Study of the Thermal Stability in Air of LaNi5 by DSC, EDX, TEM and XRD Combined Techniques

In this work, the thermal stability in air of LaNi5 and its reaction products were analyzed. The structural and microstructural parameters were determined by X-ray diffraction and TEM techniques. According to the results of XRD/TEM, the starting material is monophasic with hexagonal structure (P6/mmm, a = 5.019 (0) Å, c = 3.982 (7) Å). Thermal measurements were made by differential scanning calorimetry, using heating rates between 1 and 25 °C.min-1. The calorimetric curve corresponding to a heating rate of 1 °C.min-1 shows stability of the intermetallic up to (140 ± 1) °C. The thermal decomposition evolves as three successive exothermic global events. According to the measured curve, the maximum peaks are produced at (205 ± 1) °C, (258 ± 1) °C and (391 ± 1) °C, respectively. Thermal evolution lead to the formation at 600 °C of the final products La2O3 (P-3m1, a = 3.945(0) Å; c = 6.151(0) Å), NiO (Fm3m, a = 4.178(0) Å) and LaNiO3 (R-3c, a = 5.457(3) Å; and c = 13.146(2) Å). The elemental composition was analyzed by EDS.