Structural analysis and sintering aids effects in La2Ce2O7 proton conductors

Zamudio-García, Javier; Porras-Vázquez, José Manuel; Losilla, Enrique R.; Marrero-López, David

Abstract

Global warming is an important problem that has to be solved without delay. The development of environmental-friendly energy technology is needed to deal with this issue. Solid Oxide Fuel Cells (SOFC) technology has been proposed as a real alternative to fossil fuel combustion. Proton conductors like La2Ce2O7 (LDC), has several advantages in comparison with BaCeO3 due to its high stability in H2O or CO2 conditions [1]. Furthermore, for industry application is necessary to low the high sintering temperature of typical electrolyte materials. La2Ce2O7 was synthesized by the freeze-drying precursor method and calcination conditions have been optimized to obtain single phase with high compaction at 1400 ºC for 1h. A fully characterization has been carried out using X-ray powder diffraction and scanning electron microscopy. The total conductivity was determined by complex impedance spectroscopy in dry and wet air. Transmission Electron Microscopy (TEM) was used to clarify certainly the structure of La2Ce2O7 due to its still unknown. SAEDs patterns revealed a disordered fluorite, not appearing secondary reflections typical of pyrochlore superstructure, finishing the controversy around the correct structure in this material [2,3]. Moreover, an exhaustive study about lowering the sintering temperature with Co and Zn as sintering aids has been investigated obtaining electrolytes that can be used for SOFC. The sintering aids were impregnated using cobalt and zinc nitrates in ethanol media. Both sintering aids allow for obtain high dense pellets lowering the sintering temperature 300 ºC and 400 ºC for samples with cobalt and zinc, respectively, without compromising the electrical and microstructural properties (Fig 1).

Structural analysis and sintering aids effects in La2Ce2O7 proton conductors

Author: Zamudio-García, Javier,Porras-Vázquez, José Manuel,Losilla, Enrique R.,Marrero-López, David

Year: 2018

Source: https://riuma.uma.es/xmlui/bitstream/10630/16891/1/XVSJIQ_ZamudioGarc%c3%adaJavier.pdf

XV Simposio de Jó enes In es igado es Químicos
(Toledo, 2018)
STRUCTURAL ANALYSIS AND SINTERING AIDS EFFECTS IN La2Ce2O7
PROTON CONDUCTORS
J. Zamudio-Ga cía1, J.M. Po as-Vázquez1, En ique R. Losilla1, D. Ma e o-López2.
1 Uni e sidad de Málaga, Dp o. de Química Ino gánica, C is alog a ía y Mine alogía, 29071-Málaga,
Spain, z[email p o ec ed]
2 Uni e sidad de Málaga, Dp o. de Física Aplicada I, 29071-Málaga, Spain.
Global wa ming is an impo an p oblem ha has o be sol ed wi hou delay. The
de elopmen o en i onmen al- iendly ene gy echnology is needed o deal wi h his
issue. Solid Oxide Fuel Cells (SOFC) echnology has been p oposed as a eal al e na i e
o ossil uel combus ion. P o on conduc o s like La2Ce2O7 (LDC), has se e al ad an ages
in compa ison wi h BaCeO3 due o i s high s abili y in H2O o CO2 condi ions [1].
Fu he mo e, o indus y applica ion is necessa y o low he high sin e ing empe a u e
o ypical elec oly e ma e ials.
La2Ce2O7 was syn hesized by he eeze-d ying p ecu so me hod and calcina ion
condi ions ha e been op imized o ob ain single phase wi h high compac ion a 1400 ºC
o 1h. A ully cha ac e iza ion has been ca ied ou using X- ay powde di ac ion and
scanning elec on mic oscopy. The o al conduc i i y was de e mined by complex
impedance spec oscopy in d y and we ai . T ansmission Elec on Mic oscopy (TEM)
was used o cla i y ce ainly he s uc u e o La2Ce2O7 due o i s s ill unknown. SAEDs
pa e ns e ealed a diso de ed luo i e, no appea ing seconda y e lec ions ypical o
py ochlo e supe s uc u e, inishing he con o e sy a ound he co ec s uc u e in his
ma e ial [2,3].
Mo eo e , an exhaus i e s udy abou lowe ing he sin e ing empe a u e wi h
Co and Zn as sin e ing aids has been in es iga ed ob aining elec oly es ha can be used
o SOFC. The sin e ing aids we e imp egna ed using cobal and zinc ni a es in e hanol
media. Bo h sin e ing aids allow o ob ain high dense pelle s lowe ing he sin e ing
empe a u e 300 ºC and 400 ºC o samples wi h cobal and zinc, espec i ely, wi hou
comp omising he elec ical and mic os uc u al p ope ies (Fig 1).
Figu e 1. Nyquis diag ams and SEM mic og aphs o selec ed samples o LDC, LDC-Co and LDC-Zn.
Re e encias
[1] Z. Zhu, B. Liu, J. Shen, Y. Lou, Y. Ji Jou nal o Alloys and Compounds. 2016, 659, 232-239
[2] J. Sung Bae, W. Kil Choo, C. Hee Lee, J. Eu . Ce am. Soc. 2004, 24, 1291-1294.
[3] D. Vanpoucke, P. Bul inck, S. Co enie , V. Van Speyb oeck, I. Van D iessche, Phys. Re . B 2011, 84,
054110.
2 µm
La2Ce2O7-Zn
0.7 µm
2 µm
La2Ce2O7-Co
0.4 µm
1000 °C-5h 1100 °C-5h
0100 200 300 400 500 600
0
-150
-300
La2Ce2O7
La2Ce2O7-Co 1100-5h
La2Ce2O7-Zn 1000-5h
Z (kΩ·cm)
350000 400000 450000
0
-50000
La2Ce2O7
La2Ce2O7-Co 1100-5h
La2Ce2O7-Zn 1000-5h
Z (kΩ·cm)
0150000 300000 450000
0
-100000
-200000
La2Ce2O7
La2Ce2O7-Co 1100-5h
La2Ce2O7-Zn 1000-5h
0150000 300000 450000
0
-100000
-200000
La2Ce2O7
La2Ce2O7-Co 1100-5h
La2Ce2O7-Zn 1000-5h
0200000 400000 600000
0
-100000
-200000
-300000
La2Ce2O7
La2Ce2O7-Zn 1100-5h
La2Ce2O7-Zn 1000-5h