotope ratios of unaltered eudialyte and catapleiite- and gittinsite-type pseudomorphs are indistinguishable, confirming a magmatic fluid origin. However, a higher initial ratio and stronger HREE depletion in the zircon-type pseudomorphs suggests a different source for the zircon-forming fluid. Although alteration reduces the metal budget of the original eudialyte volume, we infer that these elements re-precipitate nearby in the same rock. Alteration, therefore, might have little effect on overall grade but preferentially separates heavy and light REE into different phases. Targeted processing of the alteration products may access individual rare earth families (heavy vs. light) and other metals (Zr, Nb, Ta) more effectively than processing the fresh rock.

Characterization of Rare-Earth Fluoride Anti-Stokes Phosphors by Scanning arid Transmission Electron Microscopy

1971 ◽  
Vol 29 ◽  
pp. 142-143
Author(s):  
N. M. P. Low ◽  
L. E. Brosselard
Keyword(s):  
Electron Microscopy ◽  
Rare Earth ◽  
Elevated Temperatures ◽  
Stoichiometric Composition ◽  
Rare Earth Ions ◽  
Crystalline Solid ◽  
Precipitation Process ◽  
Rare Earth Fluoride ◽  
Earth Fluoride ◽  
Rare Earth Fluorides

There has been considerable interest over the past several years in materials capable of converting infrared radiation to visible light by means of sequential excitation in two or more steps. Several rare-earth trifluorides (LaF3, YF3, GdF3, and LuF3) containing a small amount of other trivalent rare-earth ions (Yb3+ and Er3+, or Ho3+, or Tm3+) have been found to exhibit such phenomenon. The methods of preparation of these rare-earth fluorides in the crystalline solid form generally involve a co-precipitation process and a subsequent solid state reaction at elevated temperatures. This investigation was undertaken to examine the morphological features of both the precipitated and the thermally treated fluoride powders by both transmission and scanning electron microscopy.Rare-earth oxides of stoichiometric composition were dissolved in nitric acid and the mixed rare-earth fluoride was then coprecipitated out as fine granules by the addition of excess hydrofluoric acid. The precipitated rare-earth fluorides were washed with water, separated from the aqueous solution, and oven-dried.

Study of segregation in La1.8Sr0.2CuO4 superconductor by STEM-EDS microanalysis

1987 ◽  
Vol 45 ◽  
pp. 54-55
Author(s):  
T. F. Kelly ◽  
P. J. Lee ◽  
E. E. Hellstrom ◽  
D. C. Larbalestier
Keyword(s):  
Rare Earth ◽  
High Field ◽  
Transport Current ◽  
Total Thickness ◽  
New Class ◽  
Ceramic Superconductors ◽  
Current Densities ◽  
Group Ii ◽  
Eds Microanalysis

Recently there has been much excitement over a new class of high Tc (>30 K) ceramic superconductors of the form A1-xBxCuO4-x, where A is a rare earth and B is from Group II. Unfortunately these materials have only been able to support small transport current densities 1-10 A/cm2. It is very desirable to increase these values by 2 to 3 orders of magnitude for useful high field applications. The reason for these small transport currents is as yet unknown. Evidence has, however, been presented for superconducting clusters on a 50-100 nm scale and on a 1-3 μm scale. We therefore planned a detailed TEM and STEM microanalysis study in order to see whether any evidence for the clusters could be seen.A La1.8Sr0.2Cu04 pellet was cut into 1 mm thick slices from which 3 mm discs were cut. The discs were subsequently mechanically ground to 100 μm total thickness and dimpled to 20 μm thickness at the center.

Microstructural characterization of a cast RENi5-based alloy

1993 ◽  
Vol 51 ◽  
pp. 1176-1177
Author(s):  
G. M. Micha ◽  
L. Zhang
Keyword(s):  
Electron Microscopy ◽  
Rare Earth ◽  
Microstructural Characterization ◽  
Binary Compound ◽  
Nickel Metal ◽  
Cast Material ◽  
Nickel Metal Hydride ◽  
Transmission Electron ◽  
Cast Condition

RENi5 (RE: rare earth) based alloys have been extensively evaluated for use as an electrode material for nickel-metal hydride batteries. A variety of alloys have been developed from the prototype intermetallic compound LaNi5. The use of mischmetal as a source of rare earth combined with transition metal and Al substitutions for Ni has caused the evolution of the alloy from a binary compound to one containing eight or more elements. This study evaluated the microstructural features of a complex commercial RENi5 based alloy using scanning and transmission electron microscopy.The alloy was evaluated in the as-cast condition. Its chemistry in at. pct. determined by bulk techniques was 12.1 La, 3.2 Ce, 1.5 Pr, 4.9 Nd, 50.2 Ni, 10.4 Co, 5.3 Mn and 2.0 Al. The as-cast material was of low strength, very brittle and contained a multitude of internal cracks. TEM foils could only be prepared by first embedding pieces of the alloy in epoxy.

Rare Earth Production

1952 ◽  
Vol 44 (3) ◽  
pp. 442-442
Author(s):  
Frank Spedding ◽  
Harley Wilhelm ◽  
Wayne Keller et al
Keyword(s):  
Rare Earth
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