X-ray emission spectra and structural models of BCN materials

The results of measurements of BKalpha, NKalpha and CKalpha (ultra-soft X-ray emission spectra of boron carbonitride phases synthesized by nitridation of boron carbide at 1200, 1800 and 24 000 degrees C) are presented. The obtained results are compared with spectra of reference compounds (a-B, B4C, BN and graphite). It was found that BKalpha and NKalpha spectra of carbonitride phases were identical to that of BN. On the other hand, CKalpha spectra of the BCN system were very similar to that of graphite. No trace of B-C chemical bonding was found for BCN compounds. The obtained results confirm the structural model of the ternary compound according to which separate boron nitride and graphite layers are in random intercalation.</p

Synthesis, structure, and XPS characterization of the stoichiometric phase Sr2CuO2F2

Thermogravimetric analysis has revealed that reduction of Sr2CuO2F2+δ in 10% H2/90% N2, occurs in two distinct steps on heating up to 930 °C. Whereas reduction to give SrF2, SrO, and Cu is complete above 800 °C, a stable intermediate forms in the region between 250 and 450 °C. This has been identified as a new tetragonal (I4/mmm) phase, Sr2CuO2F2, with unit-cell dimensions a = 3.967(1) Å and c= 12.816(2) Å. The structure has been determined from powder x-ray-diffraction data and is related to Nd2CuO4 (T′'-type). Madelung energy, bond valence sum calculations, and F 1 s-XPS data clearly indicate that the F- ions occupy sites within the fluorite block (Sr2F2) insulating layers. This contrasts with the La2CuO4 (T-type) structure which is adopted by Sr2CuO2F2+δ-

Electronic structure of VO2 studied by x-ray photoelectron and x-ray emission spectroscopies

A VO2 single crystal has been the subject of a combined investigation by high-resolution x-ray photoelectron spectroscopy (XPS), x-ray emission spectroscopy (XES) with both electron and energy-selective x-ray excitation (V L alpha, V K beta(5) and O K alp</p