Premium
Influence of Cobalt Ion Doping on Tetragonal–Orthorhombic Polymorphic Transformation and Dielectric Behavior of Barium Titanate Nanoparticles
Author(s) -
Barik Puspendu,
Jana Atanu,
Kundu Tapas Kumar
Publication year - 2011
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2010.04366.x
Subject(s) - orthorhombic crystal system , materials science , tetragonal crystal system , barium titanate , dielectric , analytical chemistry (journal) , curie temperature , dopant , doping , crystal structure , ferroelectricity , crystallography , mineralogy , chemistry , condensed matter physics , chromatography , physics , optoelectronics , ferromagnetism
Cobalt (Co) ion‐doped barium titanate (BaTiO 3 , BT) nanoparticles were synthesized through the sol–gel route using polyvinyl alcohol. The concentration of Co 2+ varies from 0 to 1.6 mol% in the specimens. Grain size ( D ) ranges from 21 to 29 nm. There exist a new phase of Pnma orthorhombic crystal structure ( o ‐BT‐II) with lattice parameters a =0.6393 nm, b =0.5268 nm, and c =0.8824 nm in addition to P 4 mm tetragonal phase in the specimens. The lattice volume V =0.2971 nm 3 of o ‐BT‐II with z =4 formula units, yields a density ρ=5.214 g/cm 3 . This is a new polymorph in comparison to well‐known P 4 mm tetragonal ( t ) structure, V =0.0644 nm 3 or ρ=6.016 g/cm 3 ( z =1). In 0.6 mol% Co 2+ ‐doped specimen o ‐BT‐II phase exists with maximum volume fraction of 64. Measurement of dielectric properties showed that the room temperature ɛ r value increases with doping. Curie transition temperature T C decreases from 128°C to a minimum value of 43°C in the specimens doped with 0.6 mol% dopant. The presence of space charge polarization in system is clear from dielectric‐frequency dispersion study. The coexistence of tetragonal and orthorhombic ( o ‐BT‐II) phase results an unusual T C shift and diffuse nature of the dielectric behavior.