Processing and characterization of a Ni-Co ferrite for sensor applications

Abstract

Ni-Co ferrites are magnetostrictive ceramics that have potential application in magnetostrictive/ magnetoelastic sensors, as well as in magnetoelectric composites. Ni-rich Ni-Co spinel ferrite samples were processed by the ceramic method and bulk samples were sintered at 1350 ºC in the solid state and at 950 ºC with Bi2O3 liquid phase. The sintered samples were characterized by light microscopy, scanning electron microscopy, Raman spectroscopy, vibrating sample magnetometry and capacitance dilatometry. With Bi2O3 additions as small as 0.6 mol% it was possible to sinter the Ni-Co ferrite at 950 ºC, obtaining high-density samples; however, such liquid-phase sintered samples presented iron oxide particles. The studied samples presented magnetoelastic sensitivities very close to CoFe2O4, with significantly lower magnetic hysteresis. The results thus indicate that the magnetic properties of the samples analyzed are suitable for applications in magnetomechanical sensors.

Microstructural characterization of ceramic artifacts made using the raku technique

“…In addition, quartz brings solidity to the ceramic during the firing process, attenuating the linear shrinkage and functioning as a skeleton, but increasing the porosity level. (Brito, Cunha, Machado, Silva, & Nunes, 2015;Castro, Soares, Nascimento, & Bison, 2015;Zanelli et al, 2019).…”

“…After the second firing, the uncoated specimens showed higher linear shrinkage, 5.39% on average and with standard deviation of 0.99%, while the coated specimens presented linear shrinkage of 4.82% and default of 0.69%. The gradual increase in linear shrinkage is related to the higher degree of sintering and densification, which results in physical changes and decreased specimen volume (Abubakar, Muthuraja, & Ahmad, 2020;Tsega, 2017;Brito et al, 2015;Rodrigues et al, 2014;Dal Bó, Melchiades, Bosch, & Hotza, 2012;Luiz Fernando Teixeira Queiroz, 2009;Santos, Melchiades, & Boschi, 2007;Galesi, Lepri Neto, Melchiades, & Ortega Boschi, 2005;Tozi, 1992;Pérez, 1991;Parmelle, 1973).…”

Mechanical, Magnetic, and Microstructural Characterization of Ni0.9Co0.1Fe2O4 Produced by the Ceramic Method

“…Among ferrites, the cobaltbased retains the highest magnetostriction levels, which makes them promising candidates for applications in magnetomechanical and magnetoelectric sensors 5,6 . Ni-based ferrites also have interesting magnetostrictive properties for sensors applications 7,8 . However, for some applications in magnetomechanical sensors, the material must have adequate mechanical strength, which requires strict control of the microstructure.…”

“…In a certain Co fraction, the absolute anisotropy will thus reach a minimum, yielding a maximum in magnetic permeability 11 . 7,[12][13][14][15][16] . It is possible to observe a large dispersion of M s values of Ni-Co ferrites with the same composition, but produced by different routes.…”

“…The saturation magnetostriction parallel to the field was -36ppm, which is higher than the value reported in 28 for a cobalt-free Ni ferrite (λ s = -26ppm for NiFe 2 O 4 ) and very close to our previous result of -35ppm reported in ref. 7 for an Al-free Ni-Co ferrite with similar composition. The magnitude of the saturation magnetostriction value of the NiCo ferrite is within the range from magnetostrictive Also, the magnetic field at which the maximum sensitivity occurs indicates the point of optimum performance of the material 30,31 .…”