| 摘要 |
Provided are Ni-Zn-Cu ferrite materials having high Q value and small absolute value of relative temperature coefficient of initial permeability(alphamuir) in a wide temperature range between -40deg.C and 160deg.C, and excellent stress-insensitive characteristic for inductors. The ferrite materials contain main constituents comprising 45.5-48mol% of Fe2O3, 5-10.5mol% of CuO, 26-30mol% of ZnO, and the balance of NiO, and additive, cobalt oxide within a range of 0.005-0.045wt.% in terms of CoO. In the ferrite sintered body, the mean grain size of the ferrite sintered body is desirably 5micrometer or less so that the absolute value of alphamuir-40~20 and the absolute value of alphamuir20~160 is less than 3 ppm/deg.C. Moreover, the sintered ferrites provide more than 140 of quality factor(Q value) at 125 kHz. It is to be noted that alphamuir-40~20 and alphamuir20~160 have the following definitions: alphamuir-40~20 = [(mui20 - mui-40)/mui-40^2] X [1/(T20 - T-40)]; alphamuir20-160 = [(mui160 - mui20)/mui20^2] X [1/(T160 - T20)], wherein mui-40, mui20, mui160 represent initial permeability at -40, 20 and 160 deg.C, respectively. The ferrite materials for inductors have more than 20 kgf/mm2 of bending strength, less than 5% of absolute value of a stress-insensitive characteristic, more than 300 of initial permeability(mui) at 125kHz. The stress-insensitive characteristic is a value obtained as follows: stress-insensitive characteristic=(L1-L0)/L0X100 (%), wherein L1 and L0 represent inductance values obtained when a uniaxial compressive force (1ton/cm2) is applied and a uniaxial compressive force (1ton/cm2) is not applied, respectively.
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