Low temperature sintering of Ba(Zr0.8−xCexY0.2)O3−δ using lithium fluoride additive

Abstract

Lithium fluoride (LiF) was selected as a liquid phase sintering additive to lower the sintering temperature. The effects of LiF on the sinterability, microstructure, and electrochemical properties of Ba(Zr 0.8 − x Ce x Y 0.2 )O 3 − δ (0≤ x ≤ 0.4) (BZCYs) ceramics were investigated. Using LiF as an additive, high density BZCYs ceramics can be obtained at sintering temperatures 200-300°C lower than the usual 1700°C with much shorter soaking time.Nuclear reaction investigations showed no lithium and a small amount of fluorine reside in the sample which indicates the non-concomitant evaporation of lithium and fluorine during the sintering process. Scanning electron microscopic investigations showed the bimodal structure of BZCYs ceramics and grain growth as Ce content increases. In a water saturated hydrogen containing atmosphere, BZCYs ceramics have higher conductivity when LiF is used in the sintering process. LiF-added BZCYs electrolyte-supported fuel cells with platinum electrodes were tested at temperatures from 500 to 850°C. Results show that LiF is an excellent sintering additive for lowering the sintering temperature of BZCYs.

Effect of lithium fluoride on thermal stability of proton-conducting Ba(Zr0.8−xCexY0.2)O2.9 ceramics

“…In the recent study by Tsai et al [22], nuclear reaction analysis (which is sensitive to elemental concentration) showed negligible residue of Li in 7 wt.% LiF-added BZCY622 solid ceramic after sintering at 1400°C for various dwell times [22]. The 7 wt.% LiF-addition does not reduce conductivity, but rather slightly improves the total Post XRD spectra of LiF-added BZCY712 and BZCY622 (a and d) after calcining at 1200°C in air for 5 h, (b and e) after subsequent exposure to CO 2 at 850°C for previously calcined powders at 1200°C for 5 h, and (c and f) after calcining at 1400°C in air for 5 h. "+" and "#" indicate BaCO 3 and Y 2 O 3 -like structure, respectively.…”

“…"□" represents possibly high-cerium BZCY. conductivity of BZCY (x = 0.0-0.4) ceramics measured at 700°C in a water saturated 4% H 2 + 96% Ar atmosphere [22].…”

“…Lithium fluoride (LiF) has been used as a sintering aid to reduce the sintering temperature and also to enhance density in SOFC ceramics [22]. However, there is not much knowledge on the effects of adding LiF on thermal stability under CO 2 atmosphere.…”

Chemically stable Dy–Y double substituted barium zirconate with high proton conductivity and improved sinterability

“…Prolonged sintering at high temperatures, although may result in a product with higher density and larger grain sizes but often also result in lowered bulk conductivities because of barium deficiency and creation of cation non-stoichiometry in the sintered compound [17,18]. Recently different processing approaches such as reactive sintering, introduction of sintering aids such as ZnO, CuO, NiO or LiF or their combination were introduced as promising methods for fabrication of barium zirconate-based compounds with both high bulk conductivity and large grains, leading to a high total conductivity [19][20][21][22][23][24]. However, the stability of the transition metal oxides under reducing atmosphere and their impact on the ionic transfer is under question and has not been explored yet.…”

Effect of Sintering Temperature on Microstructure and Hydrogen Permeation Properties of Perovskite Membrane

“…Wang et al [19] studied the effect of sintering temperature in Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3Àd membranes for O 2 separation. Tsai et al [20] worked on BaCeYO membrane and showed good results for H 2 separation. However, there are no major reports about the effect of the sintering parameters, such as temperature and dwell time, on the microstructure of membranes and their influence on permeation flux in hydrogen separation, and therefore it seems to be necessary to focus our attention in this field.…”