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Hydrothermal synthesis, structure, and magnetic properties of a new polymorph of lithium vanadyl(IV) orthophosphate: β-LiVOPO4

Authors
Journal
Journal of Solid State Chemistry
0022-4596
Publisher
Elsevier
Publication Date
Volume
95
Issue
2
Identifiers
DOI: 10.1016/0022-4596(91)90116-y
Disciplines
  • Earth Science
  • Geography
  • Physics

Abstract

Abstract A new polymorph of lithium vanadyl(IV) orthophosphate, β-LiVOPO 4, has been synthesized hydrothermally in a sealed quartz glass tube under autogeneous pressure by slowly cooling from 450°C a mixture of Li 2O, VO 2, and 7.25 M H 3PO 4. This metastable compound has been characterized through a combination of techniques including single-crystal X-ray diffraction, differential thermal analysis, electron paramagnetic resonance, and magnetic susceptibility measurements. It crystallizes in the orthorhombic space group Pnma with a = 7.444(2), b = 6.300(1), c = 7.174(2) A ̊ , V = 336.4(2) A ̊ 3, Z = 4 , and R = 0.0248. Its framework consists of infinite chains of corner-shared VO 6 octahedra, parallel to the a-axis, cross-linked by corner-shared PO 4 tetrahedra. These infinite chains have alternating short and long VO bonds and are similar to those found in β-VOPO 4. The Li atom has six close oxygen neighbors. The β → α-LiVOPO 4 phase transition is reconstructive and occurs at ∼750°C. The magnetic susceptibility is analyzed considering the expression of Bonner and Fisher for S = 1 2 ions isotropically coupled in antiferromagnetic linear chains.

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