Structural characterization and Curie temperature determination of a sodium strontium niobate ferroelectric nanostructured powder

• Published in: Journal of solid state chemistry 2011-05, Vol.184 (5), p.990-1000
• Main Authors: Lanfredi, Silvania, Gênova, Diego H.M., Brito, Iara A.O., Lima, Alan R.F., Nobre, Marcos A.L.
• Format: Article
• Language: English
• Subjects: ABSORPTION SPECTROSCOPY; ALLOYS; CATIONS; CHARGED PARTICLES; Condensed matter: electronic structure, electrical, magnetic, and optical properties; COPPER ALLOYS; COPPER BASE ALLOYS; Correlation; Cross-disciplinary physics: materials science; rheology; Crystallites; CRYSTALLOGRAPHY; CURIE POINT; Curie temperature; DIELECTRIC MATERIALS; Dielectric, piezoelectric, ferroelectric and antiferroelectric materials; Dielectrics, piezoelectrics, and ferroelectrics and their properties; DISTANCE; Exact sciences and technology; Ferroelectric; FERROELECTRIC MATERIALS; Ferroelectricity and antiferroelectricity; IMPEDANCE; Impedance spectroscopy; INFRARED SPECTRA; Infrared spectroscopy; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; INTERATOMIC DISTANCES; IONS; MATERIALS; Materials science; Nanopowders; Nanoscale materials and structures: fabrication and characterization; Nanostructure; Nanostructured powder; NANOSTRUCTURES; NIOBATES; Niobium; NIOBIUM COMPOUNDS; NIOBIUM IONS; OXYGEN COMPOUNDS; Phase transitions and curie point; PHYSICAL PROPERTIES; Physics; POLARIZATION; POWDERS; REFRACTORY METAL COMPOUNDS; Rietveld method; Roasting; Sodium; SODIUM IONS; SPECTRA; SPECTROSCOPY; STRONTIUM IONS; TEMPERATURE RANGE; TEMPERATURE RANGE 1000-4000 K; THERMODYNAMIC PROPERTIES; TRANSITION ELEMENT ALLOYS; TRANSITION ELEMENT COMPOUNDS; TRANSITION TEMPERATURE; TUNGSTEN ALLOYS; TUNGSTEN BRONZE
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1016/j.jssc.2011.03.001

The Curie temperature and its correlation with the magnitude of the displacement of the niobium atom from the center of [NbO 6] octahedra in NaSr 2Nb 5O 15 nanostructured powder were investigated. A single powder was prepared by high-energy ball milling. A powder with an average crystallite size of 37 nm was prepared by calcining the precursor at 1423 K. The refinement of the structural parameters was carried out by the Rietveld method. NaSr 2Nb 5O 15 exhibits tetragonal symmetry with the tungsten bronze structure ( a= b=12.3495 (6) Å, c=3.8911 (2) Å, V=593.432 (5) Å 3, and Z=2). The site occupancy of the Na + and Sr 2+ cations and the interatomic distances between the niobium and oxygen atoms were derived. The [NbO 6] octahedron undergoes both rotation and tilting depending on the crystallographic site. The Curie temperature of the powder was derived using both the impedance and infrared spectroscopy methods. Representation of the unit cell of the NaSr2Nb5O15 powder. Nb 5+ cations are differentiated as Nb(I) and Nb(II). [Nb(I)O6] octahedral sites are represented by yellow color and [Nb(II)O6] by blue ones [Display omitted] . ► Spontaneous polarization has been based on the off-center displacement of atoms. ► Distortion of the [Nb(II)O 6] octahedra occurs due to both to [NbO 6] octahedron rotation and tilting. ► Newest another equation to derive the parameter Curie's temperature. ► The ferroelectric transition in the NaSr 2NaNb 5O 15 powder is of displacive type.