Processing-induced secondary phase formation in Mo-substituted lanthanum tungstate membranes

Structural and Transport Properties of E-Beam Sintered Lanthanide Tungstates and Tungstates-Molybdates

“…Similar to CS samples with the same compositions [24], it is apparently related to faster oxygen diffusion along grain boundaries for the NWMO sample compared with that of other samples (Table 4). This can be explained by the difference in the W-O and Mo-O binding energy as well as the effect of the Mo cation on the extended defect features, such as oxygen vacancy ordering or clustering [37,38], thin secondary phase film segregation along grain boundaries [39,40] and the probable effect on the porous structure [41]. At temperatures above 500 • C, the behavior of the isotope exchange process is almost the same for all three samples (Figure 7).…”

Rare Earth Tungstate: One Competitive Proton Conducting Material Used for Hydrogen Separation: A Review

“…When x = 1, the formula is La 27 W 5 O 54+3/2 v 1/2 (La/W = 5.4, LWO54), each formula unite accommodates one W in La2 sites, and the number of oxygen vacancies is 1/2. The existence of W at La2 sites was confirmed by many subsequent experiments [44][45][46]. LWO54 was proved to be a stable composition.…”

Direction observation of the grain boundary segregation in molybdenum substituted lanthanum tungstate membranes

“…1a, the LWO-Mo membranes show compact grains, with various sizes ranging from several µm to tens of µm. 28,29 The XRD result reveals that the LWO-Mo is predominantly composed of grains with the LWO fluorite structure (see Fig. S1 in the ESI †).…”

“…Challenges to directly investigate these nanograins down to atomic scale include their limited sizes especially in the direction vertical to the interface, their different orientations comparing with the neighboring LWO-Mo grains, and the common overlap of three components (the nanograin and the two LWO-Mo grains) along the viewing direction. Meanwhile, for the investigated membranes, in addition to the primary LWO-Mo phase, a few secondary phase (SP) grains were occasionally located 29 (see Fig. S4 in the ESI †).…”