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TT: Tiefe Temperaturen

TT 6: Solids At Low Temperature: Amorphous and Tunnel Systems, Glasses, ...

TT 6.9: Vortrag

Montag, 27. März 2006, 12:45–13:00, HSZ 105

Low-temperature investigation of phase transition in SrTiO₃ (001) single-crystal plate — •Alexander A. Levin, Dirk. C. Meyer, and Peter Paufler — Institut für Strukturphysik, TU Dresden

A (001) SrTiO₃ single-crystal plate is investigated in a temperature range 300 K...25 K by means of wide-angle X-ray scattering (WAXS) under vacuum conditions. Depending on the quality of surface preparation, the plates exhibited different structural characteristics and low-temperature phase-transition and domain behaviour.

At the polished surface of the single-crystal plate, in a cooling cycle a cubic (C-phase, space group Pm-3m) - tetragonal (T-phase, space group I4/mcm) phase transformation is recorded at a temperature of approx. 107.5 K close to the known C-T-phase transition temperature of bulk SrTiO₃ (105 K - 108 K). When cooling, the formation of domains of T-phase with different orientation ([110] and [001]) was observed starting from a temperature of 80 K. The volume fraction of the orientation domains mentioned above changed step-wise with decrease of temperature.

The non-polished surface remained in a single-domain state down to a temperature of 25 K. Considerable decrease of the profile parameters of the X-ray reflection of non-distorted cubic phase were recorded below a temperature of about 90 K referred to C-T phase transition. The lowering the temperature of C-T transition can be attributed to non-bulk plate constraint conditions and coexistence of ideal perovskite and distorted regions in the non-polished side of the plate.

This work is supported by DFG, FOR 520.