New Li + ferroelectric conductors with tetragonal tungsten bronze structure

• Published in: Solid state ionics Vol. 127; no. 3; pp. 231 - 240
• Main Authors: Hornebecq, V., Réau, J.M., Ravez, J.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 02.01.2000; Elsevier Science
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Dielectric, piezoelectric, ferroelectric and antiferroelectric materials; Dielectrics, piezoelectrics, and ferroelectrics and their properties; Diffusion in solids; Exact sciences and technology; Ferroelectric conductors; Ferroelectricity and antiferroelectricity; Physics; Self-diffusion and ionic conduction in nonmetals; Tetragonal tungsten bronze oxides; Transport properties of condensed matter (nonelectronic); Tetragonal tungsten bronze oxides; Ferroelectric conductors; Lithium oxides; Inorganic compounds; Property composition relationship; Transition element compounds; Ionic conductivity; Tantalum oxides; Lead oxides; Experimental study; Ferroelectricity; Ferroelectric materials; Tungsten bronze; Impedance; Quaternary compounds
• ISSN: 0167-2738; 1872-7689
• DOI: 10.1016/S0167-2738(99)00301-X

The evolution of conductivity in tetragonal tungsten bronze (TTB) oxides belonging to the Pb 5(1− x) Li 10 x Ta 10O 30 solid solution was studied using two techniques: a.c. complex impedance spectroscopy and the four-probe method. The results obtained from both techniques allowed the correlation of the evolution of conductivity with composition. Indeed, the conductivity mainly appears to be governed by the total number of Li + ions in the structure. Furthermore, it seems that when the number of Li + ions in the structure is small, two separated regions appear: • a low temperature region (LT), characterized by activation energy Δ E LT, a very small number of mobile ions and a low value of the prefactor σ 0; • a high temperature region (HT), characterized by activation energy Δ E HT (Δ E HT>Δ E LT), a larger number of charge carriers and a higher value of the prefactor σ 0. The existence of these two regions is explained in terms of extrinsic–intrinsic behavior. Dielectric measurements were also performed, with the substitution 2Li +–Pb 2+ leading to a decrease of the Curie temperature which is explained in terms of chemical bonding and antagonist effects.