Structural, magnetic and microwave electromagnetic properties in La-substituted quaternary ferrite

Enhanced Microwave Absorption Performance in Sr-Modified La2NiO4±δ Nickelate With High Dielectric Loss

“…The obtained xerogel was ground, pre-sintered to burn out organics, and sintered at 1000 • C for 4 h. Subsequently, the sintered powder was water-milled, dried, and granulated by sieving. A similar experimental procedure can be seen in previous reports (Liu et al, 2019). Prior to heating, the milled powders were mixed with 2% polyvinyl alcohol, pressed into pellets, and placed in a platinum crucible.…”

“…As clearly seen, the optimal absorption peak downshifts to low frequency from 12.7 to 9.1 GHz when the absorption layer gets thicker. Such peak shifting can be reasonably described by the quarter-wave matching model (Liu et al, 2019), where t calm and f r are the matching thickness and frequency of minimum RL peaks and c represents the velocity of light in vacuum. The calculated thickness t calm shown in Figure 6A agrees well with the matching thickness t matm .…”

“…Complex permeability and permittivity (ε r = ε' -jε and µ r = µ -jµ ) were assessed on a vector Network Analyzer (Agilent N5230A) in a frequency range of 8-18 GHz. The RL of composites was collectively calculated based on the transmission line theory from the measured complex permeability and complex permittivity (He et al, 2018;Liu et al, 2019).…”

“…Further, the larger tanδ e than tanδ m indicates that the main contribution of the attenuation capability comes from the high dielectric loss. The attenuation ability can also be evaluated by the attenuation constant γ, given as (Fang et al, 2016;Liu et al, 2019):…”

“…Directed at this, broadband and high-efficiency microwave absorbing materials (MAMs) are urgently demanded to weaken or eliminate the unwanted electromagnetic signals for next-generation military electronics in aspects of all-electric aircraft, stealth fighter, defense security, etc. (Qi et al, 2016;Wei et al, 2018;Liu et al, 2019). Designing high-performance MAMs and applying these functionalized materials in actual operation are scientifically interesting and of technological importance.…”