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    • Keywords

       

      Dielectrics; ceramics; phase transitions; niobate-titanate systems

    • Abstract

       

      Ferroelectric ceramics of the general formulax (Li1/2 La1/2 TiO3) (1−x) (LiNbO3) have been found to have tungsten bronze (TTB) and ilmenite type structure in the ranges 0·8≤x≤1·0 and 0≤x≤0·2 respectively. The system is biphasic in the other ranges. All single phase materials exhibit dielectric anomalies in the temperature range 300–600 K. The high dielectric constant of the TTB phase is explained as due to the existence of localised rotational excitons arising from a large number of defect structural units and their coupling with one of the low frequency lattice modes. Information about the lattice modes to which the rotational excitons are coupled has been obtained from Raman spectra.

    • Author Affiliations

       

      A M Varaprasad1 2 A L Shashi Mohan1 3 D K Chakrabarty1 A B Biswas1

      1. Solid State Laboratory, Chemistry Department, Indian Institute of Technology, Bombay - 400 076, India
      2. Hindustan Lever Research Centre, Bombay - 400 093, India
      3. Grindwell-Norton Ltd., Bangalore - 560 049, India
    • Dates

       
  • Bulletin of Materials Science | News

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