New crystal structure in the BaO-Ce{sub 2}O{sub 3}-TiO{sub 2} system

Journal Article · Mon Dec 01 04:00:00 EST 1997 · Materials Research Bulletin

DOI:https://doi.org/10.1016/S0025-5408(97)00164-5· OSTI ID:586010

Rawn, C J; Makovec, D; Golic, L; Samardzija, Z; Kolar, D ^[1]

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1. Univ. of Ljubljana (Slovenia)

A new structure located in the TiO{sub 2}-rich corner of the BaO-Ce{sub 2}O{sub 3}-TiO{sub 2} system crystallizes with an orthorhombic unit cell, space group Pnma, and with lattice parameters a = 27.88(1), b = 7.745(2), and c = 17.350(4) {angstrom}. Refinement on F resulted in R1 = 6.46% for 3,868 F{sub o} > 4{sigma}. The structure is made up of a network of corner-sharing TiO{sub 6} octahedra creating rhombic (perovskite-like) and pentagonal channels. In this new structure, there are eight unique rhombic positions (occupied chiefly by Ce atoms), four unique pentagonal positions (occupied chiefly by Ba atoms), and eight unique Ti positions. Full occupation of the sites would correspond to the formula Ba{sub 16}Ce{sub 32}Ti{sub 64}O{sub 192}; however, refinement of the site occupancies of the Ce and Ba atoms suggests some substitution of the cations and vacancies. Electron probe wavelength dispersive spectroscopic microanalysis averaged from twenty measurements on three crystals results in 4.68 {+-} 0.11 at% Ba, 9.63 {+-} 0.30 at% Ce, and 18.57 {+-} 0.35 at% Ti.

• OSTI ID: 586010
• Journal Information: Materials Research Bulletin, Journal Name: Materials Research Bulletin Journal Issue: 12 Vol. 32; ISSN MRBUAC; ISSN 0025-5408
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BARIUM OXIDES
CERIUM OXIDES
CRYSTAL GROWTH
CRYSTAL STRUCTURE
TITANIUM OXIDES