• O G Palanna

      Articles written in Bulletin of Materials Science

    • Phase transition in copper(II) pyrovanadate

      N Suresh Rao O G Palanna

      More Details Abstract Fulltext PDF

      A new phase Cu2V2O7 synthesized, exhibits phase transitions between 475°C and 500°C. These phase transitions are reversible with ease in contrast toαβ phase transition at 712°C of Cu2V2O7 phase reported earlier. These phase transitions are identified by DTA technique and characterized by detailed XRD investigations at different temperatures. The crystal structures of these Cu2V2O7 phases are related to either thortveitite (Sc2Si2O7) type or a modification of it.

    • Phase transitions in copper(II) orthovanadate

      N Suresh Rao O G Palanna

      More Details Abstract Fulltext PDF

      Data on the polymorphs of copper(II) orthovanadate are reported. The Cu3V2O8 phase synthesized in this laboratory exhibits phase transitions between 460° and 560°C. These phase transitions are identified through detailed DTA and high temperature XRD techniques; it is observed that these structural transitions are rapid and reversible. The crystal structure of Cu3V2O8 is similar to that of Mg3V2O8, Zn3V2O8, Co3V2O8 and Ni3V2O8.

    • Electrical and magnetic studies of iron (III) vanadate

      N Suresh Rao O G Palanna

      More Details Abstract Fulltext PDF

      Iron(III) vanadate (FeVO4) is an n-type semiconductor between 300 and 800 K. Electrical conduction in this phase occurs due to small deviation from oxygen stoichiometric composition. The mechanism of electrical transport is of a thermally activated hopping of charge carriers (electrons) on equivalent iron lattice sites. The FeVO4 obeys Curie-Weiss law between 80 and 300 K. The measured magnetic moment (μeff) of Fe3+ ion in FeVO4 is 5·270 BM at 298 K, which is lower than theμspin only value. The predominant exchange interactions are the weak 90° M-O-M superexchange and M-O-O-M super-super-exchange. The negative Weiss constantϑ=− 30 K of the phase indicated the possibility of an antiferromagnetic ordering of the iron(III) vanadate lattice. The IR absorption spectrum of FeVO4 gave bands at 990, 900, 825 and 725 cm−1 due to the presence of distorted VO4 polyhedra of the lattice.

    • Electrical, thermal and infrared studies of cerium(III) orthovanadate

      N Suresh Rao O G Palanna

      More Details Abstract Fulltext PDF

      Cerium(III) orthovanadate with a small deviation from stoichiometric composition is ap-type semiconductor between 30 and 800°C. The electrical conduction in cerium(III) orthovanadate is due to thermally activated hopping of holes on equivalent Ce3+-Ce4+ lattice sites. The DTA result of CeVO4 indicated a possible phase transition at about 70°C. The IR spectrum of the sample showed bands at 865 and 810 cm−1, typical of VO4 group of orthovanadates.

    • Electrical, thermal and infrared studies of cadmium metavanadate

      N Suresh Rao O G Palanna

      More Details Abstract Fulltext PDF

      Cadmium(II) metavanadate has crystal structure related to brannerite (ThTi2O6) structure. The high temperatureβ-CdV2O6 phase isn-type semiconductor between 185 and 750°C. The electrical conduction in theβ-CdV2O6 occurs due to deviation from oxygen stoichiometric composition of the lattice. The seebeck coefficient (α) of the sample is negative and constant in the entire range of investigation. The mechanism of transport in cadmium metavanadate lattice is via thermally activated hopping of localized electrons on vanadium (V5+) sites of the lattice. The DTA result indicated that CdV2O6 undergoes phase transition at 185°C and not at 670°C as reported earlier. There is no DTA evidence to show the possibility ofβα phase reverse transition. The XRD powder patterns of the two modifications are nearly similar indicating brannerite related structures. The infrared absorption band of vanadium-oxygen stretching vibration modes of distorted VO6 octahedra ofβ-CdV2O6 is exhibited at 855 cm−1.

  • Bulletin of Materials Science | News

    • Editorial Note on Continuous Article Publication

      Posted on July 25, 2019

      Click here for Editorial Note on CAP Mode

© 2017-2019 Indian Academy of Sciences, Bengaluru.