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DF: Dielektrische Festkörper

DF 7: Phasenüberg
änge und Spektroskopie

DF 7.5: Vortrag

Donnerstag, 11. März 2004, 16:10–16:30, H11

Diffuse phase transition in BaTi_1−xSn_xO₃ — •Volkmar Müller¹, Horst Beige¹, and Hans-Peter Abicht² — ¹FB Physik, Martin-Luther-Universität Halle — ²FB Chemie, Martin-Luther-Universität Halle

We investigated the influence of Sn-substitution on the diffuse phase-transition (DPT) of BaTi_xSn_1−xO₃ (BTS) solid solutions. Thermal expansion, dielectric and electromechanical experiments have been carried out, both for the pure compounds (x=0 and x=1, respectively), and for various BTS compositions with 0.025 ≤ x ≤ 0.2. This composition range covers both the diffuse phase transition state and the ferroelectric relaxor state of BTS. The thermal expansion of BTS is nonlinear, both due to thermally generated impurities and, below the Burns-temperature T_d, due to nanopolar regions in the paraelectric phase. Deviations from the Curie-Weiss law of the permittivity and the non-Debye dispersion due to the precursor polarization in the Burns-phase of BTS are studied. Resonance-like spectra of DC-biased bar-shaped samples provide information about the complex coupling factor and the elastic anomaly accompanying the DPT. Large-field electromechanical and dielectric experiments reveal the decisive role of the Sn-content on the unhysteretic P(E)-dependence in the slim-loop region as well as on the coupling between polarization and electromechanical strain.

This contribution was supported by Deutsche Forschungsgemeinschaft, Schwerpunktprogramm No-dqSubstitutionseffekte in ionischen FestkörpernNo-dq