Power capacity enhancement and loss reduction induced by limited solid solubility of Ho3+ rare-earth substitution in NiCuZn spinel ferrites

Abstract

The application of NiCuZn ferrites (NCZFs) in high-power communication systems is constrained by their nonlinear excitation. To reduce nonlinear effects, it is essential for ferrite materials to possess a relatively high spin-wave linewidth (ΔHk). Doping with ions such as cobalt and rare-earth (RE) ions with fast relaxation has proven effective in increasing ΔHk of ferrites. However, the regulatory mechanism of doping NCZFs with RE ions with larger ionic radii remains unclear. In this study, Ho3+-substituted NCZFs were synthesized via a solid-state reaction route. The spatial distribution and substitution amount of the Ho3+ ions were carefully investigated via elemental and phase composition analysis, revealing the limited solid solubility of the Ho3+ ions in NCZFs. Some of the Ho3+ ions enter the lattice and occupy the octahedral sites, accelerating relaxation and increasing ΔHk to a maximum value of 2.63 kA·m−1. Insoluble Ho3+ ions combine with Fe3+ ions to form a HoFeO3 heterogeneous phase with Fe3+ ions at the grain boundaries, leading to iron deficiency within NCZF crystals and significantly reducing the dielectric loss tangent at microwave frequencies. These results reveal the great potential of Ho3+-substituted NCZFs for high-power, low-loss microwave applications.

Keywords

• nicuzn ferrites (nczfs)
• rare earth
• solid solubility
• spin-wave linewidth
• dielectric loss