Fig. 1: Basic material properties.
From: Structural origins of dielectric anomalies in the filled tetragonal tungsten bronze Sr2NaNb5O15
a A [001] projection of the aristotype TTB structure with tetragonal P4/mbm symmetry. The unit cell of the tetragonal aristotype is outlined in black; magenta boxes emphasise the mirror planes present in the aristotype to outline enantiomorphic structural units. b [100]supercell and (c) [001]supercell projections of the \({\Gamma }_{3}^{-}\) and \({\Gamma }_{5}^{-}\) distortions, respectively, as found in the supercell, showing the distortions as greyed overlays on the undistorted structure which is coloured according to (a). Note the concerted shift parallel to cs of all oxygen sites relative to the metal centres in (b), and parallel to as in (c) with significant additional distortion of the A2 sites for which the long axis aligns parallel to as. d Plot of the dielectric response in SNN, replotted with permission (© 2021 Elsevier) from ref. 3.
