Cubic Perovskite (cubic + perovskite)

Distribution by Scientific Domains

Terms modified by Cubic Perovskite

  • cubic perovskite structure

  • Selected Abstracts

    Phase relations in the Ba,Sr,Co,Fe,O system at 1273,K in air

    Zhn Yng
    Selected compositions of the Ba,Sr,Co,Fe,O system were synthesized from powders by the solid-state reaction method. Samples were equilibrated at 1273,K for 36,000,s in air. The resulting powders were characterized by X-ray diffraction (XRD) at room temperature and by high-temperature in situ XRD. The phases present in the BaxSr1,xCoyFe1,yO3,, system are outlined for 1273,K in air. For most of the quaternary compositions, the cubic perovskite is formed, except for the compositions with x = 1 (excluding y = 0.4), y = 1 and x, y = 0.8, where the phases mainly show hexagonal distortions, and x, y = 0, for which a predominant cubic phase is mixed with other phases. [source]

    Performance of a new furnace for high-resolution synchrotron powder diffraction up to 1900,K: application to determine electron density distribution of the cubic CaTiO3 perovskite at 1674,K

    Masatomo Yashima
    Accurate crystal structure analysis at high temperatures is an important challenge in science and technology. A new electric furnace for the measurement of high-resolution (,d/d = 0.03%) synchrotron radiation powder diffraction profiles from materials at high temperatures (up to 1900,K in air) has been designed and fabricated. This furnace consists of a ceramic refractory with MoSi2 heaters, an aluminium body cooled by flowing water, and a sample stage with a spinner and a controller for sample-height adjustment. In situ synchrotron powder diffraction measurement for a calcium titanate perovskite specimen at 1674,K has been performed using the furnace at beamline 3A of the Photon Factory. The electron density distribution of the cubic perovskite at 1674,K was successfully obtained using a combination of Rietveld refinement, the maximum-entropy method (MEM) and MEM-based pattern-fitting techniques. The Ti atoms exhibit covalent bonding with the O atoms in the cubic CaTiO3 perovskite at this temperature, while the Ca atoms are ionic. These results indicate that the new furnace yields high-quality data for accurate crystal structure analysis. [source]

    Barium Holmium Zirconate, A New Perovskite Oxide: II, Synthesis as Nanoparticles through a Modified Combustion Process

    Rajan Jose
    Nanoparticles of barium holmium zirconate, a new complex perovskite ceramic oxide, has been synthesized using a modified self-propagating combustion process. The solid combustion products obtained were characterized by X-ray diffraction (XRD), electron diffraction, differential thermal analysis, thermogravimetric analysis, infrared spectroscopy, particle size analysis, surface area determination, and high-resolution transmission electron microscopy. The XRD and electron diffraction studies have shown that the as-prepared powder is phase pure Ba2HoZrO5.5 and has a complex cubic perovskite (A2BB,O6) structure with a lattice constant a= 8.428 . The transmission electron microscopic investigation has shown that the particle size of the as-prepared powder was in the range 4,16 nm with a mean grain size of 8.2 nm. The nanoparticles of Ba2HoZrO5.5 obtained by the present method could be sintered to 98% theoretical density at 1500C. [source]

    Structural stability and formability of ABO3 -type perovskite compounds

    Huan Zhang
    On the basis of the bond-valence model (BVM) and structure-map technology, the structural stability and formability of ABO3 -type perovskite compounds were investigated in 376 ABO3 -type compounds. A new criterion of structural stability for ABO3 -type perovskite compounds has been established by the bond-valence calculated tolerance factors, which are in the range 0.822,1.139. All global instability indices for ABO3 -type perovskite compounds are found to be less than 1.2,v.u. (valence units) and increase with a decrease in oxidation state of the B cations (i.e. structural stability in the formation of an ideal cubic perovskite follows the order A+B5+O3 -type > A2+B4+O3 -type > A3+B3+O3 -type). Three new two-dimensional structure maps were constructed based on the ideal A,O and B,O bond distances derived from the BVM. These maps indicate the likelihood of particular perovskite compounds being formed. The present work enables novel perovskite and perovskite-related compounds to be explored by screening all the possible elemental combinations in future crystal engineering. [source]

    Al14Ba8La26.3Ru18Sr53.7O167: a variant of cubic perovskite with isolated RuO6 units

    F. J. Ziga
    The crystal structure of the title aluminium barium lanthanum ruthenium strontium oxide has been solved and refined using neutron powder diffraction to establish the parameters of the oxygen sublattice and then single-crystal X-ray diffraction data for the final refinement. The structure is a cubic modification of the perovskite ABO3 structure type. The refined composition is Ba0.167La0.548Sr1.118Ru0.377Al0.290O3.480, and with respect to the basic perovskite structure type it might be written as (Ba8La13.68Sr34.32)(Al13.92La12.64Ru18.08Sr19.36)O192,x, with x = 24.96. The metal atoms lie on special positions. The A -type sites are occupied by Ba, La and Sr. The Ba atoms are located in a regular cuboctahedral environment, whereas the La and Sr atoms share the same positions with an irregular coordination of O atoms. The B -type sites are divided between two different Wyckoff positions occupied by Ru/Al and La/Sr. Only Al and Ru occupy sites close to the ideal perovskite positions, while La and Sr move away from these positions toward the (111) planes with high Al content. The structure contains isolated RuO6 octahedra, which form tetrahedral substructural units. [source]