Crystal structure of La(Mg2/3M1/3)O3 (M=Nb,Ta) microwave dielectric ceramics

Jeong Seog Kim, Chae Il Cheon, Hyun Ju Kang, Hae Seop Shim, Chang Hee Lee, Sahn Nam, Jae Dong Byun

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)

Abstract

Crystal structure of (Ba1-xLax)(Mg(1+x)/3Nb(2-x)/3)O 3 (0.5≤x≤1.0) and La(Mg2/3Ta1/3)O3 microwave dielectric ceramics were analysed by the Rietveld refinement method using X-ray and neutron powder diffraction data. In the composition range 0.5≤x≤0.07, the 1:1 ordered cubic structure (Fm3̄m) is maintained. The end members, La(Mg2/3Nb1/3)O3 and La(Mg2/3Ta1/3)O3, are most successfully refined using an orthorhombic structure Pbnm (a≈5.61, b≈5.64, c≈7.95 Å) contrary to the expectations of earlier works which suggested an 1:1 ordered rhombohedral or monoclinic structure. The structure is similar to CaTiO3 having oxygen-octahedron tilting and La-displacements. The small ionic size of La+3 and hence a small tolerance factor (t≈0.92) is responsible for the orthorhombic distortion. No long-range order of B-site cations exists.

Original languageEnglish
Pages (from-to)294-299
Number of pages6
JournalMaterials Letters
Volume38
Issue number4
DOIs
Publication statusPublished - 1999 Feb

Keywords

  • 77.84.Dy
  • 77.90.+k
  • B-site disorder
  • Crystal structure
  • La(MgNb)O
  • Microwave dielectrics
  • Orthorhombic Pbnm
  • Rietveld refinement
  • Space-group
  • X-ray and neutron diffraction

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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