Enhanced High-Frequency Properties of NiZn Ferrite Ceramic with Co_2Z-Hexaferrite Addition

摘要

Significantly enhanced dielectric and loss characteristics have been observed in Ni_(0.4)Zn_(0.6)Fe_2O_4 ferrite with various Ba_3Co_(2-) Fe_(24)O_(41) (Co_2Z) addition (x). Compared with pure NiZn and Co_2Z ferrites, the composite ceramics obtain much refined grains and notable high-frequency characteristics. With the introduction of Co_2Z into NiZn ferrite matrix, the resistivity is largely increased from the order of 10~6 Ω cm to the order of 10~8 Ω cm and the frequency stability of permittivity is dramatically enhanced. Co_2Z addition obviously improves the magnetic quality factor Q and reduces the dielectric loss of the ceramics at high frequency. For the samples with x = 20-30 wt%, permittivity ε' is almost unchanged from 1 MHz to 1 GHz, Q is greater than 10 in a wide frequency range, and dielectric loss tan δ_ε is observed to be of the order of 10~(-3) at 100 MHz, which is lower by two orders of magnitude compared with pure NiZn and Co_2Z ferrites. These characteristics are all desirable for magneto-dielectric ferrites in high-frequency applications.