Effects of Co2O3 concentration on high Q-factor NiCuZn ferrites for 13.56 MHz radio identification communication

Co2O3-doped NiCuZn ferrites with a high (group A) or low (group B) permeability were prepared using the conventional ceramic method to obtain high Q-factor NiCuZn ferrites for a 13.56 MHz near-field-communication (NFC) system. The XRD patterns of samples from both groups exhibited single spinel phase. Permeability monotonously decreased with increasing Co2O3 content, whereas sintering density and saturation magnetic flux density (Bs) slightly changed with Co2O3 content. The permeability of 0.45 wt% Co2O3-doped ferrite (A0.45) was similar to that of 0.10 wt% Co2O3-doped ferrite (B0.10). However, the former sample presented a considerably higher Q-factor than the latter sample. The former sample also presented enhanced stability variation of Q-factor with frequency, which indicated an improved electromagnetic shielding function for the NFC system. The mechanisms involved were also elucidated.