Berlin 2005 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 23: Posters Superconductivity, Solids at Low Temperature

TT 23.8: Poster

Montag, 7. März 2005, 14:00–18:00, Poster TU D

Synthesis and Characterization of new Re_xW_1−xO₃ Phases — •Ch. Helbig¹, B. Rohrmoser¹, K. Tröster¹, D. Shorokhov¹, G. Heymann², G. Eickerling¹, R. Herrmann¹, E.-W. Scheidt¹, and W. Scherer¹ — ¹CPM, Universität Augsburg, 86135 Augsburg, Germany — ²Department Chemie, LMU, 81377 München, Germany

In this presentation we outline new synthetic routes to the small class of vacancy perovskites M_1−xM_x′O₃ (M, M′ = transition metal) which allows to control their physical properties by variation of the ratio of the metal cations. Employing highly topotactical Chimie Douce methods [1] or alternatively high pressure/high temperature routes [2] we were able to synthesize mixed WO₃ and ReO₃ phases and characterize them with respect to their crystal chemistry and physical properties. The chosen parent compounds strongly differ in their electronic and structural behavior.The d¹-system ReO₃ has metallic character and cubic symmetry (Pm3m), whereas the d⁰-system WO₃ is an insulator and displays various structural phase transitions between 1170 K and 230 K. However, the structures of all these WO₃ phases can be derived by group-subgroup relationships from the ReO₃ structure [3]. For Re_xW_1−xO₃ (x=0.25) a metal to semiconductor transition was predicted in the literature [2]. In this contribution, however, we provide for the first time a systematic study of the electronic and magnetic properties of mixed WO₃ and ReO₃ phases. [1] See for example: M. Figlarz, Chemica Scripta 28, 3, (1988) [2] A. W. Sleight, J. L. Gillson, Sol. St. Comm. 4, 601, (1966) [3] O. Bock, U. Müller, Z. Anorg. Allg. Chem. 628, 987, (2000)