Stability of the monoclinic phase in the ferroelectric perovskite PbZr1-xTixO3 Noheda, B.; Cox, D.E.; Shirane, G.; Guo, R.; Jones, B.; Cross, L.E. Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. Recent structural studies of ferroelectric PbZr 1Ϫx Ti x O 3 ͑PZT͒ with xϭ0.48, have revealed a monoclinic phase in the vicinity of the morphotropic phase boundary ͑MPB͒, previously regarded as the boundary separating the rhombohedral and tetragonal regions of the PZT phase diagram. In the present paper, the stability region of all three phases has been established from high-resolution synchrotron x-ray powder-diffraction measurements on a series of highly homogeneous samples with 0.42рxр0.52. At 20 K, the monoclinic phase is stable in the range 0.46рxр0.51, and this range narrows as the temperature is increased. A first-order phase transition from tetragonal to rhombohedral symmetry is observed only for xϭ0.45. The MPB, therefore, corresponds not to the tetragonal-rhombohedral phase boundary, but instead to the boundary between the tetragonal and monoclinic phases for 0.46рxр0.51. This result provides important insight into the close relationship between the monoclinic phase and the striking piezoelectric properties of PZT; in particular, investigations of poled samples have shown that the monoclinic distortion is the origin of the unusually high piezoelectric response of PZT.

(1−x) Bi(Mg 1/2 Ti 1/2 ) O 3 –x PbTiO 3 polycrystalline ceramics were investigated for potential as high-temperature piezoelectric materials. A morphotropic phase boundary (MPB) between tetragonal (T) and rhombohedral (R) ferroelectric (FE) phases, which exhibited enhanced piezoelectric activity and a ferroelectric–paraelectric phase transition at 478 °C was observed at x≈0.37. Electron diffraction patterns (x⩽0.37) contained discrete superlattice reflections at 12{hkl} positions arising from antiphase rotations of the O octahedra, consistent with R3c space group symmetry. These reflections were diffuse at the MPB (x=0.38) and absent in the T phase (x=0.5). In the unpoled state, FE R (x=0.35) ceramics revealed a polar microdomain structure whereas the T phase (x=0.5) contained classic {110} twin domain boundaries. However, poled R samples underwent a field-induced transformation to an aligned domain structure with {110} twin boundaries similar to those in the T phase. Correlations are made between structure and properties for these piezoelectric materials.

Single crystals of Ba(ZrxTi1−x)O3 were grown by templated grain growth (TGG). Millimeter size single crystals of Ba(ZrxTi1−x)O3 were produced by heating a BaTiO3 crystal in contact with a sintered polycrystalline matrix of 4.5, 5.0, or 8.5 mol % Zr-doped barium titanate for 30 h at 1350 °C. To facilitate boundary migration, the ceramic compact was made 3 mol % TiO2 excess. The 4.5 and 5.0 mol % Zr-doped crystals were orthorhombic at room temperature, and for a pseudocubic (001) orientation, they showed remanent polarizations of 13 μC/cm2 and a high field d33 of 340–355 pC/N. The 8.5 mol % Zr-doped crystal [again oriented along the pseudocubic (001)] was rhombohedral at room temperature with a remanent polarization of 10 μC/cm2. A k33 value of 0.74 from resonance measurements was observed for the 4.5 mol % Zr-doped crystal.

Conditional averages of turbulent flow quantities can be approximated in terms of unconditional correlation data by means of stochastic estimation. The validity and accuracy of this procedure are investigated by comparing stochastic estimates to conditional averages measured in four turbulent flows: grid turbulence, the axisymmetric shear layer of a round jet, a plane shear layer, and pipe flow. Comparisons are made for quantities that are separated from the conditional data in time or space, and for turbulent pressures, as well as turbulent velocities. In each case, the linear estimate accurately represents large scale structure. Nonlinear quadratic estimation shows little improvement over linear estimation, because the second-order terms are small for probable values of the turbulent fluctuations.

Traditionally, nuclear power plant control rooms have been designed according to a single-sensor single-indicator (SSSI) philosophy. Various researchers have proposed new display design principles, such as the mapping principle, which tries to overcome the limitations associated with the traditional approach by displaying higher-order functional information directly to operators. The mapping principle is exemplified by the Rankine cycle display, which is an overview display for monitoring and diagnosing the state of nuclear power plants. In this paper we present the results of the first formal evaluation of the Rankine display, comparing it with an SSSI display and a variation of the SSSI that also contains a pressure-temperature graph. The performance of undergraduate and graduate students in mechanical and nuclear engineering is compared with that of licensed nuclear power plant operators. Participants in each of these three groups were required to detect and diagnose abnormalities in dynamic scenarios using one of the three display. The results indicate that the nuclear power plant operators outperformed the other two groups and that the Rankine cycle display led to more accurate detection and diagnosis performance than did either of the other two displays. Finally, we discuss some additional issues that must be addressed before one can recommend that the Rankine cycle display be implemented in commercial nuclear power plant control rooms.