Electric field mediated switching of mechanical properties of strontium titanate at room temperature
ABSTRACT In situ application of an electric field to a SrTiO3 single crystal plate during nanoindentation led to a reversible change of the mechanical properties at room temperature. When a field of 8 kV/cm was applied, Meyer hardness and Young's modulus decreased by 0.6 GPa and 11 GPa, respectively. An explanation for this behaviour is given by the diffusion of oxygen vacancies resulting in a distortion of the perovskite-type of structure in the near-surface layer tested by nanoindentation. Simulations using density functional theory support the dependence of elasticity on the presence of vacancies. Thus, we can show the remarkable influence of electric fields on oxide materials which should be considered and used in designing future applications. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
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ABSTRACT: This paper is focused on the mechanical behaviour of single and multilayered ceramic systems on ceramic substrate. The ferro-electric ceramic PLT (Pb 0.9 La 0.1 TiO 3) was deposited using magnetron sputtering on (001) STO (SrTiO 3) and on a YBCO (YBa 2-Cu 3 O 7), as a 200 nm interlayer on STO. DRX and SEM observations were carried out to determine the microstructure of the various films, and TEM cross sections were realised to control the film thickness and grain epitaxial relationships. AFM was used as a roughness controller before and after deposition. Mechanical properties of the films and substrate were determined using micro and nanoindentation tests. Young's modulus and hardness of each system (STO, PLT/STO, YBCO/STO, PLT/YBCO/STO) were calculated and a peculiar phenomenon, associated to the YBCO interlayer addition, was observed. This work shows that YBCO improve mechanical properties of multilayered ceramics.Journal of The European Ceramic Society - J EUR CERAM SOC. 01/2004; 24(5).
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ABSTRACT: Murnaghan's theory of finite strain is developed for a medium of cubic symmetry subjected to finite hydrostatic compression, plus an arbitrary homogeneous infinitesimal strain. The free energy is developed for cubic symmetry to include terms of the third order in the strain components. The effect of pressure upon the second-order elastic constants is found and compared with experiment, with particular reference to the compressibility; the pressure-volume relation in several approximations is compared with the measurements to 100,000 kg/cm2. The simplest approximation is shown to give a satisfactory account of most of the experimental data. The results are also compared with some of the calculations based on Born's lattice theory.Physical Review - PHYS REV X. 01/1947; 71(11):809-824.
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ABSTRACT: The great variability in the electrical properties of multinary oxide materials, ranging from insulating, through semiconducting to metallic behaviour, has given rise to the idea of modulating the electronic properties on a nanometre scale for high-density electronic memory devices. A particularly promising aspect seems to be the ability of perovskites to provide bistable switching of the conductance between non-metallic and metallic behaviour by the application of an appropriate electric field. Here we demonstrate that the switching behaviour is an intrinsic feature of naturally occurring dislocations in single crystals of a prototypical ternary oxide, SrTiO(3). The phenomenon is shown to originate from local modulations of the oxygen content and to be related to the self-doping capability of the early transition metal oxides. Our results show that extended defects, such as dislocations, can act as bistable nanowires and hold technological promise for terabit memory devices.Nature Material 05/2006; 5(4):312-20. · 35.75 Impact Factor