The Synthesis and Characterization of M-type and Y-type Hexaferrites

Abstract

Hexagonal ferrites doped with metal oxides have long been used in a variety of fields such as in sensors, actuators and other hardware. They are inherently stable and exhibit different properties, such as the magnetoelectric effect, which can be tuned through choice of structure and dopants.

The production of magnetoelectric hexaferrites can be costly and complicated. In this thesis a method based on the solid-state route is implemented and the resulting sample investigated and characterized. Furthermore, the viability of using metal carbonates instead of metal oxides was investigated alongside.

The end goal was to synthesize the Y-type BSMFO, using carbonates of barium, strontium and magnesium. To achieve this, the synthesis method was first applied in production of M-types doped with barium and strontium, as well as Y-types doped with different doping amounts of barium, strontium and magnesium carbonates.

The method applied was based on manual grinding of components and sintering at 1200 degrees for 24 hours with a heating rate of 180 degrees. The resulting sample was re-ground and an X-ray diffraction characterization performed. This was followed by Rietveld refinement using the software FullProf and compared to previously published crystallographic data.

Through this simple process, it was found that simple Sr and Ba M-types could be synthesized to an extent, but the method needs modification to synthesize significant samples of the sought after Y-types. Unfortunately the Y-type BSMFO was not able to be synthesized, but insights into further development of the method was found such as investigating how changes in the sintering process affects the end result.

Popular Abstract

Materials can be classified by components, structure, uses and other important properties. To construct each material one needs to be cautious when choosing components and synthesis method. To evaluate the result of the tried method, one needs to characterize it using a method that gives a certain fingerprint, which can then be compared to previous studies and either confirm whether or not the method results in the sought after product being formed.

Iron is an earth metal with strong magnetic properties. It has been used in electromagnetic devices and appliances for more than 100 years, from delicate sensors to kitchen magnets. However, iron oxides easily and turns into an iron oxide (rust). Although the added oxygen atoms changes it's properties, it is still an iron rich, easily accessible and easily manageable compound. An iron oxide, also called a ferrite, is also a really good building block for more complex structures. Hexaferrites are, in turn, iron oxides with a hexagonal crystal structure and can be described as a stacking of distinct layers.

Hexaferrites can be built onto with other metal atoms, which are called dopants. These atoms are usually added by milling together the iron oxide with other metal oxides, then in some way making these finely milled powders react by adding energy. In our case, we chose to use metal carbonates (similar to regular chalk) with the metal component being either Barium, Strontium or Magnesium, instead of metal oxides in the mix. This was followed by a process similar to baking, called sintering, the mix in an oven at 1200 degrees for 24 h in order for the right reaction to occur. To make sure that the different powders did react, the sample was then reground and sintered again. The goal for this thesis was to test this method by producing two different sorts of hexaferrites: M-types and Y-types. These two types are different in what kind of smaller blocks that the molecules are built from, with Y-types being a more complicated structure.

The crystal structure that the hexaferrite are made up of can be described in detail from different geometric parameters. These can in turn be determined from an X-ray diffraction experiment. In a typical X-ray diffraction, a laser will scan a thin sample and the different atomic layers will diffract the light in different angles. This gives rise to a pattern unique for each different structure and atomic composure, which can be analysed with different softwares and methods. We chose the typical method of Rietveld refinement, in which the differences in produced and expected "patterns" are compared and the difference is characterized through a fitting parameter called χ^2.

The result from our more simple method of creating a hexaferrite was ambivalent. For the simpler and smaller M-type structure, both hexaferrites doped with barium and strontium can be concluded to have been produced. However, the more complex Y-types which combinations of barium, strontium and magnesium, could not be concluded to have been produced. Although, the diffraction pattern produced was similar to that produced in other studies, some of the sought after structure could have been produced but not in pure form. It is suspected that different, smaller and more stable molecules could have been produced during the sintering process and remained in the sample. This would disturb the diffraction pattern produced through the X-ray diffraction experiment. It could also be suspected that the metal carbonates used might not be a simple replacement for the metal oxides and might require further changes in the method.

It can be concluded that the applied simple synthesis method has potential. However, since it is suspected that different unwanted products were produced alongside the wanted structure while sintering, it needs to be modified. This can be done by investigating other sintering temperatures and sintering times.

• author: Ahlqvist Moberg, Elvira
• supervisor: Elizabeth Blackburn; Oskar Stepancic
• organization: Department of Physics; Synchrotron Radiation Research
• course: FYSK04 20241
• year: 2026
• type: M2 - Bachelor Degree
• subject: Physics and Astronomy
• language: English
• id: 9218104
• date added to LUP: 2026-02-25 11:03:11
• date last changed: 2026-02-25 11:03:11