Phase Formation, Microstructure and Permeability of Fe-Deficient Ni-Cu-Zn Ferrites, (I): Effect of Sintering Temperature
Phase Formation, Microstructure and Permeability of Fe-Deficient Ni-Cu-Zn Ferrites, (I): Effect of Sintering Temperature
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DOI：
10.3390/magnetochemistry7080118
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发表时间：
2021-08
期刊：
影响因子：
2.7
通讯作者：
C. Priese;J. Töpfer
中科院分区：
文献类型：
--
作者：
C. Priese;J. Töpfer
我们研究了化学计量和缺铁Ni-Cu-Zn铁氧体的致密化、相形成、显微结构和磁导率，其成分为Ni0.30Cu0.20Zn0.50 + zFe 2-zO 4-（z/2），其中0 ≤ z ≤ 0.06，在900 °C至1150 °C的温度下烧结。收缩率从z = 0的1000 °C向较低温度移动，并且在z = 0.02的900 °C时达到其最大速率。当烧结温度Ts ≤ 1100 °C时，化学计量比的铁氧体表现出单相铁氧体晶粒的规则生长。在1150 °C下烧结导致少量Cu 2 O的形成，从而引发过度的晶粒生长。在900-1000 °C下烧结后，缺Fe组合物（z > 0）形成与少数CuO相共存的贫Cu化学计量铁氧体。在Ts ≥ 1050 °C时，CuO转变为Cu 2 O，并且观察到夸大的晶粒生长。利用XRD、SEM和EDX研究了Cu氧化物第二相的形成。铁氧体的磁导率随着烧结温度的升高而增加，在Ts = 1000 °C时，z = 0时的最大磁导率为μ = 230，z = 0.02时的最大磁导率为μ = 580。在较高的烧结温度下，磁导率降低，这是由于在大晶粒中形成具有晶内孔隙率的微观结构和非磁性Cu氧化物晶界相。
We have studied the densification, phase formation, microstructure, and permeability of stoichiometric and Fe-deficient Ni-Cu-Zn ferrites of composition Ni0.30Cu0.20Zn0.50+zFe2-zO4-(z/2) with 0 ≤ z ≤ 0.06 sintered at temperatures from 900 °C to 1150 °C. The shrinkage is shifted from 1000 °C for z = 0 towards lower temperatures and reaches its maximum rate at 900 °C for z = 0.02. Stoichiometric ferrites show regular growth of single-phase ferrite grains if sintered at Ts ≤ 1100 °C. Sintering at 1150 °C leads to the formation of a small amount of Cu2O, triggering exaggerated grain growth. Fe-deficient compositions (z > 0) form Cu-poor stoichiometric ferrites coexisting with a minority CuO phase after sintering at 900–1000 °C. At Ts ≥ 1050 °C, CuO transforms into Cu2O, and exaggerated grain growth is observed. The formation of Cu oxide second phases is investigated using XRD, SEM, and EDX. The permeability of the ferrites increases with sintering temperature up to a maximum permeability of µ = 230 for z = 0 or µ = 580 for z = 0.02, respectively, at Ts = 1000 °C. At higher sintering temperatures, the permeability decreases, which is due to the formation of a microstructure with intra-crystalline porosity in large grains, and a non-magnetic Cu oxide grain boundary phase.