Synthesis and characterization of reduced niobates CaLnNb{sub 2}O{sub 7}, Ln = Y, Nd with a pyrochlore structure

Journal Article · Tue Apr 01 04:00:00 EST 1997 · Materials Research Bulletin

DOI:https://doi.org/10.1016/S0025-5408(96)00003-7· OSTI ID:484865

Istomin, S Ya; D`yachenko, O G; Antipov, E V ^[1]; Svensson, G ^[2]

---

1. Moscow State Univ. (Russian Federation). Dept. of Chemistry
2. Stockholm Univ. (Sweden). Arrhenius Lab.

The first known reduced niobates with a pyrochlore structure, CaLnNb{sub 2}O{sub 7} Ln = Y, Nd, have been synthesized from Ca{sub 2}Nb{sub 2}O{sub 7}, Ln{sub 2}O{sub 3}, and NbO{sub 2} in sealed Nb ampoules heated at 1,400 C for 6 h. Their studies show that these compounds have a small homogeneity region according to the formula Ca{sub 2{minus}x}Ln{sub x}Nb{sub 2}O{sub 7}, Ln = Nd with x = 0.9, 1.0; and Ln = Y with x = 1.0, 1.1. The prepared compounds were characterized by EDX (energy dispersive X-ray) analysis, X-ray and electron diffraction, and thermogravimetric analysis. The crystal structures of CaNdNb{sub 2}O{sub 7} and CaYNb{sub 2}O{sub 7} were refined using X-ray and neutron powder diffraction data. CaNdNb{sub 2}O{sub 7} and CaYNb{sub 2}O{sub 7} have undistorted pyrochlore structures: space group Fd3m, a = 10.416(1) A and 10.3159(8) A, respectively. Resistivity measurements show that CaNdNb{sub 2}O{sub 7} exhibits semiconducting behavior.

• OSTI ID: 484865
• Journal Information: Materials Research Bulletin, Journal Name: Materials Research Bulletin Journal Issue: 4 Vol. 32; ISSN MRBUAC; ISSN 0025-5408
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CALCIUM OXIDES
CRYSTAL STRUCTURE
ELECTRIC CONDUCTIVITY
EXPERIMENTAL DATA
NEODYMIUM OXIDES
NEUTRON DIFFRACTION
NIOBIUM OXIDES
STOICHIOMETRY
SYNTHESIS
X-RAY DIFFRACTION
YTTRIUM OXIDES