Results
X-ray powder diffraction (XRD) patterns were recorded by a D8 Advance (Bruker) with Cu Kα (wavelength 1.54 Å) after nanoparticles were calcined at 600 °C for 2 hours. SEM (FEI Company, USA-Quanta 200) was used to investigate the morphology, size, and uniformity of the products. A particle size analyzer was used to illustrates the size distribution. During the PSA test, the ethanol was used as a dispersant, temperature was set at 25 °C, and the test duration was 50 s.
The powder XRD data are shown in Fig.1(a-b) and Fig.2(a-b), indicates the crystalline structure of the as-synthesized perovskite-type oxide nanoparticles obtained using the sol-gel auto-combustion method. The ratio of fuel to oxidizer (F/O), and using different fuel in this method, causes the changes crystalline properties and purity of the final product. However, XRD patterns of all samples exhibited diffraction peaks of LaCoO3 (JCPDS No.-01-084-0848), irrespective of the F/O ratio and fuel. But the existence of impurity was observed and discussed as follows. Fig.1(a-b) shows the XRD patterns of sample LCG1 and LCG2 respectively. As illustrated in Fig.1-a, by using glycine in the ratio of F/O=1, the mixture of the cobalt oxide (CoO, Co3O4), lanthanum oxide (La2O3), La(OH)3 and perovskite phase obtained, but Fig1-b shows the purity of perovskite phase. It was shown strong peaks at 32.9° (110) and 33.3° (104), and the peaks observed around 32°, 60° and 70° are bifurcated which is the characteristic peak for the rhombohedral structure and also indicated no trace of CoO, Co3O4, La(OH)3 or La2O3, which corresponded to the high degree of La and Co oxide incorporation into the perovskite structure achieved by glycine as fuel and F/O=2. Furthermore, Fig.2 (a-b) shows that using urea as fuel can cause changes in purity and crystalline properties also. The production of LaCoO3 nanoparticles, with Co3O4 and La2O3 as impurities by using both F/O=1 and 2 was achieved. However, it can be concluded that higher ratio of glycine causes complete oxidation while urea in low ratio and high ratio cause partial oxidation and lower degree of La and Co oxide incorporation into the perovskite structure.