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

Abstract

Lanthanide tungstates and molybdates are promising materials for hydrogen separation membranes due to their high protonic conductivity. A promising approach to fabricating ceramics based on these materials is radiation thermal sintering. The current work aims at studying the effect of radiation thermal sintering on the structural morphological and transport properties of (Nd,Ln)5.5(W,Mo)O11.25–δ as promising materials for hydrogen separation membranes. The defect fluorite structure was shown to be preserved during radiation thermal sintering at 1100 °C. The presence of protons in hydrated samples was confirmed by TGA. According to four-electrode studies and the isotope exchange of oxygen with C18O2, the samples demonstrate a high proton conductivity and oxygen mobility. Residual porosity (up to 29%) observed for these samples can be dealt with during membrane preparation by adding sintering aids and/or metal alloys nanoparticles. Hence, sintering by e-beams can be applied to the manufacturing of hydrogen separation membranes based on these materials.

Synthesis and Oxygen Mobility of Bismuth Cerates and Titanates with Pyrochlore Structure

“…Conventionally sintered bismuth titanates’ samples have larger particles compared to the samples after RTS at 1100 °C ( Figure 6 ). A similar tendency was demonstrated in [ 37 ] for lanthanide tungstates and molybdates. Using the traditional sintering of bismuth titanate at 1100 °C, the average grain size ranges from 1 to 10 microns.…”

“…Hence, it was demonstrated that RTS allows for carrying out sintering processes for shorter times and at lower temperatures compared to those for conventional sintering. Such a difference in sintering temperature and duration required to obtain the desired gas-tightness for radiation–thermal sintering and conventional sintering is apparently related to the dissipation of radiation energy in heterogeneous structures, thermal-diffusional stimulation of mass transfer, and other features of the RTS process [ 37 ].…”

“…With traditional thermal sintering in a furnace, long-term processing, and high temperatures are required to obtain ceramics with desired properties, such as gas tightness, homogeneous phase composition, etc. To solve this problem, radiation-thermal sintering (e-beam processing) is proposed [ 37 , 38 , 39 , 40 , 41 ]. Using the main advantages of radiation-thermal reactions—lowering the treatment temperature and a high reaction rate—will reduce the processing time while also significantly reducing internal thermal stresses.…”

“…structures or their nanocomposites, such as LFN-GDC, LFC-GDC, La 0.3 Bi 0.7 MnO x –Bi 1.5 Y 0.3 Sm 0.2 O 3 , etc.) using unique equipment of the Budker Institute of Nuclear Physics [ 37 , 38 , 39 , 40 , 41 ]. Disordering of nanodomains by electron beams leads to their easy sintering at moderate temperatures without increasing their sizes.…”

“…Disordering of nanodomains by electron beams leads to their easy sintering at moderate temperatures without increasing their sizes. This results in a developed network of domain boundaries, which, for nanocomposites [ 37 , 38 , 39 , 40 , 41 ] or even some complex oxides (such as molybdates of lanthanoids [ 42 ], etc. ), provide fast oxygen diffusion channels described by the so-called 2D model of oxygen diffusion.…”