Preparation of high-entropy layered double hydroxides with a hydrotalcite structure

High-entropy hexacationic layered double hydroxides of the cationic composition MgNiCoAlFeY were obtained by five different methods: coprecipitation at constant pH, coprecipitation at constant or variable pH followed by hydrothermal treatment, microwave assisted solvothermal, hydrothermal, mechanochemical method followed by hydrothermal treatment. All samples, except for the one obtained by coprecipitation at variable pH, are phase pure, with a uniform distribution of cations. The samples were characterized by X-ray diffraction, infrared spectroscopy, Raman spectroscopy, transmission electron microscopy. Thermal transformations of the samples were studied. The synthesis method affects the characteristics of the samples. The sample obtained by hydrothermal synthesis at variable pH possesses magnetic properties. The largest particles and those morphologically close to the hexagonal shape are formed by coprecipitation followed by hydrothermal treatment. The sample obtained by the microwave assisted solvothermal method is characterized by lower thermal stability.