Experimental:
The following materials were used as precursors for synthesis of perovskite particles. Lanthanum Nitrate (La(NO3)3-6H2O) and Cobalt Nitrate (Co(NO3)2-6H2O) as a supplier of metal elements, glycine (C2H5NO2) and urea (CH4N2O) as fuel, and PVP as a surfactant were used in these experiments. All of the precursor materials were purchased from Merck-Germany and used in the experiments without further purification.
Firstly, 0.1M solutions of lanthanum nitrate and cobalt nitrate was prepared in 100 ml of distilled water in a 250 ml beaker and stirred on a magnetic stirrer for 15 minutes until the material was completely dissolved and a uniform pink solution was obtained. In the second step, four different samples were prepared, as shown in Table 1. The stoichiometric amount of glycine and urea were added slowly to the solution. The glycine/metal and urea/ metal ratio were kept 1 and 2 in this experiment (F/O=1 & 2). The solution temperature was increased to 60 °C and PVP by 5% by weight of the available metals was added. PVP played the role of surfactant in the experiment, to help obtain a uniform shape and narrow size distribution. Solutions were mixed using vigorous stirring on a magnetic stirrer for half an hour. The next step was combustion. At this stage, the solution temperature was increased up to 90 °C in order to evaporate water slowly, followed by gelation and combustion. The solution was stirred using a magnetic stirrer, until combustion occurred.
The powder was washed with distilled water and centrifuged at 2000 RPM for 15 minutes for three times, and collected nanoparticles were calcined at 600 °C for 2 hours in a furnace.
Table 1: experimental conditions.