Abstract. Relaxors are very interesting materials but most of the time they are restricted to perovskite materials and thus their flexibility is limited. We have previously shown that tetragonal tungsten bronze (TTB) niobate Ba₂PrFeNb₄O₁₅ was a relaxor below 170 K and that Ba₂NdFeNb₄O₁₅ displays a ferroelectric behavior with a T_C = 323 K. On scanning the whole solid solution Ba₂Pr_xNd_1−xFeNb₄O₁₅ (x = 0, 0.2, 0.4, 0.5, 0.6, 0.8 and 1), we demonstrate here a continuous crossover between these end member behaviors with a coexistence of ferroelectricity and relaxor in the intermediate range. This tunability is ascribed to the peculiar structure of the TTB networks which is more open than the classical perovskites. This allows for the coexistence of long range and short range orders and thus opens up the range of relaxor materials.

Print publication: Issue 45 (11 November 2009)
Received 2 July 2009, in final form 27 September 2009
Published 9 October 2009