Dielectric and structural studies of Ba2MTi2Nb3O15 (BMTNO15, M=Bi3+,La3+,Nd3+,Sm3+,Gd3+) tetragonal tungsten bronze-structured ceramics

Abstract

Articles you may be interested inEvolution of structure, dielectric properties, and re-entrant relaxor behavior in Ba5LaxSm1−xTi3Nb7O30 (x = 0.1, 0.25, 0.5) tungsten bronze ceramics

A Crystal-Chemical Framework for Relaxor versus Normal Ferroelectric Behavior in Tetragonal Tungsten Bronzes

“…25,26 19 and Stennett et al 20 and the patterns in Figure 4 are indexed accordingly. The diffraction patterns from Sr based TTBs are similar to those published by Levin et al 19 and Stennett et al 20 ( Figure 5) has a commensurate superstructure consistent with the cell proposed by Labbe et al 27 Figure 15b. 12 The incommensurate superstructure in Pb 1-x Ba x Nb 2 O 6 is reported to exist above T C 12 in a manner similar to that described by Levin and co-workers.…”

“…[12][13][14] Filled TTBs, such as Ba 4 Na 2 Nb 10 O 30 , have also been shown to exhibit ferroelectricity concomitant with an incommensurate superstructure similar to that in unfilled stoichiometries. 13,15,16 In 2003, a family of filled TTB structured ceramics were reported based on Ba 4 RE 2 Ti 4 Nb 6 O 30 (RE = rare earth) [17][18][19][20] which built on earlier work by Ikeda et al 21 Ba 4 Figure 2a,b. 19,20 The incommensurately modulated compositions (RE = La, Bi) are relaxors whereas commensurately modulated ones (RE = Nd, Sm, Gd) are ferroelectric at room temperature and their Curie temperature (T C ) increases with decreasing ionic radius.…”

“…13,15,16 In 2003, a family of filled TTB structured ceramics were reported based on Ba 4 RE 2 Ti 4 Nb 6 O 30 (RE = rare earth) [17][18][19][20] which built on earlier work by Ikeda et al 21 Ba 4 Figure 2a,b. 19,20 The incommensurately modulated compositions (RE = La, Bi) are relaxors whereas commensurately modulated ones (RE = Nd, Sm, Gd) are ferroelectric at room temperature and their Curie temperature (T C ) increases with decreasing ionic radius. 20 Levin and co-workers 19 concluded that relaxor behaviour in this family of TTBs is coupled directly to the incommensurate modulation whereas ferroelectricity is induced by the transition to commensurate octahedral tilting, stable for RE having ionic radii < 1.3 Å.…”

“…19,20 The incommensurately modulated compositions (RE = La, Bi) are relaxors whereas commensurately modulated ones (RE = Nd, Sm, Gd) are ferroelectric at room temperature and their Curie temperature (T C ) increases with decreasing ionic radius. 20 Levin and co-workers 19 concluded that relaxor behaviour in this family of TTBs is coupled directly to the incommensurate modulation whereas ferroelectricity is induced by the transition to commensurate octahedral tilting, stable for RE having ionic radii < 1.3 Å. 19 This model not only explained the coupling of relaxor/ferroelectric behavior to the appearance of incommensurate/commensurate superstructure but also gave a plausible rationale for the increase in T C with decreasing RE ionic radius, i.e.…”

Structural phase transitions in the Ag2Nb4O11–Na2Nb4O11 solid solution

“…Of these, perovskites are by far the most widely studied, due in part to their simple prototype structure, the wide range of compounds that can be formed and their existing markets for applications. Ferroelectricity also exists in other oxide groups, such as tungsten bronzes [1], pyrochlores [2,3] and bismuth-layered structures including Aurivillius phases [4]. These structures are all based on corner-sharing octahedra that are able to undergo distortions that can lead to the development of a switchable polarisation.…”