Plasma Electrolytic Modification of Zirconium and Its Alloys: Brief Review.

The review focuses on the surface modification of Zr and its alloys, which is necessary to expand the applications of these kinds of materials. Data on the properties of pure zirconium and its alloys are presented. Since surface engineering and the operation of the above materials are in most cases associated with the formation of oxide coatings, information on the characteristics of ZrO is given.

Electronic properties of single-crystalline FeO.

We synthesized single and polycrystals of iron oxide with an unconventional FeO stoichiometry under high-pressure high-temperature (HP-HT) conditions. The crystals of FeO had a CaFeO-type structure composed of linear chains of iron with octahedral and trigonal-prismatic oxygen coordinations. We investigated the electronic properties of this mixed-valence oxide using several experimental techniques, including measurements of electrical resistivity, the Hall effect, magnetoresistance, and thermoelectric power (Seebeck coefficient), X-ray absorption near edge spectroscopy (XANES), reflectance and absorption spectroscopy, and single-crystal X-ray diffraction.

Giant Room-Temperature Power Factor in p-Type Thermoelectric SnSe under High Pressure.

Materials that can efficiently convert heat into electricity are widely utilized in energy conversion technologies. The existing thermoelectrics demonstrate rather limited performance characteristics at room temperature, and hence, alternative materials and approaches are very much in demand. Here, it is experimentally shown that manipulating an applied stress can greatly improve a thermoelectric power factor of layered p-type SnSe single crystals up to ≈180 µW K cm at room temperature.

Structural Stability and Properties of Marokite-Type γ-MnO.

We synthesized single crystals of marokite (CaMnO)-type orthorhombic manganese (II,III) oxide, γ-MnO, in a multianvil apparatus at pressures of 10-24 GPa. The magnetic, electronic, and optical properties of the crystals were investigated at ambient pressure. It was found that γ-MnO is a semiconductor with an indirect band gap of 0.

Synthesis of Ilmenite-type ε-MnO and Its Properties.

In contrast to the corundum-type AX structure, which has only one crystallographic site available for trivalent cations (e.g., in hematite), the closely related ABX ilmenite-type structure comprises two different octahedrally coordinated positions that are usually filled with differently charged ions (e.

Structural and Magnetic Transitions in CaCoVO Perovskite at Extreme Conditions.

We investigated the structural, vibrational, magnetic, and electronic properties of the recently synthesized CaCoVO double perovskite with the high-spin (HS) Co ions in a square-planar oxygen coordination at extreme conditions of high pressures and low temperatures. The single-crystal X-ray diffraction and Raman spectroscopy studies up to 60 GPa showed a conservation of its cubic crystal structure but indicated a crossover near 30 GPa. Above 30 GPa, we observed both an abnormally high "compressibility" of the Co-O bonds in the square-planar oxygen coordination and a huge anisotropic displacement of HS-Co ions in the direction perpendicular to the oxygen planes.

Dramatic Changes in Thermoelectric Power of Germanium under Pressure: Printing n-p Junctions by Applied Stress.

Controlled tuning the electrical, optical, magnetic, mechanical and other characteristics of the leading semiconducting materials is one of the primary technological challenges. Here, we demonstrate that the electronic transport properties of conventional single-crystalline wafers of germanium may be dramatically tuned by application of moderate pressures. We investigated the thermoelectric power (Seebeck coefficient) of p- and n-type germanium under high pressure to 20 GPa.

Tuning the electronic and vibrational properties of SnPSe and PbPS crystals and their metallization under high pressure.

External stimuli enabling either a continuous tuning or an abrupt switching of the basic properties of materials that are utilized in various industrial appliances could significantly extend their range of use. The key characteristics of semiconductors are basically linked to their electronic and optical properties. In this study, we experimentally demonstrated that two kindred wide-band-gap semiconductors, ferroelectric SnPSe and paraelectric PbPS, which are commonly used in optical technologies, have remarkably different and unusual responses in their electronic band structures to applied moderate pressures.

A hard oxide semiconductor with a direct and narrow bandgap and switchable p-n electrical conduction.

An oxide semiconductor (perovskite-type Mn2 O3 ) is reported which has a narrow and direct bandgap of 0.45 eV and a high Vickers hardness of 15 GPa. All the known materials with similar electronic band structures (e.