INVESTIGATION OF THE FERROELECTRIC PHASE

WITH THE TETRAGONAL TUNGSTEN BRONZE STRUCTURAL TYPE IN THE TERNARY SYSTEM PbNb2O6 - NaNb03 - LaFeO3

 

M. Bouziane1*, A. Benabad1, J.-C. Niepce2, B. Elouadi3

1 Laboratoire de Chimie du Solide Appliquée, Laboratoire Associé Francophone N°501,

Faculté des Sciences, Avenue Ibn Batouta, BP 1014, Rabat - Maroc.

2 Laboratoire de Recherches sur la Réactivité des Solides, UMR 5613 CNRS/Université de Bourgogne,

BP 47870, 21078 Dijon Cedex, France

3 Laboratoire d’Elaboration Analyse Chimique et Ingénierie des Matériaux, Université de la Rochelle,

avenue Michel Crépeau, 17042 La Rochelle Cedex 01, France

*Corresponding author. Email: bouzianemeryem@yahoo.fr

Received: 26 June 2008; revised version accepted: 19 August 2008

 

Abstract

     A crystal chemical study of the ternary system PbNb2O6 – NaNbO3 – LaFeO3, has allowed to delimit a wide homogeneous region within the triangle PbNb2O6 – Pb2NaNb5O15 – Pb1.875La1.25Nb3.75Fe1.25O15 crystallising with the tetragonal tungsten bronze structural type. The compositional dependence of TC and the lattice parameters for the analysed solids solutions has evidenced. For example, two main variations could be pointed out versus composition: i) a diminution of the orthorhombic distortion                             d = [(b-a)/(b+a)], with a and b representing regular lattice parameters; ii) the ferroelectric relaxor behaviour enhanced as the lattice contains more different ions, in agreement with the expected correlative cationic disorder.

 

Keywords: Tetragonal tungsten bronze; Ternary system; Dielectric relaxor; Disorder.

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