Structure and Physical Properties of La3.4Ca0.6V5Si4O22: A Novel Mixed-Valent Vanadium(III/IV) Oxosilicate

S. C. Chen, K. V. Ramanujachary, M. Greenblatt

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Abstract

La3.4Ca0.6V5Si4O22 crystallizes in the monoclinic system, space group C2/m (No. 12). The unit cell dimensions are a = 13.448(4) Å,b = 5.5879(9) Å, c = 11.070(4) Å, β = 100.57(2)°, V = 817.7(4) Å3 123, and Z = 2. Structural refinement with 817 observed reflections (I > 3 σ(I)) and 103 variable parameters resulted in R = 0.034, Rw = 0.037. The structure of La3.4Ca0.6V5Si4O22 may be described as the intergrowth of vanadium pyrosilicate layers, VIII(Si2O7)29-, and rutile-like layers, (VO2)42.4-. These two layers are interconnected by comer-sharing oxygen atoms between Si2O7 groups and VO6 octahedra in the rutile layers along the c-axis. Distorted octagonal tunnels running along the b-axis are created by the network of polyhedra. The La3+ and Ca2+ ions located in these tunnels are statistically disordered. The magnetic susceptibility of La3.4Ca0.6V5Si4O22 follows a Curie-Weiss behavior with an effective moment indicative of two localized unpaired electrons in the VIII(Si2O7)29- layer. The (VO2)42.4- mtile layer forms an extended V-V bond along the b-axis; however, La3.4Ca0.6V5Si4O22 is an insulator with room-temperature resistivity of the order of 106 Ω cm along the b-axis.

Original languageEnglish (US)
Pages (from-to)5994-5998
Number of pages5
JournalInorganic Chemistry
Volume33
Issue number26
DOIs
StatePublished - Dec 1 1994
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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