Observation of short-lived local polar states induced by applied tip biases in BaTiO3-based relaxor ferroelectric ceramics

Using piezoresponse force microscopy imaging and spectroscopy methods, surface polar states induced by applied tip biases in the ergodic/paraelectric phase of a BaTiO3-based relaxor ferroelectric ceramic have been observed. The induced polar state appears to be short-lived (typical lifetime only a few seconds) and dependent on the voltages applied and their duration. The observed piezoresponse hysteresis and relaxation behavior is primarily interpreted with respect to the picture of the polar nano-region dynamics, as proposed for lead-based relaxors. Spatially resolved piezoresponse relaxation mapping reveals the presence of sub-micron correlated features, presumably due to A-site chemical inhomogeneity as supported by site-correlated elemental mapping microanalysis.Q.L., Y.L., and R.L.W., acknowledge the support of the Australian Research Council (ARC) in the form of ARC Discovery Grants. Y.L. also acknowledges support from the ARC Future Fellowships Program

Structural Stability and Microwave Dielectric Properties of (1-\u3cem\u3ex\u3c/em\u3e)Ba(Mg\u3csub\u3e1/2\u3c/sub\u3eW\u3csub\u3e1/2\u3c/sub\u3e)O\u3csub\u3e3−\u3cem\u3ex\u3c/em\u3e\u3c/sub\u3eBa(RE\u3csub\u3e2/3\u3c/sub\u3eW\u3csub\u3e1/3\u3c/sub\u3e)O\u3csub\u3e3\u3c/sub\u3e (RE = Sm, Dy, Y, Yb) Solid Solutions

The structural stability and microstructure of (1−x)Ba(Mg1/2W1/2)O3−xBa(RE2/3W1/3)O3 (RE = Sm, Dy, Y, Yb) ceramics have been investigated by X-ray diffraction (XRD), Raman spectrometry, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) in this work. Microwave dielectric properties were studied in the frequency range 7–13 GHz. Phase-pure solid solutions formed in space group Fm-3m within the compositional range of x = 0.01–0.05. The local ordering of the two cations (RE3+ and W6+ or Mg2+) produced an internal lattice-induced strain and charge-imbalance clusters which greatly affected the structural stability and Q × f value

Order–disorder transition in the (1−x)Li 2_{2} TiO 3_{3} –xMgO system (0 ≤ x ≤ 0.5)

The order–disorder phase transition of magnesium lithium titanate solid–solution (1−x)Li2TiO3–xMgO (0 ≤ x ≤ 0.5) ceramics prepared by conventional solid-state processing has been examined. The phase and structural analysis was carried out using electron diffraction, neutron diffraction and high-resolution transmission electron microscopy. Both electron and neutron diffraction results revealed the onset of an order-to-disorder transition at 0.3 < x < 0.4. Superlattice reflections found in certain regions of x = 0.2 samples and most areas of x = 0.3 samples were caused by a twin structure stabilized by Mg incorporation. Rietveld refinements of neutron diffraction data suggested a random distribution of Mg on the Li 4e sites and equal distribution of Mg on the two Ti 4e sites for x ≤ 0.3. As the Mg content continues to increase, the crystal symmetry transforms from monoclinic to cubic rocksalt. Consequently, the cation ordering on the 8f and 4d sites of the C2/c structure became corrupted and turned into short-range ordering on the 4a sites of a cubic structure with Image ID:c1ra00677k-t1.gif symmetry, resulting in diffuse scattering in electron diffraction patterns