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A simple, near-ambient pressure solid-state method was developed to nominally synthesize BiFe0.5Cr0.5O3. The procedure allowed the gram-scale production of multiferroic samples with appreciable purity and large amounts of Cr incorporation that were suitable for systematic structural investigation by neutron, X-ray, and electron diffraction in tandem with physical characterization of magnetic and ferroelectric properties. The rhombohedrally distorted perovskite phase was assigned to the space group R3c by way of X-ray and neutron powder diffraction analysis. Through a combination of magnetometry and muon spin relaxation, it is evident that there is magnetic ordering in the BFCO phase consistent with G-type antiferromagnetism and a TN ~ 400 K. There is no clear evidence for chemical ordering of Fe and Cr in the B-site of the perovskite structure and this result is rationalized by density functional theory and bond valence simulations that show a lowered energy associated with a B-site disordered structure. We believe that our contribution of a new, low-complexity method for the synthesis of BFO type samples, and dialogue about realising certain types of ordering in oxide perovskite systems, will assist in the further development of multiferroics for next-generation devices. [ABSTRACT FROM AUTHOR]

Iron substitution into sphalerite, ZnS, has been studied systematically by infrared spectroscopy. A range of natural and synthetic compositions, ([Zn.sub.1-x][Fe.sub.x])S, 0 [less than or equal to] x [less than or equal to] 0.24, were examined. The IR spectrum of pure ZnS contains a single strong absorption band at 320 [cm.sup.-1]. With addition of FeS, the spectra become broader and shoulders appear. For compositions [less than or equal to] 9 tool% FeS, a splitting of the main peak occurs, and the spectra show two absorption maxima at approximately 300 and 315 [cm.sup.-1], respectively. The observation of such extra features does not correspond to the usual behavior observed in other ternary mixed crystals, where either one-, two-, or mixed-mode behavior is observed. The spectra can be deconvoluted into up to three peaks, main Peaks A and B at around 300 and 315 [cm.sup.-1], respectively, and a shoulder at around 330 [cm.sup.-1] (Peak C). The positions and area of the peaks do not change significantly with increasing Fe content. The peak at 315 [cm.sup.-1] is the main absorption peak of the host ZnS structure, and the peak at 300 [cm.sup.-1] is an impurity induced mode. An effective linewidth parameter [[DELTA].sub.corr] was determined by autocorrelation analysis for each spectrum, but there are no obvious trends in the values of [[DELTA].sub.corr] that can be interpreted in terms of an inhomogeneous distribution of Fe within the sphalerite structure. Keywords: Fe-bearing sphalerites, infrared spectroscopy, autocorrelation analysis, solid solution

Real part of complex relative dielectric value is relatively decreased as large as ∼5 % from 50 K to 200 K in CaCu3Ti4O12, by applying a 6-T static magnetic field. CaCu3Ti4O12 is thus implied primarily by the negative magnetodielectric effect, as a unified dielectric system in which 1-D finite dipole chains of B-site titanium ions, coexist with a collective of polaron-like 3d-electrons of A-site copper ions: the dipole chains are thermally activated for lattice ionic polarization above 50 K, and suppressed by the short-range hop of these quasi-particles, while their long-range movement are for bulk electronic polarization above 151 K. [ABSTRACT FROM AUTHOR]

We report changes in the metric symmetry of unpoled and electrically poled single crystals of 0.26Pb(In1/2Nb1/2)O3-0.46Pb(Mg1/3Nb2/3)O3-0.28PbTiO3, as revealed by neutron diffraction in conjunction with electrical measurements. The unpoled crystals show relaxor characteristics and an average rhombohedral symmetry that persists from ambient temperature up to the Curie temperature of ∼165 °C. Poling along a [111] direction enhances the rhombohedral distortion away from cubic metric symmetry but appears not to induce any monoclinic phases. By contrast, the poled [001]-oriented crystal has orthorhombic (or monoclinic MC) metric symmetry at 25 °C. An intermediate transition to a metrically tetragonal phase around 120 °C is confirmed for both poled crystals. [ABSTRACT FROM AUTHOR]

Elastic and anelastic properties of poled and depoled single crystals of Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 with compositions close to the morphotropic boundary have been investigated over the temperature range 5-700 K by resonant ultrasound spectroscopy (RUS) at frequencies of 0.1-1.2 MHz. Steep elastic softening occurs in a temperature interval of at least 250 K as the Vogel-Fulcher freezing interval and cubic → tetragonal transition point, Tc, are approached from above. This is understood in terms of coupling between acoustic modes and central peak mode(s) associated with dynamic polar nano regions (PNR's) below the Burns temperature. Acoustic losses occur in a temperature interval of ∼50 K above Tc, associated with slowing down of the PNR dynamics. The cubic ↔ tetragonal and tetragonal ↔ rhombohedral transitions are accompanied by steep minima in elastic properties, closely analogous to the pattern of softening and stiffening observed in sequences of improper ferroelastic transitions in other perovskites. Variations in the magnitudes of acoustic losses at T < Tc correlate with the density of ferroelastic twin walls, from lowest for [001]c-poled and [111]c-poled crystals in the stability fields of the tetragonal and rhombohedral phases, respectively, to highest for unpoled crystals. A simple model of Debye-like peaks in acoustic loss near 100 K has yielded activation energies and attempt frequencies in the same range as those observed from dielectric data in the Vogel-Fulcher freezing interval. These highlight the fact that, in addition to conventional ferroelectric/ferroelastic twin walls, relaxor ferroelectrics contain local structural heterogeneities coupled to strain, which are probably related to the presence of static PNR's preserved even in poled crystals. RUS also provides a convenient and effective means of determining the mechanical quality factor of relaxor ferroelectrics, as functions of both poling history and temperature. [ABSTRACT FROM AUTHOR]