	US 7,476,482 B2
	Mg-based ferrite, an electrophotographic development carrier containing the ferrite, and developer containing the carrier
Hidehiko Iinuma, Shibukawa (Japan); Masatomo Hayashi, Shibukawa (Japan); Natsuki Matsuura, Shibukawa (Japan); and Yukinari Oguma, Shibukawa (Japan)
Assigned to Kanto Denka Kogyo Co., Ltd., Tokyo (Japan)
Appl. No. 10/578,901 PCT Filed Nov. 05, 2004, PCT No. PCT/JP2004/016811 § 371(c)(1), (2), (4) Date May 12, 2006, PCT Pub. No. WO2005/048276, PCT Pub. Date May 26, 2005.
Claims priority of application No. 2003-382668 (JP), filed on Nov. 12, 2003; and application No. 2004-264875 (JP), filed on Sep. 13, 2004.
Prior Publication US 2007/0087282 A1, Apr. 19, 2007
Int. Cl. G03G 9/107 (2006.01); C04B 35/40 (2006.01); H01F 1/00 (2006.01)

U.S. Cl. 430—111.31 [252/62.63; 252/62.64]

16 Claims

1. An Mg-based ferrite material consisting essentially of X₂O_n, MgO and Fe₂O₃components or of X₂O_n, CaO, MgO and Fe₂O₃components, and having a composition of formula (1):

X_aMg_bFe_cCa_dO_e (1)

wherein

X is Li, Na, K, Rb, Cs, Sr, Ba, Y, La, Ti, Zr, Hf, V, Nb, Ta, Al, Ga, Si, Ge, P, Sb, Bi or a combination thereof; and

a, b, c and d satisfy

0.001≤R(X)≤0.15

wherein

R(X) is represented by the formula:

R(X)=a×(Aw(X)+(n/2)×Aw(O))/(a×(Aw(X)+(n/2)×Aw(O))+b×Fw(MgO)+(c/2)×Fw(Fe₂O₃)+d×Fw(CaO));

Aw(X) and Aw(O) are an atomic weight of X and an atomic weight of O, respectively;

n is an oxidation number of X; and

Fw(A) is a formula weight of A,

0.01≤b/(b+c/2)≤0.85 and

0≤R(Ca)≤0.15

wherein

R(Ca) is represented by the formula:

R(Ca)=d×Fw(CaO)/(a×(Aw(X)+(n/2)×Aw(O))+b×Fw(MgO)+(c/2)×Fw(Fe₂O₃)+d×Fw(CaO));

wherein

Fw(A) is the same as defined in R(X),

e is determined by the oxidation numbers of X, Mg, Fe and Ca;

wherein the Mg-based ferrite material has a dielectric breakdown voltage in the range of 1.5-5.0 kV; and

wherein the Mg-based ferrite material has a saturation magnetization in the range of 30-80 emu/g measured at 14 kOe using a vibrating sample magnetometer.