High-frequency MnZn soft magnetic ferrite by engineering grain boundaries with multiple-ion doping

Synergistic effect of V2O5 and Bi2O3 on the grain boundary structure of high-frequency NiCuZn ferrite ceramics

“…Now that all the samples possess a small grain size of approximately 1 μm, the variation in P e can be ascribed to the fluctuating electrical resistivity. The continuous distribution of [15,18,51]. P r originating from the domain wall resonance is usually considered to be the dominant P cv [10].…”

“…Other typical examples include CaO, SiO 2 , and Co 2 O 3 , with the doping of the first two oxides, leading to the improvement of resistivity and eddy-current loss by forming a high resistive amorphous phase in the grain boundary [37,38] and doping of the last oxide, improving the frequency and temperature dependence of ferrites due to its large magnetocrystalline anisotropy [39,40]. Through numerous trial-and-error experiments based on the above perception, the operating frequency of ferrite has been elevated to 3-5 MHz [15,38,41,42], and passable performances of WBG-based power electronics have been obtained phenomenologically [4,5]. However, previous studies have concentrated more on grain size modifications and improvements of intrinsic magnetic properties, and the underlying synergistic mechanism of multiple-ion doping and the evolution of grain boundaries are seldom discussed, which are the basis for exploiting high-performance soft magnetic ferrites in the long term.…”

“…The high intrinsic resistivity minimizes high-frequency eddy-current loss, making soft magnetic ferrite the www.springer.com/journal/40145 most promising candidate for high-frequency applications [13,14]. The residual loss that originates from magnetic domain-wall resonance is bound up with microstructure, especially grain size, since the domain structure in a single crystalline grain could transform from a multidomain regime to a monodomain regime with a reduced grain size [15][16][17]. Meanwhile, further suppression of eddy-current loss could be achieved by refining the grain structure [18,19].…”

Atomic-scale observation of calcium occupation in spinel cobalt ferrite towards the regulation of intrinsic magnetic properties

“…Spinel structured ferrites (MFe 2 O 4 , M = Fe, Co, Ni, Mg…) refer to magnetic oxides that have the same crystal structure as the naturally formed MgAl 2 O 4 mineral. 1 They are widely applied in power electronics (transformers, inductors), [2][3][4] sensors, 5 catalysis, 6 magnetic imaging, 7 etc. due to their adjustable magnetic and physical properties.…”

“…For a given MFe 2 O 4 spinel ferrite, its magnetic properties can be effectively tailored by extra elemental doping. 3,13,[18][19][20][21][22] Traditionally, there are three types of dopant mechanisms including (i) soluble cations (Ti 4+ , 23 Sn 4+ , 24 etc.) that may incorporate into the tetrahedral or octahedral sites of the spinel lattice, modifying the intrinsic properties such as magnetization, anisotropy and resistivity; (ii) dopants (SiO 2 , 25 CaO, 26 ZrO 2 27 and HfO 2 28 ) that tend to precipitate at the grain boundaries, prohibiting grain growth and acting as the highly resistive grain boundary phase; (iii) oxides with a low melting point (V 2 O 5 , 29 Bi 2 O 3 30 and MoO 3 31 ) that form a liquid phase during the sintering of bulk ferrites.…”