Аннотация:We have developed an approach for joint determination of La, Fe, and Sr in solutions and suspensions of (La,Sr)FeO3 composites by total reflection X-ray fluorescence (TXRF) spectroscopy with the aim of assessing the effect of strontium substitution for lanthanum on the gas-sensing properties of lanthanum ferrites. A gallium solution with a concentration of 50 mg/L was used as an internal standard for determination of the constituent elements. The adequacy of the results obtained was ascertained using inductively coupledplasma atomic emission spectroscopy (ICP AES) of solutions of the samples. According to the data weobtained, there were no interelement effects when La, Fe, and Sr were present together in solution. The reproducibility of the TXRF determination results (Sr) was 0.04, 0.05, and 0.06 for La, Fe, and Sr, respectively. The reproducibility of the results for the suspensions was due to the small particle size (15–17 nm) and the uniform distribution of the internal standard in the aliquot in the sample preparation procedure chosen. All of the materials were shown to consist of a single phase, corresponding to pure lanthanum ferrite with an orthorhombic crystal lattice (ICDD card no. 37-1493). The absence of unindexed reflections in their X-ray diffraction patterns points to successful incorporation of Sr2+ cations into the La3+ site. Doping of lanthanum ferrite with strontium was shown to improve the sensitivity of the materials to CO, NH3, methanol, and acetone and reduce the optimal working temperature of the sensor by 50–150°C. The best gas-sensing properties were offered by the lanthanum ferrite nanofiber containing the lowest Sr concentration (0.01 at %). At thesame time, the insensitivity of the materials to methane and benzene is the result of the higher stability of their molecules to acid–base active surface centers of La1 – xMexFeO3.
