Investigation into La(Fe/Mn)O3 Perovskites Formation over Time during Molten Salt Synthesis

Molten salt synthesis (MSS) of complex oxides is generally investigated by characterization of the product phases with no insight into evolution of particlemorphology. In this work, LaFeO3and LaMnO3MSS was investigated in KF-KCl andLiCl-KCl at 850 degrees C using afeeding-and-samplingprocedure. By feeding the oxidereagents into a molten salt, the reaction starting point was clearly defined, whilesubsequent sampling of the melt provided means for tracking the phase compositionalong with the shape and size of product particles during MSS. Samples taken just after1 min contained perovskite particles along with reagents and intermediates, which wereconsumed over time to yield a pure product within 10-30 min. The shape and size ofperovskite particles sampled at different times during MSS were virtually unchanged, revealing a lack of notable growth. Theobserved fast MSS along with prevailing nucleation provided means to control perovskite particle size by varying the extent ofreagent dissolution. Thus, increasing the salt/reagent ratio (from 10:1 to 25:1) strikingly reduced the duration required to obtain apure product, along with decreasing the size of product particles (from 0.5-1.5 mu mto80-200 nm). Furthermore, performing MSSin KF-KCl, which exhibits greater oxide solubility compared to LiCl-KCl, resulted in a shorter duration and smaller perovskiteparticles (80-200 nm and 0.6-2.0 mu m, respectively). This insight into perovskite formation and growth during MSS and its kineticsprovides valuable guidelines for tuning MSS conditions to better control synthesis duration and particle size

Automated summary

The study investigates the synthesis of complex oxides in molten salt and finds that the duration and particle size of the product can be effectively controlled by adjusting the ratio of salt to reagent, providing valuable guidelines for tuning the synthesis conditions.