Ferroelectric domains in PZT ceramics at the morphotropic phase boundary. Can the splitting of reflections in SAED patterns be used for the distinction of different pseudo-cubic phases?

Tetragonal, rhombohedral and monoclinic ferroelectric domains can all occur in morphotropic PbZr1-xTixO3 (PZT) ceramics. In this article, the influence of these domains on the splitting of reflections in selected area electron diffraction (SAED) patterns along the main pseudo-cubic zone axes is reported. The orientation of the domain wall in a transmission electron microscopy image with respect to the splitting of reflections in the diffraction pattern has to be considered for the interpretation. The distinction of tetragonal and rhombohedral splitting is achieved for a pronounced splitting except for with the domain wall edge on. As the monoclinic structure contains tetragonal as well as rhombohedral distortions, the distinction of monoclinic symmetry from tetragonal and rhombohedral based only on the splitting of reflections is not possible. Conceivable models of configurations of monoclinic subdomains inside the existing tetragonal or rhombohedral microdomains are derived from group-subgroup relations. Some experimental observations are given, which can only be explained by these models

Symmetry of domains in morphotropic PbZr_{1−x}Ti_{x}O_{3} ceramics

PbZr1−xTixO3 (PZT) ceramic samples with compositions over the morphotropic phase boundary (MPB) ranging from 45/55 to 60/40 [(1−x)/x] are studied by transmission electron microscopy combined with convergent-beam electron diffraction (CBED). All point-group symmetries debated for morphotropic PZT, 4mm, m, and 3m, are identified. Up to PZT 54/46 the symmetry is mainly tetragonal within lamellar domain configurations. From PZT 52/48 to PZT 54/46 nanodomains evolve within the tetragonal microdomains and monoclinic symmetry is identified within the same domain configurations, together with tetragonal symmetry for PZT 54/46. For PZT 55/45 up to PZT 60/40 rhombohedral symmetry is observed. Rhombohedral domains, as identified by CBED, are characterized by their width, curved domain walls, and grainy inner contrast. This contrast, together with anisotropic first-order Laue-zone intensities, implies that local deviations from 3m symmetry may exist within rhombohedral domains. Between PZT 54/46 and PZT 55/45 the morphology of the microdomains changes abruptly. For PZT 54.5/45.5 both types of domain configurations coexist within the same grain. For PZT 56/44 a tetragonal inclusion within a rhombohedral matrix is identified by CBED. On the other side of the MPB, domains with a rhombohedral appearance are found in PZT 53.5/46.5. These observation were less frequent but show that coexistence is present in ceramic samples around the MPB

A Bayesian pricing model for CAT bonds

This paper examines the impact of the 2005 hurricane season, particularly Hurricane Katrina, on the pricing of CAT bonds. We examine whether highly rated CAT bonds demonstrate a different relationship than subinvestment bonds between objective risk measures and the spread. The theoretical framework for this relationship is based on the Lance Financial (LFC) model, introduced by Lane (Rationale and results with the LFC cat bond pricing model, Discussion paper, Lane Financial LLC, Wilmette, 2003). The empirical results of treed Bayesian estimation confirm that the severity component of the spread has an increased impact, indicating a shift in investor perception during the pricing process. The impact of the conditional expected loss also significantly increases, but it contributes through its interaction with the attachment probability rather than through its variance. Finally, we show that the influence of conditional expected loss is also increased by investment-grade ratings, because investors who demand highly rated bonds may be more concerned about possible losses than junk bond investors

Crystal symmetry in single domains of PbZr0.54Ti0.46O3

This work focuses on the crystal symmetry of morphotropic PbZrxTi1−xO3 (PZT). The crystal symmetry is investigated within single domains of ≈30–100 nm width by convergent beam electron diffraction (CBED). The composition PbZr0.54Ti0.46O3 was chosen for experiments at room temperature and ≈300 °C. The observed zone axis symmetry at room temperature was a (1̅ 10) mirror in some domains whereas symmetry was broken in neighboring domains. Therefore the highest crystal symmetry that can be attributed with certainty to the probed volume is monoclinic. The local symmetry of single cells might be lower due to disordered displacements of the cations. At ≈300 °C the zone axis symmetry had changed to a (100)pc mirror that only occurs in the tetragonal phase of PZT

Depotmanagement - standardisierte Vermoegensverwaltung fuer den Privatkunden: eine analytische und empirische Studie zu aktuellen Konzepten deutscher Banken

Available from Bibliothek des Instituts fuer Weltwirtschaft, ZBW, D-21400 Kiel W 965 (15) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

The quasi-binary phase diagram BaF2-BaBr2 and its relation to the x-ray storage phosphor BaFBr : Eu2+

In order to understand the formation and stoichiometry of the x-ray storage phosphor BaFBr: Eu2+, the phase diagram of the quasi-binary BaF2-BaBr2 system has been investigated. The phase diagram was obtained by means of differential thermal analysis and temperature controlled x-ray diffraction experiments. The resulting phase diagram indicates that BaFBr forms a compound with no detectable solid solubility for neither BaF2 nor BaBr2. Experiments to obtain non-stoichiometric BaFBr via the synthesis route using BaF2 and NH4Br as proposed in the literature could not be verified. It will be shown that the type of colour centre created during x-ray irradiation is related to the non-stoichiometry of the starting compositions before sintering. A surplus of either barium fluoride or barium bromide during sintering allows the controlled formation of F(Br-)- and F(F-)-centres, respectively