A zirconia sintered body is provided in which the strength between layers of powders is improved. A flexural strength of a test sample of the zirconia sintered body, measured pursuant to JISR1601, is not less than 1000 MPa. The test sample is formed by preparing a plurality of zirconia powders, each containing zirconia and preferably yttria as a stabilizer that suppresses phase transition of zirconia, the zirconia powders differing in a composition, layering the zirconia powders to form a zirconia composition, and sintering the zirconia composition to form a zirconia sintered body. The flexural strength is measured such that a load point is positioned at a boundary of the zirconia powders, the boundary traversing the test sample of the sintered body along a direction of load application.

A zirconia pre-sintered body suitable for dental milling, grinding and/or cutting can provide a sintered body in which the strength between layers of powders is improved. A flexural strength of a test sample of the zirconia sintered body, measured pursuant to JISR1601, is preferably not less than 1000 or 1100 MPa.

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.

A sintered body includes a solid solution containing cobalt and iron, with the balance being zirconia. The total content of cobalt in terms of CoO and iron in terms of Fe.sub.2O.sub.3 is more than 0.1 wt % and less than 3.0 wt %, and the proportion of cobalt regions larger than 5.5 μm.sup.2 in an elemental map obtained using an electron probe microanalyzer is 25% or less.

The light shielding member of the present disclosure includes an aluminum oxide ceramics including an oxide of titanium whose composition formula is shown as TiO.sub.2-x (1≤x<2), and a total content of Fe, Ni, Co, Mn and Cr is 260 mass ppm or less.

A process for preparing roofing granules includes forming kaolin clay into green granules and sintering the green granules at a temperature of at least 900 degrees Celsius to cure the green granules until the crystalline content of the sintered granules is at least ten percent as determined by x-ray diffraction.

A dental zirconia system to produce translucent zirconia sintered bodies comprises at least two separate zirconia green bodies. At least one zirconia green body comprises zirconium oxide and a lower content of at least one other oxide summing to between 6.5 wt % to 20 wt % based on a total weight percent of the zirconia green body. At least another zirconia green body comprises zirconium oxide and a higher content of at least one other oxide summing to between 7.5 wt % to 20 wt % based on a total weight percent of the zirconia green body. The at least two zirconia green bodies each have at least some particles with a diameter of 100 nanometers to 1000 nanometers. The at least two zirconia green bodies have different amounts of the at least one other oxide with respect to one another.

A process for improving the grade and optical quality of zircon, comprising: baking a mixture of a zircon feed and concentrated sulphuric acid at a baking temperature in the range of from 200 up to 400° C., and for a time to form water leachable sulphates with impurities therein including at least iron and titanium; leaching the baked mixture to dissolve the leachable sulphates; and separating the zircon from the leachate containing the leached sulphates, which separated zircon is thereby of improved grade and optical quality.

A zirconia composition, a zirconia semi-sintered body, a zirconia sintered body, and a dental product are provided. The zirconia sintered body contains 4 mol % to 7 mol % of yttria as stabilizer, and a shielding material. The zirconia sintered body comprises first region and second region having a higher content ratio of the shielding material than the first region. Difference between content ratio of yttria in the first region and that of yttria in the second region is 1 mol % or less.

The invention relates to a method for the preparation of a blank from a ceramic material, wherein at least two layers of ceramic material of different compositions are filled into a die layer-by-layer and after filling of the layers they are then pressed and sintered, wherein after filling of a first layer this is structured on its surface in such a way that the first layer, viewed across its surface, differs in its height from region to region, and then a layer with a composition that differs from the first layer is filled as a second layer into the mold.