Manipulation of polar order in the “empty” tetragonal tungsten bronzes: Ba4-xSrxDy0.671.33Nb10O30, x = 0, 0.25, 0.5, 1, 2, 3
Date
15/08/2016Metadata
Show full item recordAbstract
A series of “empty” tetragonal tungsten bronze (TTB) ferroelectrics, Ba4-xSrxDy0.67□1.33 Nb 10O30 (x = 0, 0.25, 0.5, 1, 2, 3; □ = vacancy), is reported. With increasing x the unit cell contracts in both the ab plane and c-axis; x ≤ 1 compounds are normal ferroelectrics (FE) with decreasing TC as x increases, while x ≥ 2 are relaxor ferroelectrics (RFE) with associated frequency dependent permittivity peaks and with similar Tm and Tf (Vogel-Fulcher freezing temperatures) values. This observation is rationalised by differing cation occupancies: for x ≤ 1, Sr2+ principally occupies the A2-site (co-occupied by Ba2+ with the A1-site occupied by Dy3+ and vacancies); for x ≥ 2 significant Sr A1-site occupation leads to the observed RFE characteristics. This FE to RFE crossover is consistent with a previously proposed TTB crystal chemical framework where both a decrease in average A-site size and concurrent increase in A1-site tolerance factor (tA1) favour destabilization of long range polar order and relaxor behaviour. The effect of increasing tA1 as a result of Sr occupancy at the A1 site is dominant in the compounds reported here.
Citation
Gardner , J & Morrison , F D 2016 , ' Manipulation of polar order in the “empty” tetragonal tungsten bronzes: Ba 4-x Sr x Dy 0.67 1.33 Nb 10 O 30 , x = 0, 0.25, 0.5, 1, 2, 3 ' , Applied Physics Letters , vol. 109 , no. 7 , 072901 . https://doi.org/10.1063/1.4960712
Publication
Applied Physics Letters
Status
Peer reviewed
ISSN
0003-6951Type
Journal item
Description
JG would like to thank the EPSRC for provision of a studentship via the doctoral training grant (EP/K503162/1).Collections
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