Synthesis of La_(1-x)Sr_xCoO_(3-δ) by a Polymeric Precursor Route using Microwave Heating

摘要

La_(1-x)Sr_xCoO_(3-δ)(x=0, 0.2, 0.5) powders were prepared by a polymeric precursor route, with the application of microwave heating for the precursor preparation. Single-phase oxide powders are obtained after calcination at 700°C for x=0, 0.2 and 1300 °C for x=0.5. XRD, FTIR and TG-DTG measurements were used to examine the powder precursors as well as the intermediate and final products. SEM images indicated the small grain size of samples with x=0, 0.2. Conductivity and thermal expansion were measured by means of DC method and dilatometry respectively. The end member LaCoO_(3-δ) showed a semiconducting behaviour, while doped samples showed a metallic behaviour at high temperatures. La_(0.8)Sr_(0.2)CoO_(3-δ) showed the highest conductivity of all samples investigated, at temperatures higher than 300 °C.