Li Juan, Sun Xuetao
College of Materials Science and Engineering, Zhejiang University of Technology, Hangzhou 310014, China.
Research Center of Magnetic and Electronic Materials, Zhejiang University of Technology, Hangzhou 310014, China.
Materials (Basel). 2023 Aug 29;16(17):5897. doi: 10.3390/ma16175897.
La-Sr co-doped Ba(LaSr)CoFeO (x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0, respectively) hexaferrites were prepared by the solid-state method. W-type hexaferrite single phase structure with space group P63/mmc was obtained when the doping amount was x < 0.4 and an M-type hexaferrite and a spinel phase with smaller grains gradually replaced the W phase as the primary phases when x ≥ 0.6. The maximum Ms is 76.2 emu/g and the minimum Hc is 60 Oe at x = 0.4, as obtained by VSM analysis. The magnetoelectric properties of the samples were tested at 1-18 GHz with a vector network analyzer and the reflection loss was calculated based on transmission line theory. It was found that the introduction of an appropriate amount of La-Sr provides a large number of porosity defects while increasing the grain size, which can effectively improve the reflection of electromagnetic waves inside the material and dissipate more energy. At the same time, co-doping also makes the resonance frequency of the samples shift to lower frequency, resulting in tunable absorption properties in the C, X and Ku bands. When x = 0.2, the minimum reflection loss is -40.61 dB at 1.5 mm thickness, with the effective absorption bandwidth of 5.76 GHz in the X band; when x = 0.4, the minimum reflection loss is -37.45 dB at 2.5 mm, with the bandwidth of 4.97 GHz in the C band; when x = 0.6, the material has good absorption in both the X and Ku bands with the thickness less than 2 mm. The simple preparation method and good performance make La-Sr co-doped CoW ferrite a promising microwave absorbing material.
采用固态法制备了La-Sr共掺杂的Ba(LaSr)CoFeO（x分别为0.0、0.2、0.4、0.6、0.8和1.0）六铁氧体。当掺杂量x < 0.4时，获得了空间群为P63/mmc的W型六铁氧体单相结构；当x≥0.6时，M型六铁氧体和晶粒较小的尖晶石相逐渐取代W相成为主要相。通过振动样品磁强计（VSM）分析可知，当x = 0.4时，最大饱和磁化强度Ms为76.2 emu/g，最小矫顽力Hc为60 Oe。用矢量网络分析仪在1 - 18 GHz测试了样品的磁电性能，并根据传输线理论计算了反射损耗。结果发现，引入适量的La-Sr在增加晶粒尺寸的同时提供了大量的孔隙缺陷，这可以有效提高材料内部对电磁波的反射并耗散更多能量。同时，共掺杂还使样品的共振频率向低频移动，从而在C、X和Ku波段产生可调谐的吸收特性。当x = 0.2时，在厚度为1.5 mm时最小反射损耗为-40.61 dB，在X波段的有效吸收带宽为5.76 GHz；当x = 0.4时，在2.5 mm时最小反射损耗为-37.45 dB，在C波段的带宽为4.97 GHz；当x = 0.6时，该材料在厚度小于2 mm时在X和Ku波段均具有良好的吸收性能。简单的制备方法和良好的性能使La-Sr共掺杂的CoW铁氧体成为一种有前途的微波吸收材料。
