bluuebunny/crossref_metadata_2025_split huggingface dataset:
GalnAsSb Materials for Thermophotovoltaics
Authors: Wang C. A. , Turner G. W. , Manfra M. J. , Choi H. K. , Spears D. L. 
Published: April 2011

ABSTRACTGai1−xInxASySb1-y (0.06 < x < 0.18, 0.05 < y < 0.14) epilayers were grown lattice-matched to GaSb substrates by low-pressure organometallic vapor phase epitaxy (OMVPE) using triethylgallium, trimethylindium, tertiarybutylarsine, and trimethylantimony. These epilayers have a mirror-like surface morphology, and exhibit room temperature photoluminescence (PL) with peak emission wavelengths (λP,300K) out to 2.4 μm. 4K PL spectra have a full width at half-maximum of 11 meV or less for λP,4K < 2.1 μm (λP,300K = 2.3 μm). Nominally undoped layers are p-type with typical 300K hole concentration of 9 × 1015 cm−3 and mobility ∼ 450 to 580 cm2/V-s for layers grown at 575°C. Doping studies are reported for the first time for GalnAsSb layers doped n type with diethyltellurium and p type with dimethylzinc. Test diodes of p-GalnAsSb/n-GaSb have an ideality factor that ranges from 1.1 to 1.3. A comparison of electrical, optical, and structural properties of epilayers grown by molecular beam epitaxy indicates OMVPE-grown layers are of comparable quality.
Formation of Double-Channel Mesa Structure for GaSb-BASED MID-Infrared Laser
Authors: Piotrowska Anna , Guziewicz Marek , Kamińska Ieliana , Papis Ewa 
Published: April 2011

ABSTRACTSemiconducting antimonide compounds have received increasing attention as the alternative materials for mid-infrared photonic devices, with a variety of applications such as remote sensing, pollution monitoring, and molecular spectroscopy. For many, if not all these devices it is necessary to pattern antimonide films into mesa or line structures. While plasma etching techniques have played an increasing role in producing such features, little was reported until now on dry etching of GaSb- and AlSb-containing alloys. In this paper we present the results of our recent work towards the development of the technology for GaSb-based ridge wave-guide laser emitting at 2–2.3 μm at RT. Specifically, we discuss the fabrication of double-channel mesa structure in AlxGai1−xAsySb1−y/GaSb (x=0.2–0.5) heterostructure materials by RIE technique. The effects of gas and material composition, rf power, pressure and temperature on etching characteristics were studied with special attention paid to surface quality, etching rate and etching profile, which are crucial for obtaining a single mode waveguide. CCI2F2/H2 and CCI4/H2 process chemistries were investigated which shows the latter to provide vertical sidewalls and residue free etch surfaces at controllable etch rates.
MBE Growth and Characterization of InSb/AlxIn1−xSb Strained Layer Structures
Authors: Goldammer K. J. , Liu W. K. , Ma W. , Santos M. B. , Hauenstein R. J. , O'steen M. L. 
Published: April 2011

ABSTRACTThree types of structures were fabricated using molecular beam epitaxy. High-resolution x-ray diffraction measurements demonstrated the high structural quality of InSb/AlxIn1−xSb superlattices grown on InSb and GaAs substrates. Hall effect data revealed the effect of substrate temperature on autocompensation in InSb δ-doped with Si. Two-dimensional electron systems with a high mobility were realized in InSb quantum wells with AlxIn1−xSb barriers δ-doped with Si.
High Pressure Synthesis of Solid State Materials
Authors: Mcmillan Paul F. 
Published: April 2011

AbstractWithin the ASU MRSEC, we are using a combination of high pressure synthesis techniques (multi-anvil, piston cylinder), combined with in situ studies in diamond anvil cells, and ab initio calculations, to prepare a range of new materials at high pressure, and to study their physical properties under extreme conditions of pressure and temperature. Work in progress includes experiments on nitrides, particularly glasses and crystalline materials based in the P3N5-HPN2-PON system, silicate and germanate perovskites and related vanadates and niobates, and high hardness materials in the B-C-N-0 system. Some of our recent results are presented.
New One-Dimensional Commensurate and Incommensurate Structural Forms of Sr-Co Oxide
Authors: Christoffersen R. , Jacobson A. J. , Hegwood S. L. , Liu L. 
Published: April 2011

AbstractNew forms of Sr-Co oxide with one-dimensional structures related to mixed-layer hexagonal perovskites have been synthesized and characterized by TEM. Crystals of Sr5Co2O12 grown from molten KOH flux and oxidized under slow cooling have structures based on a 3/2 ratio of mixed [Sr3CoO6] and [Sr3O9] layers. This is the first known structure with layers of this type stacked in a non-integer ratio, yielding chains of face-sharing octahedral and trigonal prismatic Co-sites with a 3 + 1 sequence along the c-axis. In oxygen-deficient Sr5Co2O12−x, the {110} structural modulation of the stoichiometric 5:4 phase becomes rotated to an irrational orientation, possibly in association with vacancy ordering, forming an incommensurate superstructure. For the compound Sr6Co5O15, previously known to have a 1/1 ratio of [Sr3CoO6] and [Sr3O9] layers with a 4 + 1 octahedral/trigonal prismatic site sequence, introduction of excess oxygen atoms leads to formation of a commensurate rhombohedral superlattice in which c is doubled relative to the stoichiometric 6:5 phase.
Synthesis of GaSr2Can−1CunO2n+3(n = 2 − 5) Prepared by Solid-State Reaction Method
Authors: Chavira E. , Aguila E. , Baños L. , Navarro O. 
Published: April 2011

AbstractWe present some experimental results of the family of compounds with a general formula GaSr2Can−1CunO2n+3(n = 2,3, 4, 5). This system has been synthesized using the solid-state reaction method at ambient pressure. We have found that the reaction temperature for these compounds is 930±3°C; the samples melt just above this temperature. The powder diffraction data were analyzed assuming a single-phase and the obtained structure is different to the one prepared at high pressure [1,2]. However, comparing the powder patterns we found that the compounds are isostructural to the Al — Sr — Ca — Cu — O system prepared at high pressure [3]. For n = 2,3,4 and 5 a shift of the (105) peak has been observed, which is due to the increases in the number of Ca and Cu — O2 planes in the crystalline structure. Notice that to obtain a single-phase for the above compounds, high pressure is not necessary.
Stability of Ionic Tin(II) in a Chloride Fluoride Matrix: the Unexpected Ba1−xSrxCl1+yF1−y Solid Solution Crystallizing in the Bacif Structure
Authors: Denes Georges , Bratigny Julie , Le Roux David , Muntasar Abdualhafeed 
Published: April 2011

AbstractWe have prepared a wide Ba1−xSrxCl1+yF1−y solid solution (0<x<0.25, −0.20<y<0.20) that has the BaClF structure without any sign of lattice distortion or ordering of the cations or of the anions other than that already present in BaClF. Furthermore, 119Sn Mossbauer spectroscopy shows that tin(ll) is present in this material in the form of Sn2+ ions instead of being covalently bonded Sn(ll) with a stereoactive lone pair of electrons, which is nearly always the case when the anions are small and strongly electronegative, like for F and Cl. The tin situation is similar to that observed in SnCl2.
Synthesis and Structure of Novel Ternary Manganese Tellurides: MMnTe2 (M = Li, Na), Na3Mn4Te6, and Na3Mn4.7Te6
Authors: Wang Chwanchin , Kim Joonyeong , Hughbanks Timothy 
Published: April 2011

AbstractThe synthesis and structure of four ternary manganese tellurides are reported. All the title compounds form layered structures wherein MnTe4 tetrahedra are the fundamental building blocks. In two compounds MMnTe2 (M = Li, Na), MnTe4 tetrahedra share three corners in the formation of [MnTe3/3Te]1− layers, the fourth Te is bound to only one Mn and formally bears a negative charge. MnTe4 tetrahedra share both corners and edges in the formation of [Mn4Te6]3− and [Mn4.7Te6]3− layers in Na3Mn4Te6 and Na3Mn4.7Te6, respectively. Structural relationships between these ternary tellurides and oxides will be discussed.
Ln3Cu4P4O2: a New Lanthanide Transition Metal Pnictide Oxide Structure Type
Authors: Cava R. J. , Zandbergen H. W. , Krajewski J. J. , Siegrist T. , Hwang H. Y. , Ramirez A. P. , Batlogg B. 
Published: April 2011

AbstractA new type of lanthanide transition metal pnictide-oxide, Ln3Cu4P4O2 (for Ln = La, Ce, and Nd), is reported. The crystal structure is made from Ln2O2 layers of the Pb2O2 type stacked with layers of Cu2P2 tetrahedra. The existence of a homologous series of compounds with similar chemistry connecting the BiCuOSe and ThCr2Si2 structure types is indicated. The resistivity of La3Cu4P4O2 is metallic, with no superconductivity observed above 2K. The Ce and Nd compounds have magnetic susceptibilities characteristic of the trivalent Lanthanides. The Ce compound orders magnetically at approximately 0.8 K.
Critical Transport and Magnetization of La0.67Ca0.3MnO3
Authors: Jeffrey Snyder G. , Hiskes R. , DiCarolis S. , Beasley M. R. , Geballe T. H. 
Published: April 2011

AbstractThe critical magnetic properties of bulk La0.67Ca0.3MnO3 and magnetoresistance of a thin film with the same Tc were measured and critical exponents determined. The magnetization data can be scaled with β = 0.3 and γ = 0.9, except above Tc which appears to be affected by a region where X3 (M = XH + X3H3) is positive. An M2 dependence of the magnetoconducitvity is observed above Tc. Below Tc, however, such a correspondence between the critical magnetic and transport behavior is not found.
The Ir3Ge7 (D8f) Structure: an Electron Phase Related to γ-Brass
Authors: Swenson D. 
Published: April 2011

AbstractThe crystallographic similarity between the Ir3Ge7 (D8f) and γ-brass (Cu5Zn8, D82) structures is discussed. By considering all phases known to possess the Ir3Ge7 structure, it is shown that phases of this structure type obey essentially the same electron concentration rules as does γ-brass, possessing on average 22 atoms/formula unit. Based on crystal-chemical considerations, it is further suggested that the Ir3Ge7 structure may be considered to be a structural derivative of γ-brass, in which 12 atoms have dropped out of the γ-brass lattice and the remaining atoms have undergone a certain amount of rearrangement in order to accommodate such a large concentration of vacancies. Finally, as further support of this idea, the phase NiGa4 is presented as an example of another γ-brass derived structure which contains crystallographic features of both γ-brass and the Ir3Ge7 structure.
On the Brass- and Silver-Colored Forms of PtGa2
Authors: Morosin B. , Swenson D. 
Published: April 2011

AbstractPtGa2has previously been reported to exist as both a brass-colored, fluorite-structured phase and as a silver-colored alloy of unknown crystal structure. The crystal structure of the silver-colored form is reported here, along with a discussion of the stoichiometric factors responsible for the polymorphy of this phase. The silver-colored form belongs to the space group141/acd, with the lattice parametersa= 8.5544(4) andc= 21.574(17) Å, andZ= 32. The structure consists of layers of Pt and Ga stacked along the c axis, in which two crystallographically different Pt and Ga atoms have similar environments involving eight and nine nearest neighbors, respectively. This structural arrangement may be the prototype for a family of ternary platinum metal-Group B-based phases. The present investigation also necessitates changes in the currently accepted Ga-Pt phase diagram. Stoichiometric PtGa2undergoes a structural transformation upon cooling from a brass-colored fluorite structure to this silver-colored, tetragonal structure. However, the transformation is inhibited if the composition of the fluorite-structured phase is Ga-poor.
Modeling Phase Stability in a(B1/3B'2/3)O3 Perovskites
Authors: McCormack R. , Burton Benjamin P. 
Published: April 2011

AbstractOrder-disorder phenomena on the simple-cubic B-site sublattice in A(B1/3B'2/3)O3 perovskites is examined. A simple cubic groundstate analysis in the cube approximation reveals that this approximation is inadequate for A(B1/3B'2/3)O3 perovskites, because it cannot predict a common experimentally-observed [111] superstructure. A partial vertex enumeration technique is used to demonstrate that a 12 interaction subset of the cube + linear triplet approximation is sufficient. First-principles calculations were performed for Ba(Zn1/3Ta2/3)O3 (BZT) and Pb(Mg1/3Nb2/3)O3 (PMN), two technologically interesting materials, in an effort to construct generalized Ising model Hamiltonians to enable simulations of these materials. Both ionic model (SSCAD) and pseudopotential (PP) calculations were done, enumerating the relative energies of a series of B-site superstructures. Structural hierarchies are reasonble and predict the [111] groundstate for both BZT and PMN, despite the fact that it is not observed in the latter. The pseudopotential results also indicate the possibility of metal-insulator transitions in BZT as a function of B-site configuration.
Structural Modeling Based on the Oxygen Sublattice Features in the Perovskite Family
Authors: Depero L. E. , Sangaletti L. , Parmigiani F. , Giulotto E. , Rollandi L. 
Published: April 2011

AbstractA new approach based on the study of distortion in the AO3 layer of ABO3 perovskites is proposed with the aim to discuss their ferroelectric properties. Rhombohedral distortions exist for either A-O average distances shorter than 2.7 A (space group Nr.161) or A-O distances larger than 3 Å (space group Nr.160). In the case of small distortions tetragonal or orthorhombic symmetries are preferred. Moreover, a relationship between the dimension of the B cation and the distortion in this type of structure has been established. Preliminary results show interesting correlations between distortions in the AO3 plane and the critical temperature of ferroelectric materials.
Influence of Li Addition on the Sintering and Dielectric Properties of PNN-PMW-PT Relaxor Ferroelectrics
Authors: Natarajan Raghu , Dougherty Joseph P. 
Published: April 2011

AbstractCompositions in the PNN-PMW-PT system can be tailored to give high dielectric constant for MLC applications. Low temperature firing of MLC is always advantageous in using the less expensive electrode systems. Controlled addition of LiNO3 reduces the sintering temperature, increases the fired density and influences the microstructure of the ceramics. It also raises the peak dielectric constant and shifts the Curie temperature. The possible role of Li+ in modifying the characteristics of the ceramics is discussed.
Characterization of Cation-Ordering Induced Structures in Ba(Mg1/3Nb2/3)O3-BazrO3 Microwave Ceramics.
Authors: Akbas M. A. , Davies P. K. 
Published: April 2011

AbstractCompositions in the Ba(Mg1/3Nb2/3)O3-BazrO3 (BMN-BZ) pseudo-binary system were prepared to evaluate the effect of BaZrO3 on the B-site cation ordering. While pure BMN adopts a 1:2 ordered structure, space group , 5 to 15 mole% additions of BZ stabilize a cubic 1:1 ordered phase with a doubled perovskite repeat. At higher levels of substitution (>25 mole% BZ), the B-site cations are disordered. Analytical TEM studies revealed that the 1:1 ordering is limited to nanometer-sized domains and the microstructure was found to strongly depend on the thermal history of the ceramics. For example, a cooling rate of 300°C/hr from a sintering temperature of 1640°C produced a partially ordered microstructure comprised of 4–5nm 1:1 domains dispersed in a disordered matrix. A completely ordered structure with 30–40 nm domains could be achieved when the cooling rate was reduced to 10°C/hr. The structure of the ordered 1:1 phases is interpreted using a “random layer” model in which one site is occupied exclusively by Nb, and the second contains a random distribution of all the remaining cations. Similar thermal annealing experiments were also conducted in an attempt to grow the 1:1 ordered domains in PMN-type (PbMg1/3Nb2/303) relaxor ferroelectric ceramics. Through experiments on PbZr03 (PZ)-doped PMT (PbMg1/3Ta2/3O3), the first observation of thermally induced domain growth in this class of relaxor ceramics are presented. These results cannot be explained by the widely accepted “space charge” model for relaxor ferroelectrics, but instead favor a charge-balanced random layer model for the 1:1 cation order.
Effect of Defects on Dielectric Properties in KTiOPO4, KTiOAsO4, RbTiOAsO4 and CsTiOAsO4 Single Crystals
Authors: Guo A. R. , Cheng Z. -Y. , Katiyar R. S. , Guo Ruyan , Bhalla A. S. 
Published: April 2011

AbstractDielectric measurements were carried out in single crystals of KTiOPO4, KTiOAsO4, RbTiOAsO4 and CsTiOAsO4. All of the materials exhibit a clear dielectric relaxation process in the low temperature range and a conductance mechanism in the high temperature range. The dielectric relaxation process can be well described by the Debye dielectric model with an activation energies of 0.8 eV, 0.5 eV and 0.4 eV respectively. The relaxation process is associated with the deviation of the alkali ions from its ideal lattice positions. The high temperature conductance is associated with the motion of the alkali ions from one lattice site to another. Therefore, both the low temperature relaxation process and the high temperature conductance originate from different features of defect behavior of alkali ions in the cage structure of these materials.
Electrical Conductivity and Structure of Nanocrystalline CeO2 Thin Films
Authors: Kosacki Igor , Anderson Harlan U. 
Published: April 2011

AbstractThe results of structural and electrical measurements of nanocrystalline CeO2 thin films are presented. A correlation between the electrical conductivity and microstructure has been observed and discussed. The electrical properties of nanocrystalline CeO2 thin films are attributed to a dominant role of grain boundary phase.
Rietveld X-ray Powder Profile Analysis and Electrical Conductivity of Fastion Conducting Gd2(Til-ySny)2O7 Solid Solutions
Authors: Eberman Kevin , Önnerud Per , Yu Tae-Hwan , Tuller Harry L. , Wuensch Bernhardt J. 
Published: April 2011

AbstractThe A3+2B4+2O7 pyrochlores have fast-ion conduction properties that make them attractive candidates for applications in fuel cells. Rietveld powder-profile analysis of x-ray diffraction data has been used to determine structural parameters for Gd2(Ti1-ySny)2O7 solid solutions (y = 0.20, 0.40, 0.60, and 0.80) for correlation with composition-dependence of the specimens' electrical conductivity. In accord with Vegard's law, the lattice constants increase linearly with y as the larger Sn ion replaces Ti4+. The structures in the system remain remarkably ordered in view of the fact that it had been suggested that increasing the average radius of the ions that occupy the B4+ site relative to A3+ drives the system toward a disordered defect-fluorite state. A small but significant increase in mixing of the occupancy of the cation sites was found with increasing y to a maximum of [GdB] = 0.05. We could detect no significant disorder in the anion array. The activation energy and pre-exponential term for oxygen ion conduction were found to increase linearly and exponentially with y, respectively, such that at a given temperature, the ionic conductivity changes by less than an order of magnitude across the system. The behavior is in marked contrast to other systems where the substitution of a larger cation in the B site increases conductivity by up to three orders of magnitude as a consequence of substantial disorder that is introduced in both the cation and anion arrays.
Phase Stability and Properties of Superionic PbSnF4 as a Function of the Method of Preparation
Authors: Calandrino Raimondo , Collin Anthony , Denes Georges , Cecilia Madamba M. , Parris Juanita M. 
Published: April 2011

AbstractSuperionic PbSnF4 can be prepared using a variety of different methods. It crystallizes in various different unit-cells. All structures are closely related to that of the fluorite type structure, with various degrees of order/disorder and different types of superstructures. Reaction of lead(ll) nitrate and stannous fluoride in water gives highly stressed and highly oriented tetragonal α-PbSnF4, however, in HF/H2O, it gives orthorhombic O-PbSnF4, which is also stressed but less. Reactions of solid α-PbF2 with an aqueous solution of SnF2, in excess SnF2, also gives stressed α-PbSnF4. Solid state reactions of SnF2 and PbF2 give unstressed and much less oriented α-PbSnF4 at 250°C, whereas tetragonal β-PbSnF4 is obtained above 270°C and is quenchable to ambient temperature. At 390°C, cubicy-PbSnF4 is obtained, however, this is not quenchable. Ball milling of o-PbSnF4 gives stressed α-PbSnF4, and ball milling of a- and β-PbSnF4 gives microcrystalline γ-PbSnF4. Annealing the latter gives unstressed and non oriented α-PbSnF4. Stirring a slurry of microcrystalline γ-PbSnF4 in water gives α-PbSnF4 except the one originating from o-PbSnF4, which gives back o-PbSnF4. The texture of these phases, and therefore the macroscopic properties related to it, can be drastically modified by modifying the method of preparation.
Sol-Gel Synthesis of the Strontium-Copper Oxycarbonate Superconductor Sr2CuO2(CO3)1−x(BO3)x
Authors: Babcock Audrey J. , Pico Alexander R. , Page Catherine J. 
Published: April 2011

AbstractWe have developed an ambient-pressure sol-gel synthetic route to superconducting borate-doped Sr2CuO2(CO3) using polyether alkoxide precursors. In our sol-gel preparation, the starting solutions contain strontium and copper alkoxide complexes in 2-(2-methoxy-ethoxy)ethanol. Boron is incorporated into the solution by using an aqueous boric acid solution for hydrolysis. Dried gels were examined by x-ray diffraction and thermal gravimetric analysis. By experimenting with various firing sequences and atmospheres we have established a successful route for reproducibly preparing relatively pure Sr2CuO2CO3 and boron-doped phases. Final products were characterized by x-ray diffraction, elemental analysis and magnetic susceptibility. Samples of nominal composition Sr2CuO2(CO3)0.85(BO2)0.15 are superconducting with a Tc(onset) of ∼25K. Subsequent treatment at 1100°C and 3 GPa for one hour increased Tc(onset) to ∼35K.
A Quantitative Tunneling/Desorption Model for the Exchange Current at the Porous Electrode/Beta"- Alumina/Alkali Metal Gas Three Phase Zone at 700–1300K
Authors: Williams R. M. , Ryan M. A. , Saipetch C. , LeDuc H. G. 
Published: April 2011

AbstractThe exchange current observed at porous metal electrodes on sodium or potassium beta"-alumina solid electrolytes in alkali metal vapor is quantitatively modeled with a multi-step process with good agreement with experimental results. No empirically adjusted parameters were used, although some physical parameters have poor precision. Steps include: (1) diffusion of Na+ ions to the reaction site; (2) stretching of the Na+ ionic bond with the β3"-alumina surface to reach a configuration suitable for accepting an electron to form a surface bound Na0 atom; (3) electron tunneling from the Mo electrode to the ions; and (4) desorption of Na0 atoms weakly bound at the reaction site on the β"-alumina surface; (5) electron tunneling between Na0 or Na+ on the defect block and (6) Na0 and/or Na+ mobility on the spinel block surface may extend the reaction area substantially.The rate is increasingly dominated by the region close to the three-phase boundary as temperature increases and the rate near the three-phase boundary increases fastest, because desorption has a higher energy than reorganization. At high temperatures, surface diffusion of Na+ ions from the defect block edges to the spinel block edges is responsible for an increase in the total effective reaction zone area near the three-phase boundary.