A Fast, Low-Temperature Synthesis Method for Hexagonal YMnO₃ : Kinetics, Purity, Size and Shape as Studied by In Situ...

The reaction mechanisms, phase development and kinetics of the hydrothermal synthesis of hexagonal-YMnO₃ from Y₂ O₃ and Mn₂ O₃ using in situ X-ray diffraction are reported under different reaction conditions with temperatures ranging from 300 to 350 °C, and using 1, 5 and 10 m KOH, and 5 m NaOH mineraliser. Reactions initiated with Y₂ O₃ hydrating to Y(OH)₃ , which then dehydrated to YO(OH). Higher temperatures and KOH concentrations led to faster, more complete dehydrations. However, 1 m KOH led to YO(OH) forming concurrently with Y(OH)₃ before Y(OH)₃ fully dehydrated but yielded a very low phase purity of hexagonal-YMnO₃ . Using NaOH mineraliser, no YO(OH) was observed. Dehydration also initiated at a higher temperature in the absence of Mn₂ O₃ . The evolution of Rietveld refined scale factors was used to determine kinetic information and approximate activation energies for the reaction. The described hydrothermal synthesis offers a fast, low-temperature method for producing anisometric h-YMnO₃ particles.