A ferrite composition includes a main component and a sub-component. The main component includes 10.0 to 38.0 mol % of a Fe compound in terms of Fe.sub.2O.sub.3, 3.0 to 11.0 mol % of a Cu compound in terms of CuO, 39.0 to 80.0 mol % (excluding 39.0 mol %) of a Zn compound in terms of ZnO, and a balance of a Ni compound. The sub-component includes 10.0 to 23.0 parts by weight of a Si compound in terms of SiO.sub.2, 0 to 3.0 parts by weight (including 0 parts by weight) of a Co compound in terms of Co.sub.3O.sub.4, and 0.1 to 3.0 parts by weight of a Bi compound in terms of Bi.sub.2O.sub.3 with respect to 100 parts by weight of the main component.

The present invention relates to a novel multi-layered zirconia dental blank comprising at least two reverse layers. Further, the invention relates to a process for the preparation of such a multi-layered zirconia dental blank. The invention also relates to the use of such a multi-layered zirconia dental blank for the production of a dental article. Preferred dental articles are artificial teeth, inlays, onlays, bridges, crowns, veneers, facings, crown frameworks, bridged frameworks, implants, abutments, copings or orthodontic appliances. Moreover, the invention relates to a process for producing a dental article out of such a multi-layered zirconia dental blank.

A ferrite sintered body contains from 48.2% by mole to 49.7% by mole Fe in terms of Fe.sub.2O.sub.3, from 2.0% by mole to 8.0% by mole Cu in terms of CuO, from 17.7% by mole to 24.0% by mole Ni in terms of NiO, and from 21.0% by mole to 28.0% by mole Zn in terms of ZnO, in which, when Fe, Cu, Ni, and Zn are converted to Fe.sub.2O.sub.3, CuO, NiO, and ZnO, respectively, and when the total amount of the Fe.sub.2O.sub.3, the CuO, the NiO, and the ZnO is 100 parts by weight, the ferrite sintered body contains from 5 ppm to 25 ppm B in terms of elemental B and from 6 ppm to 25 ppm Nb in terms of elemental Nb.

The present invention is related to a method for the manufacture of a multilayer blank, having a lowermost layer and a topmost layer, of a ceramic material, where layers of different compositions are introduced layer-by-layer into a mold, compressed and then sintered and where individual layers contain at least one coloring oxide, wherein as a first coloring oxide as the one coloring oxide at least one oxide from the group Co, Mn, Ni, Cr is used, the proportion of which in the lowermost layer containing the first coloring oxide is lower than in the topmost layer containing the first coloring oxide: and at least one oxide from the group Pr, Er, Fe, Ti, V, Bi, Cu, Tb is used as the second coloring oxide, the proportion of which in the lowermost layer containing the second coloring oxide is greater than that in the topmost layer.

When the porous ceramic structure contains Co together with Fe or Mn, the Co content is higher than or equal to 0.1 mass % and lower than or equal to 3.0 mass % in terms of Co.sub.3O.sub.4, and when the porous ceramic structure contains Co without containing Fe and Mn, the Co content is higher than or equal to 0.2 mass % and lower than or equal to 6.0 mass % in terms of Co.sub.3O.sub.4. The ratio of the sum of the Fe content in terms of Fe.sub.2O.sub.3, the Mn content in terms of Mn.sub.2O.sub.3, and the Co content in terms of Co.sub.3O.sub.4 to the Ce content in terms of CeO.sub.2 is higher than or equal to 0.8 and lower than or equal to 9.5.

A zirconia ceramic material for use in dental applications is provided comprising an yttria-stabilized zirconia material comprising from 4.5 mol % to 5.1 mol % yttria. Optionally, the zirconia ceramic has a coloring agent that may comprise one or more metals selected from terbium (Tb), chromium (Cr), erbium (Er), and cobalt (Co), and further, may, optionally, comprise alumina, which if present may be in an amount from 0 wt % to 0.25 wt %. The zirconia ceramic materials exhibit both enhanced translucency and a flexural strength of at least 800 MPa when fully sintered.

A ferrite sintered magnet including 0.010 mass % or more and 0.090 mass % or less of Mg in terms of MgO.

A ferrite composition includes a main component and a sub component. The main component includes an iron oxide in terms of Fe.sub.2O.sub.3, a copper oxide in terms of CuO, a zinc oxide in terms of ZnO, and a nickel oxide as its remainder. The sub component includes a cobalt oxide in terms of Co.sub.3O.sub.4, a tin oxide in terms of SnO.sub.2, and a bismuth oxide in terms of Bi.sub.2O.sub.3. A is −3.5 or more and 1.0 or less, provided that A=(α−18)/β; is defined, in which α is an amount of the zinc oxide represented by mol % in terms of ZnO in the main component, and β is an amount of the cobalt oxide represented by parts by weight in terms of Co.sub.3O.sub.4 with respect to 100 parts by weight of the main component.

A zirconia sintered body comprising 3.0 wt % or more and 30.0 wt % or less of aluminum in terms of Al.sub.2O.sub.3 and a remainder is zirconia containing 2 mol % or more and 4 mol % or less of erbia, in which the zirconia sintered body includes grains of aluminum oxide, and a total light transmittance with respect to a D65 light source at a sample thickness of 1.0 mm is 10% or less.

In an aspect, a Co.sub.2Z ferrite has the formula: (Ba.sub.1−xSr.sub.x).sub.3Co.sub.2+yM.sub.yFe.sub.24−2y−zO.sub.41. M is at least one of Mo, Ir, or Ru. The variable x can be 0 to 0.8, or 0.1 to 0.8. The variable y can be 0 to 0.8, or 0.01 to 0.8. The variable z can be −2 to 2. The Co.sub.2Z ferrite can have an average grain size of 5 to 100 nanometers, or 30 to 80, or 10 to 40 nanometers as measured using at least one of transmission electron microscopy, field emission scanning electron microscopy, or x-ray diffraction.