Characterization and Rietveld refinements of new dense ceramics Ba_3−xSr_xTb_3−xCe_xO₉ (x = 1 and 1.5) perovskites

Abstract

Ba3−xSrxTb3−xCexO9 (x = 1 and 1.5) ceramics (BSTC) with a relative density of 93% and a grain size distribution of 0.2–3 µm were prepared by the mixed-oxides reaction route. The crystalline structures, microstructures, valence states, and electrical properties of two ceramics were analyzed using X-ray powder diffraction (XRPD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), and electrical measurements. Rietveld analyses of XRPD patterns show that BSTC1 is indexed as a trigonal structure with the space group R-3c, and BSTC3/2 is indexed as an orthorhombic perovskite structure with the space group Pmcn. The EPR, XPS, and electrical conductivity results confirm that Ce and Tb ions in BSTC exist as Ce4+ and mixed-valence states of Tb4+/Tb3+, respectively. At room temperature, the two BSTC ceramics exhibit a similar semiconducting behavior. The relationships between electrical conductivity and temperature/frequency are provided. The defect chemistry is discussed.

A new class of ion substitution to achieve high electrostrain under low electric field in BNT‐based ceramics

“…It has been reported that the satellite peak located at 916.7 ± 0.7 eV is a fingerprint of Ce with +4 oxidation state. 26 The multiple deconvolution peaks are related to Ce 3d 5/2 and Ce 3d 3/2 spin orbit splitting accompanied by their satellite peaks with the presence of +3 and +4 oxidation states of Ce, and their binding energies can refer to previous literatures. 25 In addition, the peak area percentage of Ce 4+ has a sudden reduction from 70.6% at x = 0.5 to 63.3% at x = 0.75, and further drops to 47.7% at x = 1.5 as compared in the histogram in Figure 3C.…”

“…No references were found on modeling of the PIP process for CMCs, though experimental studies on this manufacturing process have been reported. Studies on polycarbosilanederived SiC ceramic 25 and SiC/SiC composite 26,27 have shown that porosity decreases and mechanical properties improve with the increasing number of PIP cycles. Zhu et al 28 show that increasing pyrolysis temperature and the concentration of SiC fillers in polycarbosilane polymer result in improved mechanical properties in two-dimensional Carbon/ SiC (C/SiC) composites fabricated using the PIP process.…”

NiO / Sr doped Ce0.85Pr0.10 Er0.05O2-δ mesoarchitectured catalyst for partial oxidation of CH4 and anode fueled by H2

“…At intermediate temperatures the high electrode overpotential as well as the increased resistance of electrolyte still remain shortcomings for this kind of fuel cells. The overcoming could be realized by using an electrolyte with a decreased thickness or using an electrolyte with high ionic conductivity such as cerates [7] type. Due to their tunable ionic conduction behavior, high oxygen storage capacity and the satisfactory thermal and mechanical resistance, doped-CeO2 materials have been widely studied as component of SOFC directly operated with hydrocarbon fuels.…”