Synthesis of La1-xSrxCoO3-δ and its REDOX performance in air

Abstract

In recent years, perovskite oxides, as one of the potential thermochemical energy storage materials, have attracted much attention from researchers. Studies have shown that doping other elements in perovskite oxides can reduce the molecular weight of perovskite and even improve the thermochemical energy storage performance of perovskite material. Used sol-gel method in this paper to prepare a series of Sr doped LaCoO3 samples (La1−xSrxCoO3-δ, x = 0, 0.1,0.3, 0.5, 0.6, 0.7, 0.8, 0.9). The effects of calcination temperature, types of complexing agent and Sr doping amount on the synthesis and REDOX property in air of La1−xSrxCoO3-δ perovskite oxides were investigated. The crystal phase structures, microstructure, chemical states, specific surface area and the REDOX cycle reversibility and stability of perovskite samples were tested by XRD, SEM/EDS, XPS, BET and STA. Three types of complexing agent are sucrose plus glycol, citric acid plus glycol, sucrose without glycol, and the three groups of samples are recorded as S+E method samples, C+E method samples and S method samples. When the calcination temperature of both S+E method samples and C+E method samples was low, there were more impurities in the samples. Impurities adversely affected the cyclic stability and reversibility of the samples. Materials with higher purity and better REDOX performance were obtained by calcinating at higher temperature. Through strontium doping, LaCoO3 possessed the potential to store energy in air. The higher the Sr content in the sample and the lower the calcination temperature can make it obtain a larger specific surface area. Among the samples, La0.2Sr0.8CoO3-δ has the highest oxygen vacancy content and “surface” composition of Sr2+, so it exhibits the best REDOX effect. The conclusion applied to three groups of samples. Although there was no significant difference in the REDOX performance of the three groups of samples, the formation temperature of La1−xSrxCoO3-δ could be decreased by using sucrose sol-gel method. Adding ethylene glycol in the preparation process of sucrose sol-gel method was unfavorable to the dry gelling process, but the time of gelling and dry gelling of S method was shorter than citric acid samples. Compared to citric acid samples, under the same calcination temperature and Sr content, the specific surface area of sucrose sample is larger. Therefore, on the basis of preparing samples with the same REDOX effect, sucrose sol-gel method without glycol can reduce the cost, simplify the process and improve the economic benefit.