High-Pressure Synthesis, Crystal Structure, and Semimetallic Properties of HgPbO.

The crystal structure of HgPbO was studied using single-crystal X-ray diffraction and powder synchrotron X-ray diffraction. The structure was well characterized as a centrosymmetric model with a space group of R-3 m [hexagonal setting: a = 5.74413(6) Å and c = 7.

Studies of the antiferrodistortive transition in EuTiO3.

Structural studies of EuTiO3, conducted using synchrotron x-ray powder diffraction, reveal the sensitivity of this material to defects. The presence of a single tetragonal-cubic (I4/mcm-Pm-3m) transition is confirmed. Neutron diffraction measurements show EuTiO3 to have a G-type antiferromagnetic arrangement.

Neutron powder diffraction study of the magnetic structure of EuZrO₃.

Neutron powder diffraction experiments on the orthorhombic perovskite EuZrO₃ show it to have an antiferromagnetic G-type magnetic structure with the magnetic moments aligned parallel to the a-axis. The orthorhombic crystal structure is a consequence of cooperative rotations of the corner-sharing ZrO₆ octahedra. The crystal structure does not change significantly below the Néel temperature, ∼4.

Synthesis, crystal structure, and electronic properties of the tetragonal (RE(I)RE(II))3SbO3 phases (RE(I) = La, Ce; RE(II) = Dy, Ho).

In our efforts to tune the charge transport properties of the recently discovered RE(3)SbO(3) phases (RE is a rare earth), we have prepared mixed (RE(I)RE(II))(3)SbO(3) phases (RE(I) = La, Ce; RE(II) = Dy, Ho) via high-temperature reactions at 1550 °C or greater. In contrast to monoclinic RE(3)SbO(3), the new phases adopt the P4(2)/mnm symmetry but have a structural framework similar to that of RE(3)SbO(3). The formation of the tetragonal (RE(I)RE(II))(3)SbO(3) phases is driven by the ordering of the large and small RE atoms on different atomic sites.

Decoupling the electrical conductivity and Seebeck coefficient in the RE2SbO2 compounds through local structural perturbations.

Compromise between the electrical conductivity and Seebeck coefficient limits the efficiency of chemical doping in the thermoelectric research. An alternative strategy, involving the control of a local crystal structure, is demonstrated to improve the thermoelectric performance in the RE(2)SbO(2) system. The RE(2)SbO(2) phases, adopting a disordered anti-ThCr(2)Si(2)-type structure (I4/mmm), were prepared for RE = La, Nd, Sm, Gd, Ho, and Er.

Structural evolution and properties of solid solutions of hexagonal InMnO3 and InGaO3.

Solid solutions InMn(1-x)Ga(x)O(3) (0 ≤ x ≤ 1) have been investigated using magnetic, dielectric, specific heat, differential scanning calorimetry (DSC), and high-temperature powder synchrotron X-ray diffraction (HT-SXRD) measurements. It was found that samples with 0.5 ≤ x ≤ 1 crystallize in space group P6(3)/mmc with a ~ 3.

Synthesis, crystal and electronic structures of new narrow-band-gap semiconducting antimonide oxides RE(3)SbO(3) and RE(8)Sb(3-delta)O(8), with RE = La, Sm, Gd, and Ho.

In the search for high-temperature thermoelectric materials, two families of novel, narrow-band-gap semiconducting antimonide oxides with the compositions RE(3)SbO(3) and RE(8)Sb(3-delta)O(8) (RE = La, Sm, Gd, Ho) have been discovered. Their synthesis was motivated by attempts to open a band gap in the semimetallic RESb binaries through a chemical fusion of RESb and corresponding insulating RE(2)O(3). Temperatures of 1350 degrees C or higher are required to obtain these phases.

Composition, structure, bonding and thermoelectric properties of "CuT2P3" and "CuT4P3", members of the T(1-x)(CuP3)x series with T being Si and Ge.

Through electron microprobe analysis, X-ray and neutron diffraction, it has been established that "CuT(2)P(3)" and "CuT(4)P(3)" (T = Si, Ge) adopt the cubic or tetragonally distorted zinc blende structures in which two element mixtures are present on both atomic sites. One site contains the Cu/T mixture while the other site is occupied by T and P. The structure of "CuT(2)P(3)" and "CuT(4)P(3)" can be derived from that of silicon or germanium, in which the single Si or Ge site is broken into two independent sites by the preferential Cu and P substitution.

Local structural origins of the distinct electronic properties of Nb-substituted SrTiO3 and BaTiO3.

The perovskite SrTiO3 becomes metallic with 0.03% to 0.1% Nb substitution on the Ti site, while BaTiO3 remains insulating above 10% Nb substitution.

Towards an ultrasensitive method for the determination of metal impurities in carbon nanotubes.

Residual catalyst metal nanoparticles remain one of the major obstructions in the utilization of carbon nanotubes (CNTs) in many areas owing to their ability to participate in redox chemistry of biomarkers. Presented here is a comparative study of several techniques for quality control of carbon nanotubes in terms of metallic impurities, namely magnetic susceptibility, electron paramagnetic resonance, energy-dispersive X-ray spectrometry, X-ray photoelectron spectroscopy, and thermogravimetric analysis. It is found that the dc magnetic susceptibility is the most sensitive method such that the difference between two CNT samples that underwent slightly different treatments can be detected, whereas the two samples are indistinguishable by other techniques.