Phase transitions and electrical characterizations of (K0.5Na0.5)2x(Sr0.6Ba0.4)5-xNb10O30 (KNSBN) ceramics with 'unfilled' and 'filled' tetragonal tungsten-bronze (TTB) crystal structure

Alkali-doped strontium barium niobate (K0.5Na0.5)(2r)(Sr0.6Ba0.4)(5-x)Nb10O30 (KNSBN) ceramics has been prepared by a conventional solid-state reaction method. The alkali-dopant concentration x has been varied from 0.24 to 1.15 so that the crystal structure was transformed from 'unfilled' to 'filled' tetragonal tungsten bronze (TTB) structure. Apart from the change in the structural properties, the effects of the alkali-dopants on the phase transition as well as ferroelectric, piezoelectric and pyroelectric properties have also been investigated. Phase transitions have been studied in the temperature range of -200 degrees C to 350 degrees C. The origins of these phase transitions are discussed. The addition of the alkali-dopants enhances the ferroelectric, piezoelectric and pyroelectric properties of the KNSBN ceramics. Alkali-doping also favors abnormal grain growth and thus results in a porous microstructure, which might contribute to the enhancement of the pyroelectric performance. (C) 2012 Elsevier Ltd. All rights reserved.