Core level photoemission spectroscopy and chemical bonding in Sr2Ta2O7.

Electronic parameters of constituent element core levels of strontium pyrotantalate (Sr2Ta2O7) were measured with X-ray photoelectron spectroscopy (XPS). The Sr2Ta2O7 powder sample was synthesized using standard solid state method. The valence electron transfer on the formation of the Sr–O and Ta–O bonds was characterized by the binding energy differences between the O 1s and cation core levels, Δ(O–Sr) = BE(O 1s) − BE(Sr 3d5/2) and Δ(O–Ta) = BE(O 1s) − BE(Ta 4f7/2). The chemical bonding effects were considered on the basis of our XPS results for Sr2Ta2O7 and earlier published structural and XPS data for other Sr- and Ta-containing oxide compounds. The new data point for Sr2Ta2O7 is consistent with the previously derived relationship for a set of Sr-bearing oxides. The binding energy difference Δ(O–Sr) was found to decrease with increasing bond distance L(Sr–O). © 2009, Elsevier Ltd

Crystal growth and electronic structure of low-temperature phase SrMgF4

Using the vertical Bridgman method, the single crystal of low temperature phase SrMgF4 is obtained. The crystal is in a very good optical quality with the size of 10×7×5 mm3. Detailed photoemission spectra of the element core levels are determined by a monochromatic AlKa (1486.6 eV) X-ray source. Moreover, the first-principles calculations are performed to investigate the electronic structure of SrMgF4. A good agreement between experimental and calculated results is achieved. It is demonstrated that almost all the electronic orbitals are strongly localized and the hybridization with the others is very small, but the Mg–F bonds covalency is relatively stronger than that of Sr–F bonds. © 2015 Elsevier B.V