A composite polycrystal includes: a polycrystalline diamond phase including a plurality of diamond particles; and non-diamond phases composed of non-diamond carbon. The non-diamond phases are distributed in the polycrystalline diamond phase. An average value of projected area equivalent circle diameters of the non-diamond phases is not more than 1000 nm.

An oriented ceramic sintered body production method includes (a) a step of preparing a ceramic compact before firing into an oriented ceramic sintered body; and (b) a step of obtaining an oriented ceramic sintered body by sandwiching the ceramic compact between a pair of releasing sheets, placing the ceramic compact and the releasing sheets in a hot press firing furnace, and hot press firing the ceramic compact while applying a pressure by a pair of punches through the pair of releasing sheets, wherein each of the releasing sheets is a releasing sheet such that, after the releasing sheet is sandwiched between PET films, is then placed and vacuum-packed on a stainless steel sheet, and is isostatically pressed at 200 kg/cm.sup.2, a surface of the releasing sheet on the side opposite from the stainless steel sheet has a profile curve with a total profile height Pt of 0.8 ?m or less.

A method of fabricating a ceramic molded body for sintering, which includes molding a raw material powder containing a ceramic powder and a thermoplastic resin having a glass transition temperature higher than room temperature into a predetermined shape by isostatic pressing and in which a first-stage press-molded body is fabricated by subjecting a uniaxially press-molded body fabricated by uniaxially pressing the raw material powder into a predetermined shape or the raw material powder filled in a rubber die to a first-stage isostatic press molding at a temperature lower than a glass transition temperature of the thermoplastic resin and then a ceramic molded body is fabricated by heating this first-stage press-molded body to a temperature equal to or higher than the glass transition temperature of the thermoplastic resin and performing warm isostatic press molding as second-stage isostatic press molding.

An article comprises a first member comprising a first carbon composite; and a second member disposed on the first member and comprising a second carbon composite and a reinforcing agent, wherein the second member has a gradient in the weight ratio of the second carbon composite to the reinforcing agent, and wherein the first member has one or more of the following properties different than those of the second member: elasticity; corrosion resistance; erosion resistance; or hardness.

A method comprising the steps of mixing raw material powders to a composition comprising metal elements of Ca, La, Sr, Ba, Fe and Co, whose atomic ratios are represented by the general formula of Ca.sub.1-x-yLa.sub.x(Sr.sub.yBa.sub.1-y).sub.yFe.sub.2n-zCo.sub.z, wherein 1xy, x and y are values in a region defined by a coordinate a: (0.470, 0.297, 0.233), a coordinate b: (0.300, 0.392, 0.308), a coordinate c: (0.300, 0.300, 0.400), a coordinate d: (0.400, 0.200, 0.400) and a coordinate e: (0.470, 0.200, 0.330) in a ternary diagram of x, y, and 1xy, y and z, and n representing a molar ratio meet 0.5y1, 0.2z<0.25, and 5.2<n<5.6; calcining the raw material powder mixture; pulverizing the calcined body; molding the calcined powder; and sintering the resultant green body; 0.1% or more and less than 1.5% by mass of SiO.sub.2 being added to the raw material powder mixture, the calcined body or the calcined powder; and 0-2% by mass (as CaO) of CaCO.sub.3 being added to the calcined body or the calcined powder.