Growth and Characterization of Some New Superionic Phosphates

  • K. Byrappa


The search for new sodium superionic conductors is becoming very popular with the development of NASICON whose ionic conductivity is equivalent to that of Na β — alumina. NASICON poses a challenge to Materials Scientists in understanding its structure and conduction mechanism due to the lack of single crystals, non-stoichiometry in the composition, zirconium deficiency, etc. It is a solid solution between NaZr2P3O12– Na4Zr2Si3O12. Then came several new triorthophosphates, which became popular as NASICON analogues with their simple structures and stoichiometric composition. However, all the compounds whether NASICON or NASICON analogues always had only the triorthophosphate end members and their structures were directly related to Na3Sc2P3O12. Here, the author reports the ionic conductivity in condensed phosphates, particularly pyrophosphates, for the first time, showing high ionic conductivity. These pyrophosphates have been grown by hydrothermal method. The author has reported some of these pyrophosphates in brief as the perspective superionics very recently. These condensed phosphates are much easier to obtain in the form of single crystals with stoichiometric composition. The structures vary from the regular NASICON type. Although, cations form the usual octahedra, Na+ atoms lying in the cavities, but the framework linking differs. The conductivity is attributed to the diffusion of Na+ through a network of tunnels in a rigid structure made up of pyrophosphate anions sharing corners with ZrO6/MO6 octahedra. This has opened a new chapter in the search for new Na+ superionic conductors even among the condensed phosphates and silicates. The pyrophosphates considered here have a wide range of cationic groups. The author has discussed in the present work, the growth, structure and impedence spectroscopy of these new pyrophosphate superioncs.


Solid State Ionic High Ionic Conductivity Superionic Conductor Trivalent Metal Hydrothermal Growth 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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© Elsevier Science Publishers Ltd. 1990

Authors and Affiliations

  • K. Byrappa
    • 1
  1. 1.The Mineralogical InstituteUniversity of MysoreManasagangotri MysoreIndia

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