Reaction mechanism of lanthanum nitrate-doped Mo–La material during solid–liquid spray doping processing

Abstract

At three critical temperatures which were obtained by thermo-gravimetry-differential thermal analysis–differential scanning calorimetry (TG/DTG/DSC) curves of lanthanum nitrate crystal, the air thermal decomposition experiments and solid–liquid spray doping simulation procedures of lanthanum nitrate crystal were carried out, and their products were analyzed by X-ray diffraction (XRD). Meanwhile, the spray doping processing of MoO2–50 wt% La(NO3)3 composite powder was undergone with lanthanum nitrate solution as the dopant, and doped MoO2 powder was analyzed by XRD. The results demonstrate that during the traditional solid–liquid spray doping processing, lanthanum nitrate, in the form of either crystal or aqueous solution, would be converted into La(NO3)3·4H2O by the dehydration reaction, rather than be decomposed to La2O3 and NO or NO2. Therefore, it is inferred that the oxynitride gas produced from the process is attributed to the decomposition of residual HNO3 in lanthanum nitrate crystal. The source of HNO3 is supported by the chemical composition of lanthanum nitrate crystal.