Modifying the hygroscopic property of La 2 O 3 by Pr, Sm and Nd doping

Combustion synthesized La2O3, La2-2xPr2xO3 (x = 0.025–0.30), La2-2xNd2xO3 (x = 0.025–0.50), La2-2xSm2xO3 (x = 0.025–0.30) and their subsequently formed hydroxide phases were characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The hydroxylation reaction (hygroscopic property) of oxides in an open atmosphere was monitored by X-ray diffraction (XRD). All of these oxides hydroxylate to form stable hydroxides at room temperature upon exposure to open atmosphere for certain interval of time. La2O3 shows rapid hydroxylation reaction as compared to other oxides (La2-2xM2xO3, M = Pr, Nd, Sm). It is observed that La2-2xPr2xO3 shows the slowest hydroxylation reaction compared to La2-2xNd2xO3 and La2-2xSm2xO3. Further, as the concentration of dopant ion concentration increases in each La2-2xPr2xO3 (x = 0.05, 0.15 and 0.30), La2-2xNd2xO3 (x = 0.05, 0.15, 0.30 and 0.50) and La2-2xSm2xO3 (x = 0.05, 0.15 and 0.30), the hydroxylation reaction becomes slower consecutively. Overall, 30% Pr doped La2O3 (La1.40Pr0.60O3) shows the highest stability (slowest rate of hydroxylation) in open atmosphere at room temperature.