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Qualitative Synthesis Lab Report

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(Co, Fe) doped (La, Ca) based chromites - (La0.8Ca0.2)(Cr0.9-xCo0.1Fex)O3
The transition metal doped perovskite compound, (La0.8Ca0.2) (Cr0.9-xCo0.1Fex) O3 (x=0.03, 0.06, 0.09, 0.12) was synthesized by mixing the powders of lanthanum oxide (La2O3, 99.99%), chromium oxide (Cr2O3, 99.99%), cobalt oxide (Co3O4, 99.99%), ferric oxide (Fe2O3, 99.99%) and calcium carbonate (CaCO¬3, 99.99%) in stoichiometric ratio according to the following equation.
0.4La2O3 + 0.2CaCO3 + ((0.9-x))/2Cr2O3 + 0.1/3Co3O4 + x/2Fe2O3 →
(La0.8Ca0.2)(Cr0.9-xCo0.1Fex)O3 +CO2 ↑ …… (1.2)
The appropriate quantities of starting materials were calculated by equation (1.2) and the molecular weights given in table 1.1. To synthesize (Co, Fe) doped (La, Ca) based chromites, …show more content…

Stoichiometric quantities of these powders were taken according to the following equation.

((1-x))/2 La2O3 + x CaCO3 + MnO2 → La1-xCaxMnO3 + CO2 ↑ …… (1.4)

Using the molecular weights of starting materials and by equation (1.4), the quantities of starting materials were calculated and given in table 1.5. These oxide powders were mixed and ground for 2 h using an agate mortar. These ground powders were then calcined in a tubular furnace at 1300 °C for 5 h for homogeneity. Then, the calcined powders were ground again using agate mortar for 3 h and further calcined at 1400 °C for 12 h. Thereafter, the powders were ground again by agate mortar for 3 h. These powders were then pelletized and the resultant pellets were further sintered at 1450°C for 15 h in a tubular furnace to get the required samples. The prepared …show more content…

Proper weight ratios of these oxide and carbonate powders were used according following equation.

( (1-x))/2 La2O3 + x SrCO3 + MnO2 → La1-xSrxMnO3 + CO2 ↑ …… (1.5)

The quantities of starting materials used are given in table 1.6. These weighed powders were mixed thoroughly and ground for 3 h using an agate mortar. Then, these ground powders were calcined at 1250 °C for 8 h. Then the calcined powders were ground again for 5 h using agate mortar and further sintered at 1400°C for 12 h. These sintered powders were ground once again for 3 h using agate mortar. The resultant powders were pressed into pellets and sintered at 1450 °C for 15 h. Then, the final sintered powders were ground again for further characterizations. The synthesized pellets of La1-xSrxMnO3, (x=0.3, 0.4 and 0.5) manganites are shown in figure

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