Fast ion conductor

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Fast ion conductors, also known as solid electrolytes, are solid state electrical conductors which conduct due to the movement of ions through voids in their crystal lattice. One component of the structure, cationic or anionic, is essentially free to move throughout the structure, acting as charge carrier.

Fast ion conductors are intermediate in nature between crystalline solids (see crystal) which possess a regular structure with immobile ions, and liquid electrolytes which have no regular structure and entirely mobile ions.

Solid electrolytes find use in batteries and fuel cells, and in various kinds of chemical sensors.

Examples of fast ion conductors include sodium chloride, beta-alumina solid electrolyte, zirconium dioxide and silver iodide.

Some examples include:

• Inorganic materials:
  • Sodium chloride
  • Zirconium dioxide doped with calcium oxide and yttrium oxide, which is conductive for O^2- ions and is used in oxygen sensors
  • Beta-alumina solid electrolyte used as a membrane in several types of molten salt electrochemical cells
  • Lanthanum(III) fluoride, conductive for F^- ions, used in some ion selective electrodes
  • Silver sulfide, conductive for Ag⁺ ions, used in some ion selective electrodes
  • Silver iodide, conductive at higher temperatures
  • Lead(II) chloride, conductive at higher temperatures
  • Some perovskite ceramics - strontium titanate, strontium stannate - conductive for O^2- ions
  • Zr(HPO₄)₂.nH₂O - conductive for H⁺ ions
  • UO₂HPO₄.4H₂O - conductive for H⁺ ions
  • Conductive ceramics - eg. NASICON (Na₃Zr₂Si₂PO₁₂), a sodium super-ionic conductor

• Organic materials:
  • Gels - polyacrylamides, agar - polymer holds a solution of ion electrolyte
  • A salt dissolved in a polymer - eg. lithium perchlorate in polyethylene oxide
  • Polyelectrolytes
  • Ionomers - eg. Nafion, a H⁺ conductor