Structural phase stability, electronic structure, optical properties, and high-pressure behavior of polytypes of In 2 O 3 in three space group symmetry I2 1 3, Ia3 and R3 are studied by first-principles density functional calculations. From structural optimization studies lattice and positional parameters have been calculated, which are found to be in good agreement with the corresponding experimental data. In 2 O 3 of space group symmetry I2 1 3 and Ia3 are shown to undergo a pressureinduced phase transition to IO3 at pressures around 3.83 GPa. From analysis of band structure it is found that In 2 O 3 of space group symmetry I2 1 3 is indirect band gap semiconductors, while the other phase of space group Ia3 is direct band gap. The calculated carrier effective masses for all these three phases are compared with available experimental and theoretical values. From chargedensity and electron localization function analysis it is found that these phases have dominant ionic bonding. The magnitude of the absorption and reflection coefficients of In 2 O 3 with space group Ia3 and R3 are small in the energy range 0-5 eV, so that these materials can re regarded and classified as transparent.

Even though the ZnSb compound has been known for decades and used in the earliest thermoelectric devices, the potential of the material as a modern thermoelectric may be underestimated. We synthesized p‐type doped samples using ball‐milling and hot‐pressing and measured their thermoelectric properties including mobility and carrier concentration. Establishing a single parabolic band (SPB) model using these measurements on the Cu, Sn, and self‐doped samples allows for predictions on the optimum thermoelectric efficiency. It is projected to reach zT = 0.75 at 700 K. Deviations from the SPB model at low carrier concentrations are discussed and impurity band conduction is brought in as a possible explanation.

We prepared ZnSb containing Zn3P2 particles of size ranging from a few tens to several hundred nanometers by melting powders of Zn, Sb, and P. Materials with Zn3P2 content up to 3.75% were made and subsequently ball-milled and hot pressed. A reduction in the thermal conductivity of 15% was achieved. By adding 0.2% Cu the carrier concentration increased an order of magnitude, to 2.0 × 1019 cm−3, while the mobility remained unaffected. The resulting increase in electrical conductivity together with the reduced thermal conductivity, led to a significant increase in the dimensionless figure of merit, in excess of 0.9 around 550 K.

Crystalline and amorphous nanoparticles of silicon in thin silica layers were examined by transmission electron microscopy, electron energy loss spectroscopy, and x-ray photoelectron spectroscopy ͑XPS͒. We used XPS data in the form of the Auger parameter to separate initial and final state contributions to the Si 2p energy shift. The electrostatic charging and electron screening issues as well as initial state effects were also addressed. We show that the chemical shift in the nanocrystals is determined by initial state rather than final state effects, and that the electron screening of silicon core holes in nanocrystals dispersed in SiO 2 is inferior to that in pure bulk Si.

No abstract