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Diffuse phase transformations in neodymium-doped $BaTiO_3$ ceramics

Murugaraj, P and Kutty, TRN and Rao, Subba M (1986) Diffuse phase transformations in neodymium-doped $BaTiO_3$ ceramics. In: Journal of Materials Science, 21 (10). pp. 3521-3527.

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Phase transitions in $BaTiO_3$ doped with neodymium have been studied using temperaturecapacitance measurements, differential scanning calorimetry, X-ray powder diffraction and electron paramagnetic resonance spectroscopy. The coexistence of a para-electric cubic phase with the ferroelectric tetragonal and orthorhombic phases is noticed within the temperature range corresponding to the stability region of the latter phases in undoped $BaTiO_3$. The broad maximum in the effective dielectric constant shifts to lower temperature with increase in neodymium content. The heat of transformation measured at the Curie point tends to zero above 3.5 at% Nd and the phase transition gradually approaches the second order. These are characteristics of a diffuse phase transformation. Using the quantitative results from the above studies, a T-x topological diagram is constructed for the $BaTiO_3-xNd$ system where x < 5.5at%. The phase contents vary with processing parameters as well as grain size, and the very existence of more than one phase in a given area of the T-x diagram indicates the metastable thermodynamic equilibrium prevailing in $BaTiO_3$-Nd ceramics. The inhomogeneous distribution of lattice defects may be the major cause for such a behaviour.

Item Type: Journal Article
Publication: Journal of Materials Science
Publisher: Springer Netherlands
Additional Information: Copyright of this article belongs to Springer.
Department/Centre: Division of Chemical Sciences > Materials Research Centre
Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited: 17 Apr 2008
Last Modified: 19 Sep 2010 04:44
URI: http://eprints.iisc.ac.in/id/eprint/13750

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