Solid-phase synthesis of high-entropy crystals with the M-type hexaferrite structure in the Ba(Fe,Mn,Zr,Ga,Al)12O19, Ba(Fe,Sn,Zn,Ga,Al)12O19 and (Ba,Sr)(Fe,Ga,In,Al)12O19/B2O3 systems

Experiments to obtain new high-entropy oxide phases with the M-type hexaferrite structure, the composition of which reflects the MeR12O19 formula, were carried out. In this formula, the Me components are Ba, Sr, and in the role of the R components, along with the previously used - Fe, Mn, Al, Ga, In - a number of new components unused previously for these tasks: Zr, Sn, Zn. Taking into account the data presented in the literature, at this stage of the research the studies with samples belonging to three compositions were carried out: Ba(Fe,Mn,Zr,Ga,Al)12O19, Ba(Fe,Sn,Zn,Ga,Al)12O19, and (Ba,Sr)(Fe,Ga,In,Al)12O19/B2O3. In the first case, it was planned to establish whether zirconium can act as a component of the high-entropy phase with the M-type hexaferrite structure. The second composition made it possible to establish whether tin and zinc could be used together as such components (it was assumed that the combination of the tetravalent tin and bivalent zinc would make it possible to achieve mutual compensation of the charges of the ions of these metals, obtaining an average value of +3). While studying the third composition, it was planned to study the possibility of using additions of low-melting components (boron oxide and salts formed by boron oxide and alkaline earth elements) in the process of the formation of crystals of the high-entropy phase. The study of the structure and chemical composition of samples of the Ba(Fe,Mn,Zr,Ga,Al)12O19, Ba(Fe,Sn,Zn,Ga,Al)12O19, and (Ba,Sr)(Fe,Ga,In,Al)12O19/B2O3 systems, obtained by solid-phase synthesis, showed the possibility of formation of high-entropy microcrystals with the M-type hexaferrite structure at all temperatures used. In the course of the work carried out, it was found that in the composition of the high-entropy MeR12O19 phase, a number of new components, unused previously for these tasks, can be used as the R components: Zr, Sn, Zn. The use of a low-melting additive in the composition of the mixture based on boron oxide did not lead to a noticeable improvement in the results of crystal growth (and, in addition, the sample naturally turned out to be contaminated by boron compounds). The XRD results demonstrate that an increase in the synthesis temperature (in our case, up to 1400 °C) has a positive effect on its results. All these facts should be taken into account in the course of subsequent experiments to create single-phase samples suitable for studying their characteristics.