Based On The Preparation Of The Sol - Gel Method Strontium Lanthanum Powder And Around The Knot,

Nano-La_1-xSr_xCrO₃ was prepared by sol-gel process and was compacted into green bodies under high pressure. Then the green bodies were produced by pressureless sintering process in air. The physical properties of sinters were measured.The phase transformation from dry-gel to crystal was investigated by means of TG, DSC and XRD. The experimental results show that chromite phase, such as La_0.9Sr_0.1CrO₃, formed continuously during crystallization process, which is mainly composed of four steps: 1) carbonates first formed by decomposing metal citrates; 2) the decomposition of carbonates occurred metal oxides; 3) La_0.9Sr_0.1CrO₄ were synthesized by the reaction of metal oxides; 4) chromite phase formed lastly due to the decomposition of chromate phase. La_0.9Sr_0.1CrO₃ can be obtained by being calcined over 700°C for 2 hours. XRD results of powders show that (La,Sr)CrO₃ and SrCrO₄ coexist when x>0 and there is just orthorhombic (La,Sr)CrO₃ with x=0 or 0.1. HREM images display that when calcined at 800°C, the powders of Sr-doped lanthanum chromite are small size, uniform and dispersive.The sintering process of La_1-xSr_xCrO₃ nanopowders shows that the content of Sr-doped, binder content (polyvinyl alcohol/PVA), calcination time and sintering temperature have great effect on the sintering properties of Sr-doped lanthanum chromites. Result demonstrates that the samples with x<0.3 took on single phase, while in the case of x>0.3, traces of a second phase (SrCrO₄) were observed. The linear shrinkage of samples increases with the content of Sr-doped. The influnce of calcination time on sintered samples is the longer calcination time used, the less of the pore amount. Linear shrinkage increases with the sintering temperatures enhancing but is hardly affected by calcination time.Electrical properties of sintering pellets were characterized by four points resistivity test system. The result demonstrates that the electrical resistivity decreases with calcinations time increasing. Further study shows the electrical resistivity decreases with x increasing for x<0.2 and the value does not vary greatly for x>0.4.