Synthesis and characterization of reduced niobates CaLnNb2O7, Ln = Y, Nd with a pyrochlore structure
1997 (English)In: Materials research bulletin, ISSN 0025-5408, E-ISSN 1873-4227, Vol. 32, no 4, 421-430 p.Article in journal (Refereed) Published
The first known reduced niobates with a pyrochlore structure, CaLnNb(2)O(7) Ln = Y, Nd, have been synthesized from Ca2Nb2O7, Ln(2)O(3), and NbO2 in sealed Nb ampoules heated at 1400 degrees C for 6 h. Our studies show that these compounds have a small homogeneity region according to the formula Ca(2-x)Ln(x)Nb(2)O(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 CaNdNb2O7 and CaYNb2O7 were refined using X-ray and neutron powder diffraction data. CaNdNb2O7 and CaYNb2O7 have undistorted pyrochlore structures: space group Fd3m, a = 10.416(1) Angstrom and 10.3159(8) Angstrom, respectively. Resistivity measurements show that CaNdNb2O7 exhibits semiconducting behavior. Copyright (C) 1997 Elsevier Science Ltd.
Place, publisher, year, edition, pages
1997. Vol. 32, no 4, 421-430 p.
oxides, chemical synthesis, X-ray diffraction, crystal structure, electric properties
IdentifiersURN: urn:nbn:se:su:diva-43895DOI: 10.1016/S0025-5408(96)00003-7OAI: oai:DiVA.org:su-43895DiVA: diva2:371121