The present invention provides a lead-free piezoelectric material having a high piezoelectric constant and a high mechanical quality factor in a wide operating temperature range. The piezoelectric material includes a perovskite-type metal oxide represented by Formula (1):
(Ba.sub.1-xCa.sub.x).sub.a(Ti.sub.1-yZr.sub.y)O.sub.3 (1.00≦a≦1.01, 0.125≦x<0.155, and 0.041≦y≦0.074)
as a main component. The metal oxide contains Mn in a content of 0.12 parts by weight or more and 0.40 parts by weight or less based on 100 parts by weight of the metal oxide on a metal basis.

An armor component including a body having a first portion including calcium boride compounds include non-stoichiometric calcium boride (CaB.sub.x) and stoichiometric calcium boride (CaB.sub.6) and having a density of at least about 80% theoretical density. In one aspect, the first portion can include a first phase comprising silicon carbide (SiC) and a second phase comprising calcium boride (CaB.sub.6). In another aspect, the first portion can further include a third phase comprising boron carbide (B.sub.4C).

Disclosed are a composite sintered body for a cutting tool and a cutting tool using the same. The composite sintered body for a cutting tool has enhanced heat conductivity and electrical conductivity to be strong against abrasion by heat and impact and to be capable of minimizing an influence on an edge during an Electrical Discharge Machine (EDM) operation.

A ceramic composite can include a first ceramic phase and a second ceramic phase. The first ceramic phase can include a silicon carbide. The second phase can include a boron carbide. In an embodiment, the silicon carbide in the first ceramic phase can have a grain size in a range of 0.8 to 200 microns. The first phase, the second phase, or both can further include a carbon. In another embodiment, at least one of the first ceramic phase and the second ceramic phase can have a median minimum width of at least 5 microns.

A method of manufacturing polycrystalline abrasive elements consisting of micron, sub-micron or nano-sized ultrahard abrasives dispersed in micron, sub-micron or nano-sized matrix materials. A plurality of ultrahard abrasive particles having vitreophilic surfaces are coated with a matrix precursor material in a refined colloidal process and then treated to render them suitable for sintering. The matrix precursor material can be converted to an oxide, nitride, carbide, oxynitride, oxycarbide, or carbonitride, or an elemental form thereof. The coated ultrahard abrasive particles are consolidated and sintered at a pressure and temperature at which they are crystallographically or thermodynamically stable.

A refractory, coarse ceramic product including at least one granular refractory material, has an open porosity of between 22 and 45 vol.-%, in particular of between 23 and 29 vol.-%, and a grain structure of the refractory material, wherein the medium grain size fraction with grain sizes of between 0.1 and 0.5 mm is 10 to 55 wt.-%, in particular 35 to 50 wt.-%, and wherein the remainder of the grain structure is a finest grain fraction with grain sizes of up to 0.1 mm and/or coarse-grain fraction with grain sizes of more than 0.5 mm.

Provided is a lead-free piezoelectric material having satisfactory piezoelectric constant and mechanical quality factor in a device driving temperature range (−30° C. to 50° C.) The piezoelectric material includes a main component containing a perovskite-type metal oxide represented by Formula 1, a first auxiliary component composed of Mn, and a second auxiliary component composed of Bi or Bi and Li. The content of Mn is 0.040 parts by weight or more and 0.500 parts by weight or less based on 100 parts by weight of the metal oxide on a metal basis. The content of Bi is 0.042 parts by weight or more and 0.850 parts by weight or less and the content of Li is 0.028 parts by weight or less (including 0 parts by weight) based on 100 parts by weight of the metal oxide on a metal basis. (Ba.sub.1-xCa.sub.x).sub.a(Ti.sub.1-yZr.sub.y)O.sub.3 . . . (1), wherein, 0.030≦x<0.090, 0.030≦y≦0.080, and 0.9860≦a≦1.0200.

There is provided a polycrystalline cubic boron nitride containing a cubic boron nitride at a content greater than or equal to 98.5% by volume, the polycrystalline cubic boron nitride having a dislocation density less than or equal to 8×10.sup.15/m.sup.2.

A sintered MnZn ferrite body containing main components comprising 53.30-53.80% by mol of Fe calculated as Fe.sub.2O.sub.3, 6.90-9.50% by mol Zn calculated as ZnO, and the balance of Mn calculated as MnO, and sub-components comprising 0.003-0.020 parts by mass of Si calculated as SiO.sub.2, more than 0 parts and 0.35 parts or less by mass of Ca calculated as CaCO.sub.3, 0.30-0.50 parts by mass of Co calculated as Co.sub.3O.sub.4, 0.03-0.10 parts by mass of Zr calculated as ZrO.sub.2, and 0-0.05 parts by mass of Ta calculated as Ta.sub.2O.sub.5, pre 100 parts by mass in total of the main components (calculated as the oxides), and having an average crystal grain size of 3 μm or more and less than 8 μm and a density of 4.65 g/cm.sup.3 or more.

A complex sintered body includes a lamination of a layer composed of a zirconia sintered body containing 0.5% or more by mole and less than 4% by mole of an oxide of cerium in terms of CeO.sub.2, 2% or more by mole and less than 6% by mole of yttria and 0.1% or more by mass and less than 2% by mass of an oxide of aluminum; and at least one of a layer composed of a zirconia-based sintered body containing 2.0% or more by mass and 20.0% or less by mass of an oxide of aluminum, and a layer composed of a zirconia-based sintered body containing 2% or more by mole and less than 6% by mole of yttria and a coloring agent.