An X-ray powder and electron diffraction study of reduced tantalates with the perovskite structure, Na1-xSrxTaO3, 0 < x <= 0.4
2000 (English)In: Journal of Solid State Chemistry, ISSN 0022-4596, E-ISSN 1095-726X, Vol. 154, 427-434 p.Article in journal (Refereed) Published
Single-phase perovskite-type reduced tantalates, Na1-x SrxTaO3 with 0 < x 0.4, have been synthesized by heating mixtures of NaTaO3, Sr5Ta4O15 and Ta in sealed tantalum ampules at 1400 degreesC for 20-24 h. At Sr contents of 0.5 less than or equal to x less than or equal to 0.8 and above 1400 degreesC, polyphasic samples were obtained. X-ray powder diffraction (XRD) and transmission electron microscopy studies (selected area (SAED) and convergent beam electron diffraction (CBED)) showed an orthorhombic distortion of the x = 0.1 sample (GdFeO3 type, space group Pnma). The interpretation of the XRD, SAED, and CBED studies indicates the crystallites found in the x = 0.2 and 0.3 samples to consist of domains with tetragonal and orthorhombic symmetry having the unit Cell parameters of a = b approximate to root (2a(per)) and c approximate to 2a(per) and a approximate to b approximate to root (2a(per)) and c approximate to a(per) (a(per) cell axis in the ideal perovskite structure), respectively. The x 0.4 sample was cubic (space group Pm3m) with a = a(per). Resistivity measurements showed that all samples are semiconducting and that the conductivity increases with Sr content. Magnetic measurements of Na0.6Sr0.4TaO3 revealed a diamagnetic behavior down to 20 K. Below this temperature a slight paramagnetism arises. (C) 2000 Academic Press.
Place, publisher, year, edition, pages
2000. Vol. 154, 427-434 p.
reduced oxotantalate, perovskite, electron diffraction, crystal structure, X-ray powder diffraction
Research subject Inorganic Chemistry
IdentifiersURN: urn:nbn:se:su:diva-43878DOI: 10.1006/jssc.2000.8860OAI: oai:DiVA.org:su-43878DiVA: diva2:371576