New Gadolinium Based Ferroelectric Phases Derived from the Tetragonal Tungsten Bronze (TTB).

Substitution of Pb with Gd in the Pb 2 KNb 5 O 15 phases leads to a new composition of solid solution with chemical composition Pb 2(1 - x ) Gd x K 1 + x Nb 5 O 15 (0 ≤ x ≤ 1) which crystallizes with TTB type structure. Powders are pressed and heated into ceramics and their compaction is about 90%. Thermal evolution of the real part of the dielectric permittivity presents different behavior according to the composition. The dielectric permittivity of compounds with Gd composition above x = 0.30 shows two anomalies. The first one appears at T C and is associated to the ferroelectric-paraelectric phase transition. The origin of the last one at which occurs at T 1 is up to now unknown. Domain structure should exhibit strong changes both with temperature and composition. [ABSTRACT FROM AUTHOR]