The preparation technique during synthesizing process and heat treatment plays an important role in the properties of the ceramic materials. In this paper, ceramic perovskite-type oxide based on Ba (Ce,Zr)O3 was prepared by sol-gel method and sintered via two-step sintering (TSS) technique. In the TSS, the sintered pellet was undergoing twice heat treatment. The first temperature profile was set at T1= 1400°C and the second temperature were varied at T2 = 1150°C, 1200°C, 1300°C and 1350°C, respectively. XRD results showed that all samples TSS1 to TSS5 exhibit single-phase of cerate-zirconate ceramics except for the pellet sintered at 1300°C (TSS4). The crystalline peaks for single-phase sintered pellets were matched to the standard compound Ba(Ce,Zr)O3 . On the other hand, the presence of secondary phases of CeO2 , Ba2ZrO4 and BaCO3 along with the main phase of Ba(Ce,Zr)O3 were detected in TSS4. SEM analysis revealed that the samples formed clear and compact grains with submicron sizes whereby the size of grain decreased from 336.4 to 192 nm as the second sintering temperature increased. This paper attempts to show that the implementation of different sintering profile in TSS method was found to give significant effect on the phase and morphology of solid solution of Ba(Ce,Zr)O3 .
The application of La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) as a potential cathode working on a BaCe0.54Zr0.36Y0.1O2.95 (BCZY)
electrolyte for proton conducting solid oxide fuel cell was investigated. LSCF nanoceramic powders were synthesized by
an activated carbon-assisted sol-gel process using metal nitrate-based chemicals. The LSCF powder was transformed to a
slurry and spin-coated onto both surfaces of BCZY pellet to form a symmetrical cell with the configuration of LSCF|BCZY|LSCF.
The symmetrical cell was subsequently sintered at 950°C for 2 h to allow a good contact formation between electrode/
electrolyte layers. The phase structural verification of the calcined powders was investigated by X-Ray diffractometer
(XRD). Field-emission scanning electron microscopy (FESEM) was employed to examine the morphology of the sintered
cell. The electrochemical behaviour of the symmetrical cell was studied by an electrochemical impedance spectroscopy.
The formation of a single perovskite LSCF phase with a crystallite size of 20 nm was obtained at 700°C as corroborated
by XRD analysis. The FESEM images showed a good contact between LSCF cathode and BCZY electrolyte at electrode/
electrolyte interfacial layer. The ASR obtained for LSCF symmetrical cell measured at 700°C with and without Pt current
collector is 0.87 and 31.25 Ωcm2, respectively.
The BaCe0.95Yb0.05O2.975 compound was successfully prepared by the sol-gel method using metal acetate salts as starting materials. Fourier transform infrared (FTIR) results showed that the carbonate ions residue almost disappeared at calcination temperature of 1300 oC. Particles size of the final calcined powder obtained from particle size distribution was in the range of 300-450 nm. Diameter of grains for the sintered pellet (relative density ≈85 %) obtained from scanning electron microscope was between 2-5 μm. It is interesting to note that eliminating the carbonate ions residue enhanced the mechanical and chemical stability of the sample.
Ceramics powder of BaCe0.54Zr0.36Y0.1O2.95 (BCZY) was synthesized using three different methods namely sol-gel (SG), supercritical fluid (SC) and supercritical fluid assisted sol-gel (SCSG). The respective prepared samples were denoted as S1, S2 and S3. TG thermogram of the dried powders for all samples showed three stages of weight loss. Each stage was corroborated by one or two exothermic peaks as shown in DTG signal. Complete thermal decomposition for all the samples was almost accomplished at 1000°C for about 2 h. At calcination temperature of 1100°C, S1 showed a single-phase of perovskite-type oxides as proven by XRD result. Morphology of the calcined powders by SEM micrograph showed that S1 is in spherical shape, S2 is in cubic structure and S3 has a mixture of spherical and rod-like structure. Therefore, as comparison, SG method gives better characteristics of cerate-zirconate ceramics powder compared to SC and SGSC.
A nitrate-based nickel salt was used to prepare NiO-BaCe0.54Zr0.36Y0.1O2.95 (NiO-BCZY) composite powders by an evaporation
and decomposition of solution and suspension (EDSS) method. The prepared powders with different weight ratios of NiO to
BCZY (NiO:BCZY) were denoted as S1 (50:50) and S2 (60:40). The powders were characterized using Thermogravimertic
analyzer (TGA), X-ray diffractometer (XRD) and scanning electron microscope (SEM) equipped with energy dispersive
X-ray (EDX) spectrometer. TGA results showed that the thermal decomposition of intermediate compounds in the dried
powder (T = 150°C) completed at ~700°C. XRD analysis confirmed that the calcined powder (T = 1100°C) of S1 and
S2 did not show any crystalline peaks related to BCZY compound as the peaks associated to impurity phases of BaCeO3
and BaZrO3
were appeared in their XRD patterns. The impurity phases along with NiO still remained in the S1 sample
after it was calcined at 1400°C. As the calcination temperature increased, the particles size of S1 also increased and Zr
elemental composition deviates from the nominal stoichiometric of the NiO-BCZY as proven by SEM/EDX analysis. The
results indicate that the formation of homogenize NiO-BCZY composite prepared using EDSS method was not favored even
after calcined at high temperature (T = 1400°C).