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Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 59 for “"rhombohedral"”.
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The Structure of Selected Rhombohedral Borides
Made available in DSpace on 2014-12-12T00:32:34Z (GMT). No. of bitstreams: 1 7310015.pdf: 3395933 bytes, checksum: f6c7daf4c5c32eb576a077feb56755d9 (MD5) Previous issue date: 1972
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The Electronic Compressibility of Rhombohedral Graphene Multilayers
… non-trivial. The low-energy bands of rhombohedral graphene multilayers possess both of these ingredients, making this a promising class of materials in which to search for correlated topological electronic ground states. This thesis describes our electronic compressibility measurements …
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Magnetic and electric properties of bismuth ferrite lead titanate ceramics
… are shown to exhibit mixed tetragonal (P4mm) and rhombohedral (R3c) phase perovskite distortions from 0.4 ≤ x < 0.75, where at x ~ 0.75 a morphotropic phase boundary exists and compositions x > 0.75 are entirely rhombohedral. From extensive use of neutron diffraction experiments, the phase …
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New perspectives of pure and lanthanum modified lead zirconate titanate crystalline solutions
… systems (R- and M-type) were found in the rhombohedral phase field of lead zirconate titanate (PZT). A hierarchy of domain structure was observed in the high temperature rhombohedral ferroelectric (FE) state, where local octahedral tilt domains on the scale of $\sim$50 A existed within the …
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The Premartensitic Transitions of Titanium Nickel: Observation of a Charge Density Wave in a Binary Alloy
… At 224 K, the lattice undergoes a sudden rhombohedral distortion which makes the lattice and superstructure commensurate. This transition is coincident with the prominent specific heat and resistivity anomalies. On further cooling, the rhombohedral distortion increases, but the …
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Grain Boundary Structure in Alumina
… show, in addition to basal twins, (SIGMA) = 7 rhombohedral twins and two distinct varieties of 10(')11 twins new to alumina. All these boundaries are analyzed using the CSL/DSCL model and an idealized axial ratio c/a = SQRT.(15/2); 0 lattice methods are employed to estimate the error introduced …
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High-temperature structural properties of the refractory rare-earth tungsten oxides
… temperature transformation was from an fcc to a rhombohedral structure and occurred in the range 1250-1300 C. In the higher temperature transition the rhombohedral phase transformed back into an fcc structure, which was initiated at approximately 1600 $^{\circ}$C. The transformation process in …
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On the spheroidal graphite growth and the austenite solidification in ductile irons
… was developed. Both hexagonal structure and rhombohedral structure were found in the spheroidal graphite particles. Possible crystallographic defects associated with hexagonal-rhombohedral structure transition were discussed. Schematic models for introducing tilt angles to the graphite …
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BaTiO₃ based materials for piezoelectric and electro-optic applications
… in a composition range that stabilizes the rhombohedral phase. These materials were prepared as bulk polycrystals using a standard solid-state reaction technique in order to test the piezoelectric and dielectric properties. Some compositions were then chosen for thin film deposition. The …
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High-pressure states of bismuth
… gaps the electronic energy bands, producing a rhombohedral metal with a tiny overlap of conduction and valence bands. The resulting solitary free electron per 100,000 atoms can travel large distances in high-purity crystals, leading to a host of unusual properties. We show that the rhombohedral …
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Low Temperature Single-Crystal X-ray Diffraction on A(1-x)A'xMnO3 (A=La,Eu and A'=Ba,Sr)
… to magnetic and electronic properties) of rhombohedral La0.815Ba0.185MnO3 and orthorhombic La0.89Sr0.11MnO3 in dependence on temperature, the studies of the monoclinic symmetry of La0.815Ba0.185MnO3 at T=160K and the evidences of the splitting of the A-site in Eu0.60Sr0.40MnO3. We …
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Magmatic processes that generated the rim andesites of Medicine Lake Volcano, N. California
… fugacity recorded in coexisting spinel and rhombohedral oxides varies from NNO (Nickel - Nickel Oxide) to NNO 0.7 log units. Experiments performed at 1 kbar - H20 saturated conditions at the NNO buffer on a primitive andesite reproduce most of the major element compositional variability …
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Electronic Structure of Three Center Two Electron Bonds in Boron Rich Materials: A Study of Molecules, Crystals, and Amorphous Solids using the ab initio Orthogonalized Linear Combination of Atomic Orbitals Method
… been shown that isomers of carborane, α and β rhombohedral boron, α and β tetragonal boron, γ boron, and boron carbide tend to form icosahedral structures. If the icosahedra were formed with pure boron, it has been demonstrated that there is an insufficient number of electrons to populate all …
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Transport Characteristics of Amorphous Semiconductors in the Dilute Carrier Regime: A Variable Range Hopping Treatment
… boron and carbon atoms in an initially pristine rhombohedral arrangement of icosahedra. We find the transport characteristics to be most sensitive to the size of the icosahedral clusters relative to their mean separation, while it is robust with respect to disorder. In particular, the transport …
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Microstructures and oxidation properties in hafnium-tantalum-nitride ceramics
… in the diffusion couples. It was shown that the rhombohedral ζ-Hf_4 N_3 phase, like other M_4 X_3 UHTCs, formed through elemental migration along close-packed planes from FCC structures. Lattice parameter calculations from the high temperature diffusion couple verified homogeneity ranges of …
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Structures and relationships of some Perovskite-type compounds
… parametric relation is derived between w and the rhombohedral cell angle, α, or the corresponding hexagonal axial ratio c/a . A wide range of atomic structures based on a framework of regular or slightly distorted octahedra sharing corners can be derived from this model. A number of compounds of …
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Investigation of the crystal structure, elemental composition and peculiarities of ionic transport in Li+ solid electrolytes /
… The investigated materials belong to rhombohedral, hexagonal, monoclinic and cubic symmetries. A partial substitution of Al3+ by Y3+ in Li1.3AlyYx–yTi1.7(PO4)3 (x = 0.3; y = 0.1, 0.2) causes the increase in the lattice parameters and theoretical density of the compound. The results of …
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Properties and Applications of Amorphous Gallium Arsenide Annealed to a Polycrystalline Form
… that conduction is due to the formation of rhombohedral arsenic forming in between GaAs grains. These arsenic grains form a network around the GaAs grain structure, creating a conduction path through the material. Silicon doping of the amorphous GaAs lowers the amount of arsenic …
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Investigations of the electronic, vibrational and structural properties of single and few-layer graphene
… the spatial distribution of Bernal (ABA) and rhombohedral (ABC) stacking in trilayer and tetralayer graphene. We find that 15% of exfoliated graphene trilayers and tetralayers are comprised of micrometer-sized domains of rhombohedral stacking, rather than of usual Bernal stacking. The accurate …
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Two phase magnetoelectric epitaxial composite thin films
… substrates are tetragonal, orthorhombic, and rhombohedral respectively. The larger constraint stress induces higher piezoelectric constants in tetragonal PFN thin film. Epitaxial thin-layers of Pb(Zr0.52Ti0.48)O3 (or PZT) grown on (001), (110), and (111) SrTiO3 substrates are tetragonal, …
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