EVALUATION OF A Ni-Zn FERRITE FOR USE IN TEMPERATURE SENSORS

Abstract

Abstract-This work investigates the variation of the real part of the complex magnetic permeability of a Ni-Zn ferrite for application to temperature sensors. Ferrite samples were fabricated by means of the conventional ceramic method. Zinc, nickel and iron oxides were used as raw materials. The samples were sintered at 1200, 1300, and 1400 • C. The complex magnetic permeability of the samples was measured at temperatures ranging from −40 • C to +50 • C. The complex magnetic permeability of the samples was analyzed in the 100 kHz-100 MHz frequency range, and the temperature sensitivity of the magnetic permeability (∂µ r /∂T ) was analyzed at 100 kHz. The magnetic permeability variation of the ferrite permits to use it as a temperature transducer with a maximum temperature sensitivity of about −119 • C −1 . The highest magnitudes of temperature sensitivity occurred between +30 • C and +50 • C. Therefore, the ferrite could be sensitive enough to allow temperature measurements at the human body temperature level.The results indicate that the temperature range of maximum temperature sensitivity of the ferrite may be adjusted by means of appropriate selection of the fabrication parameters.

Electromagnetic characterization of Ni0.5Zn0.3Co0.2Fe2O4 bulk ceramics in the 1MHz-12GHz frequency range

“…The calculated lattice parameter was 8.379 Å and theoretical density calculated using Eq. 1 was ρ XRD = 5.34 g/cm 3 . Since the measured density of the pellet was ρ = 4.7 g/cm 3 , the densification of the sintered ferrite may be estimated as 88% TD.…”

“…1 was ρ XRD = 5.34 g/cm 3 . Since the measured density of the pellet was ρ = 4.7 g/cm 3 , the densification of the sintered ferrite may be estimated as 88% TD.…”

“…However, Mattei et al [46] reported M s of 305 kA/m for Ni 0.53 Zn 0.27 Co 0.2 Fe 1.98 O 4-δ , which is close to the saturation magnetization found in our sample. Since the density of our sample is 4.7 g/cm 3 , one can convert 71 Am 2 /kg into volume magnetization units, obtaining M s = 334 kA/m. The microstructure of the ferrite has a significant influence on its magnetization process because pores, grain boundaries and other types of discontinuities act as pinning sites to domain walls.…”

“…NiZn ferrites are spinel ferrimagnetic ceramics that have been extensively studied in the last decades and their electromagnetic properties have been characterized by several authors. They are particularly suitable for high frequency applications [1] and some examples of electronic devices in which NiZn ferrites are applicable are the following: sensors for current, gas, force/stress, and temperature [2][3][4][5][6], antennas [7] converters and inductors [8]. New research in the field of NiZn ferrites is still being developed, with interesting results in tunable magnetoelectric devices [9], non-volatile memory devices [10], low temperature solid oxide fuel cells [11], microwave-absorbing composites [12] and inductors for self-powered IoT devices [13].…”

“…The general formula of NiZn ferrites is Ni 1-x Zn x Fe 2 O 4 and the highest magnetic permeability in low frequencies (below 100 kHz) is expected when x = 0.7 [14]. However, the Curie temperature (T C ) of this composition is near the ambient temper- ature range [3] and this may be a problem in some applications. Cobalt substitution in NiZn ferrites increases T C [15] and consequently increases the temperature range of operation of the ferrite device, in spite of decreasing the magnetic permeability.…”