Determination of Bi in complex oxide samples by atomic absorption spectrometry by using ordinary acetylene – air flame atomization

In the present work the air/acetylene flame atomic absorption spectrometry was used for bismuth determination in complex oxides. Interference studies were carried out, and interference with vanadium and molybdenum was detected. The method of standard additions and traditional calibration curve method were used. Calibration and standard addition curves were fitted with linear and polynomial functions. It was shown that using polynomial function gives better results for the standard additions method for determination of bismuth by acetylene/air flame atomic absorption spectrometry. The calibration curve method was shown to be correct at low ( 10mg/L) concentration of an interferent

Comparative characteristic of Bi- and La- doped (Ca/Sr)MoO4 -based materials with a defect scheelite-type structure

CaMoO4- and SrMoO4-based scheelite-type phases are noteworthy functional materials, whose properties strongly correlate with their structure. This work is devoted to La- or Bi-doped scheelite-type molybdates. The purpose of the present study is to quantify the effect of isolated electron pairs of bismuth on the distortion of the structure and related properties. Conventional solid-state technology was used for the synthesis of (Ca/Sr)1–3xLa2xФxMoO4 and Sr1–3xBi2xФxMoO4, (0.025≤ x ≤ 0.275). The structure was investigated by X-ray powder diffraction and Raman spectroscopy. Rates of structure distortion were characterised by the analysis of the autocorrelation function (AAF) of Raman spectra. Energy gaps were calculated by the Kubelka-Munk method. The conductivity was studied with a.c. impedance spectroscopy. For (Ca/Sr)1−3x(Bi/La)2xФxMoO4 series 0.025 ≤ x ≤ 0.15 compositions show a basic defect scheelite structure, while 0.15 x ≤ 0.225 compositions of Bi-doped samples exhibit tetragonal supercells. The chemical compression of unit cell is more evident in the case of Bi-doping, indicating the preferred orientation of the isolated electron pairs. The distortion of MoO4 polyhedra showed by AAF was more significant for Sr1−3xBi2xФxMoO4 than for Sr1−3xLa2xФxMoO4, the Δcorr parameters for Bi-doped compositions were almost double in comparison with La-doped one in the range of 50–600 cm–1 of the Raman shift. The «critical» x = 0.15 point was also clearly indicated by Δcorr parameter. The AAF of the Raman spectra of solid oxides was shown to be a good tool for prediction of properties and points of phase transitions in solid oxides

Structure and microwave dielectric properties of Bi- and Ge-doped calcium molybdate

The powders of Ca1–2xBi2xMo1–xGexO4 solid solutions weresynthesized by the conventional solid state method and investigated by X–ray powder diffraction and Raman spectroscopy. The Ca1–2xBi2xMo1–xGexO4 compositions crystallize in scheelite structure (sp. gr. I41/a) at 0 x  0.4, but traces of bismuth germanates are detected by scanning electron microscopy. The x = 0.5 composition contains several phases with BiVO4- type structures. Raman spectroscopy detected the deformation of [BO4]2– polyhedra and changes in B–O bond length (B = Mo, Ge). The energy gaps were calculated from the diffuse scattering spectra by the Kubelka-Munk method. Energy gap (Eg) values decrease with x from 3.29 eV to 2.91 eV, probably due to 6s2 electrons of bismuth in the valence band and changes of the conductivity band by electrons of germanium. Such values of Eg can provide photocatalytical activity of powders under UV and visible light. The electrodynamic parameters of the ceramic sample of Ca1–2xBi2xMo1–xGexO4 were measured by the transmission line method. The average permittivity increases with x from ~10 to ~18 which correlates with theoretical ε, Vmol and total polarizability of samples. An increase in the concentration of bismuth and germanium leads to the additional resonant peaks in the spectra of ε, S11 and S21. These resonant peaks can be probably caused by the appearance of irregular structural domains of Bi atoms or induced by the increased size of grains in the ceramic samples