О возможности введения примеси железа в узлы A в SrTiO-=SUB=-3-=/SUB=-

The local environment and oxidation state of the Fe impurity in strontium titanate are studied using XAFS spectroscopy. The influence of annealing temperature and deviation from stoichiometry on the possibility of incorporation of the impurity into the A and B sites of the perovskite structure is studied. The results obtained from the X-ray diffraction, XANES spectra, and EXAFS spectra suggest that at high annealing temperature the iron atoms, at least partially (up to 30%), enter the A sites in SrTiO3. The obtained results agree with results of first-principles calculations, according to which the iron at the A site exhibits strong off-centering (the displacement of ~1 Angstrom), similar to that previously established in SrTiO3 samples doped with Mn and Co.

DETERMINATION OF ULTRA-SMALL DEVIATIONS FROM STOICHIOMETRY BY EQUILIBRIUM VAPOR PHASE COMPOSITION OF WIDE BEND GAP А2 В6 SEMICONDUCTORS

The paper considers the possibility of determining the deviation from the stoichiometry in cadmium and zinc chalcogenides by the composition of the equilibrium vapor phase. The conditions for the evaporation are considered. It is shown that if the ratio of the of the solid and vapor phases volumes is more then 120, it is possible to determine the deviation from stoichiometry at the order of magnitude 1014 cm-3.

Nature of thermoelectric properties occurring in defected Sn2P2S6 chalcogenide crystals

Detailed first-principles calculations were performed to explain the physical nature of the thermoelectric properties occurring in Sn2P2S6 (SPS) crystals with deviation from stoichiometry.

Исследование длинноволновых инфракрасных спектров отражения моно- и поликристаллов SmS в области гомогенности

The far- and mid-IR reflection spectra of Sm_1 + x S ( x = 0–0.17) samples are recorded and analyzed, as well as their electrical and structural parameters at a temperature of T = 300 K. The bond ionicity in SmS is shown to fall with a decrease in the area of the X-ray coherent scattering region and an increase in the concentration of donor impurities and, consequently, conduction electron concentration. The electrical conductivity of stoichiometric SmS single crystals and polycrystals can be determined with an error of 10% from the IR reflection spectra. Due to the low structural quality of the samples, the electrical conductivity cannot be determined in the case of deviation from stoichiometry.

Изоэлектронные центры кислорода и проводимость кристаллов CdS в сравнении с PbS

The influence of oxygen on the electrical properties of PbS are well known. The goal of this study is to compare and reveal this phenomenon in CdS(O) single crystals, which we have studied in detail previously. The experiments are performed for CdS single crystals with a known oxygen concentration, deviation from stoichiometry, and definite set of intrinsic point defects. They allow us to confirm the results described for PbS and clarify their nature. It is shown that the phenomenon is based on the capture of free charge carriers— electrons—by acceptor-like isoelectronic O_S centers with the subsequent formation of associates having a complex structure. Previous conclusions on the dissolution mechanism of oxygen in CdS with deviations from stoichiometry are confirmed. Variations in the electrical properties in oxygen-activated PbS(O), similarly to CdS(O), showed that isoelectronic oxygen centers O_S are present in lead sulfide.