Phase transitions in fluoride KFe 2 F 6 with tetragonal tungsten bronze structure

Горев, М. В.; Flerov, I. N.; Tressaud, A.; Мolokeev, Maxim S.; Карташев, А. В.; Pogorel’tsev, E. I.; Bayukov, O. A.

doi:10.1016/j.jfluchem.2014.09.031

Cited by 2 publications

(1 citation statement)

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“…The high temperature, frequency independent peak in the dielectric data corresponds with this loss of superstructure indicating a transition from the low temperature Bbm2 superstructure to a simpler high temperature orthorhombic structure with comparable metrics to the aristotype cell (i.e., no superstructure is detectable using PND). Refinements using the simple orthorhombic Pbam structure, previously reported for Pb 4.5 Ca 0.5 Ta 10 O 30 and KFe 2 F 6 , result in good agreement between calculated and observed patterns (Figure S3); however, further study of the structure with, e.g., high temperature SAED, etc., would be required to conclusively assign this space group. It should be noted that on the basis of P – E data (discussed later) the material is not polar above 480 K; this is consistent with the assignment of Pbam symmetry.…”

Section: Resultssupporting

confidence: 65%

Relaxor-to-Ferroelectric Crossover and Disruption of Polar Order in “Empty” Tetragonal Tungsten Bronzes

Gardner

Tang

et al. 2016

Chem. Mater.

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Combined temperature-dependent structural and electrical characterization of a series of "empty" ferroelectric tetragonal tungsten bronzes (TTBs) of composition Ba 4 (La 1-x Nd x ) 0.67 ! 1.33 Nb 10 O 30 are reported. The La-material exhibits a temperature dependent crossover from relaxor-ferroelectric to polar (but non-ferroelectric) to linear dielectric behavior. The loss of ferroelectric switching in the polar, non-ferroelectric phase is accompanied by disorder associated with structural relaxation due the significant vacancy concentration at the A1-perovskite-like site. In this disordered regime, large polarization can be re-established with application of sufficient electric field, however relaxation back into the disordered phase occurs on removal of the field as indicated by the loss of remenant polarization. The field against which "backswitching" (depolarization) occurs increases with temperature indicating increasing stability of the disordered regime. The disordered phase can be de-stabilized by substituting Nd for La at the A1-site and which reintroduces "normal" ferroelectric behavior. IntroductionThe field of polar dielectrics (piezo-, pyro-and ferro-electrics) is dominated by oxides with the perovskite structure.1, 2 The role of compositional tuning of perovskites and structural

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Section: Resultssupporting

confidence: 65%