A ceramic composition contains Fe, Cu, Ni, Zn, Co, and Cr. When Fe, Cu, Ni, and Zn are converted to Fe.sub.2O.sub.3, CuO, NiO, and ZnO, respectively, and a total amount of Fe.sub.2O.sub.3, CuO, NiO, and ZnO is 100 parts by mole, the ceramic composition contains from 48.20 to 49.85 parts by mole Fe in terms of Fe.sub.2O.sub.3, from 2.00 parts to 8.00 parts by mole Cu in terms of CuO, from 11.90 to 18.70 parts by mole Ni in terms of NiO, and from 27.00 to 33.50 parts by mole Zn in terms of ZnO. When Fe, Cu, Ni, and Zn are converted to Fe.sub.2O.sub.3, CuO, NiO, and ZnO, respectively, and a total amount of Fe.sub.2O.sub.3, CuO, NiO, and ZnO is 100 parts by weight, the ceramic composition contains from 5 to 100 ppm Co in terms of CoO and from 10 to 400 ppm in terms of Cr.sub.2O.sub.3.

In an aspect, a ferrite composition comprises a Ru—Co.sub.2Z ferrite having the formula: (Ba.sub.3-xM.sub.x)Co.sub.2(M′Ru).sub.yFe.sub.24-2y-zO.sub.41, wherein M is at least one of Sr, Pb, or Ca; M′ is at least one of Co, Zn, Mg, or Cu; x is 1 to 3; y is greater than 0 to 2; and z is −4 to 4. In another aspect, an article comprises the ferrite composition. In yet another aspect, method of making the ferrite composition comprises mixing ferrite precursor compounds comprising Fe, Ba, Co, and Ru; and sintering the ferrite precursor compounds in an oxygen atmosphere to form the Ru—Co.sub.2Z ferrite.

The present invention relates to a ferrite particle containing a crystal phase component containing a perovskite crystal represented by a compositional formula: RZrO.sub.3 (provided that R represents an alkaline earth metal element), having a surface roughness Rz of 0.8 .Math.m or more and 3.5 .Math.m or less, and having a standard deviation Rzσ of the surface roughness Rz falling in a range represented by the following formula 0.15 × Rz ≤ Rzσ ≤ 0.60 × Rz. The ferrite particle can be used as an electrophotographic developer carrier core material. In addition, an electrophotographic developer carrier and an electrophotographic developer can be obtained.

The present invention relates to a ferrite particle, containing a crystal phase component containing a perovskite crystal represented by the compositional formula:

RZrO.sub.3 (provided that R represents an alkaline earth metal element), and having an apparent density in a range represented by the following formula:

1.90≤Y≤2.45

provided that Y in the formula is the apparent density (g/cm.sup.3) of the ferrite particle.

The present disclosure is directed to methods of Quantum Spin Engineering of spinel superparamagnetic ferrite nanoparticles (SMFNs) for MRI contrast agents and for magnetohyperthermia agents. Using the methods herein, the magnetic properties of the SMFNs can be controlled by changing the amount of 3d-transition element cations having unpaired electrons in the 3d orbital that occupy the octahedral sites of the spinel crystal form, to form mixed spinels, while anions in the spinels can be utilized to magnetically couple the cations utilizing intra-crystalline angles determined by ion sizes and crystal structure, and further tuning of other critical parameters is provided. The mixed spinels disclosed herein provide enhanced MRI contrast agents and improved magnetohyperthermia agents with lower toxicity and safety concerns, while the production methods disclosed herein have lower cost.

A ferrite sintered body contains Fe, Mn, Zn, Cu, and Ni. Supposing that Fe, Mn, Zn, Cu, and Ni are converted into Fe.sub.2O.sub.3, Mn.sub.2O.sub.3, ZnO, CuO, and NiO, respectively, and the sum of the contents of Fe.sub.2O.sub.3, Mn.sub.2O.sub.3, ZnO, CuO, and NiO is 100 mol %, the sum of the contents of Fe.sub.2O.sub.3 and Mn.sub.2O.sub.3 is 48.47 mol % to 49.93 mol %, the content of Mn.sub.2O.sub.3 is 0.07 mol % to 0.37 mol %, the content of ZnO is 28.95 mol % to 33.50 mol %, and the content of CuO is 2.98 mol % to 6.05 mol %. Furthermore, 102 ppm to 4,010 ppm Zr in terms of ZrO.sub.2 and 10 ppm to 220 ppm Al in terms of Al.sub.2O.sub.3 are contained per 100 parts by weight of the sum of the amounts of contained Fe.sub.2O.sub.3, Mn.sub.2O.sub.3, ZnO, CuO, and NiO.

The present invention provides: a ferrite particle containing a crystal phase component containing a perovskite crystal represented by the compositional formula RZrO.sub.3 (where R is an alkaline earth metal element); and an electrophotographic developer carrier core material, an electrophotographic developer carrier, and an electrophotographic developer containing the ferrite particles.

A ferrite sintered body contains Fe, Mn, Zn, Cu, and Ni. Supposing that Fe, Mn, Zn, Cu, and Ni are converted into Fe.sub.2O.sub.3, Mn.sub.2O.sub.3, ZnO, CuO, and NiO, respectively, and the sum of the contents of Fe.sub.2O.sub.3, Mn.sub.2O.sub.3, ZnO, CuO, and NiO is 100 mol %, the sum of the contents of Fe.sub.2O.sub.3 and Mn.sub.2O.sub.3 is 48.47 mol % to 49.93 mol %, the content of Mn.sub.2O.sub.3 is 0.07 mol % to 0.37 mol %, the content of ZnO is 28.95 mol % to 33.50 mol %, and the content of CuO is 2.98 mol % to 6.05 mol %. Furthermore, 102 ppm to 4,010 ppm Zr in terms of ZrO.sub.2 and 10 ppm to 220 ppm Al in terms of Al.sub.2O.sub.3 are contained per 100 parts by weight of the sum of the amounts of contained Fe.sub.2O.sub.3, Mn.sub.2O.sub.3, ZnO, CuO, and NiO.

In an aspect, a ferrite composition comprises a RuCo.sub.2Z ferrite having the formula: (Ba.sub.3-xM.sub.x)Co.sub.2(MRu).sub.yFe.sub.24-2y-zO.sub.41, wherein M is at least one of Sr, Pb, or Ca; M is at least one of Co, Zn, Mg, or Cu; x is 1 to 3; y is greater than 0 to 2; and z is 4 to 4. In another aspect, an article comprises the ferrite composition. In yet another aspect, method of making the ferrite composition comprises mixing ferrite precursor compounds comprising Fe, Ba, Co, and Ru; and sintering the ferrite precursor compounds in an oxygen atmosphere to form the RuCo.sub.2Z ferrite.

A ferrite sintered body contains Fe, Mn, Zn, Cu, and Ni. Supposing that Fe, Mn, Zn, Cu, and Ni are converted into Fe.sub.2O.sub.3, Mn.sub.2O.sub.3, ZnO, CuO, and NiO, respectively, and the sum of the contents of Fe.sub.2O.sub.3, Mn.sub.2O.sub.3, ZnO, CuO, and NiO is 100 mol %, the sum of the contents of Fe.sub.2O.sub.3 and Mn.sub.2O.sub.3 is 48.47 mol % to 49.93 mol %, the content of Mn.sub.2O.sub.3 is 0.07 mol % to 0.37 mol %, the content of ZnO is 28.95 mol % to 33.50 mol %, and the content of CuO is 2.98 mol % to 6.05 mol %. Furthermore, 102 ppm to 4,010 ppm Zr in terms of ZrO.sub.2 and 10 ppm to 220 ppm Al in terms of Al.sub.2O.sub.3 are contained per 100 parts by weight of the sum of the amounts of contained Fe.sub.2O.sub.3, Mn.sub.2O.sub.3, ZnO, CuO, and NiO.