Oxygen magnetic materials, control

Magnetic materials—control of oxygen composition and physical properties of Mn-Zn ferrites... 

Oxides play many roles in modem electronic technology from insulators which can be used as capacitors, such as the perovskite BaTiOs, to the superconductors, of which the prototype was also a perovskite, Lao.sSro CutT A, where the value of x is a function of the temperature cycle and oxygen pressure which were used in the preparation of the material. Clearly the chemical difference between these two materials is that the capacitor production does not require oxygen partial pressure control as is the case in the superconductor. Intermediate between these extremes of electrical conduction are many semiconducting materials which are used as magnetic ferrites or fuel cell electrodes. The electrical properties of the semiconductors depend on the presence of transition metal ions which can be in two valence states, and the conduction mechanism involves the transfer of electrons or positive holes from one ion to another of the same species. The production problem associated with this behaviour arises from the fact that the relative concentration of each valence state depends on both the temperature and the oxygen partial pressure of the atmosphere. 

Several methods have been used to produce different types of OL-1, OMS-1, and OMS-2 materials. The materials that are produced by various methods lead to vastly different materials, that have unique chemical and physical properties. Some of the properties that can be controlled are particle size, color, morphology, average manganese oxidation state, thermal stability, ion-exchange capacity, electrical conductivity, magnetic properties, crystallinity, defect density, desorption of oxygen, and catalytic properties. Table IV summarizes 16 different classes of OMS-1, OMS-2, OL-1, and amorphous manganese oxide (AMO) materials that we have prepared. These materials are separated into different classes because they show different crystalline, chemical and physical properties. For the case of OMS-1 these materials... 

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