DEVELOPMENT OF NICKEL-ZINC FERRITE COMPOSITIONS WITH HIGH DIELECTRIC CONSTANT FOR RADIO-ABSORBING MATERIALS

The development of electronic and electrical equipment leaves a trace in the form of negative effects of unwanted electromagnetic radiation, from which protection in Ukraine is rare and is not actually regulated. In many countries, there are requirements for electromagnetic compatibility that apply to technical equipment that is exposed to and a source of electromagnetic interference. A growing number of technical devices, such as radios, radars, high-voltage power lines, and others, require effective protection against electromagnetic radiation. This is especially important in the context of the development of microelectronics and information technology, which are highly sensitive to such interference. In addition, unwanted electromagnetic radiation can be harmful to human health, contributing to the development of cancer. To protect against unwanted radiation, radio-absorbing materials are used, among which ferrite materials are effective. In particular, Ni-Zn ferrites show good results in absorbing radiation in the range from 50 MHz to 1 GHz. Nowadays, there is a growing demand for materials with high magnetic and dielectric constant to reduce the power of reflected radiation in the frequency range from 1 kHz to 50 MHz. An analysis of foreign scientific publications has shown that the dielectric constant of ferrites can be increased by increasing the barrier capacity due to an increase in the electrical resistance of grain boundaries. In this work, the influence of modifying additives and technological parameters of manufacturing nickel-zinc ferrite Ni0.3Zn0.7Fe2O4 for radio-absorbing materials was investigated. The optimal parameters of mixing and grinding of the material at the first and second stages have been established, which ensures the production of fired samples with a density close to the theoretical one. To explain the obtained properties of ferrites under the influence of modifying additives, the Okazaki model is presented, according to which the difference in the electrical conductivity of grains and the grain boundary layer in the high frequency region forms the barrier capacity. It has been experimentally established that an increase in the Fe2O3 content in the basic composition beyond the stoichiometry, as well as modification of the studied ferrite composition with calcium and titanium oxides, provides an increase in the dielectric constant, which contributes to the production of ferrites with a high absorption level in the frequency range up to 50 MHz.