To provide a zirconia sintered body having both excellent translucency and bending strength, specifically a zirconia sintered body having both translucency and strength suitable as a denture for front tooth, and a process for its production. A translucent zirconia sintered body containing more than 4.0 mol % and at most 6.5 mol % of yttria and less than 0.1 wt % of alumina, and having a relative density of at least 99.82%, a total light transmittance of at least 37% and less than 40% to light with a wavelength of 600 nm at a thickness of 1.0 mm, and a bending strength of at least 500 MPa, and a process for its production.

The present invention relates to a positive electrode active material having improved capacity characteristic and life cycle characteristic, and a method of preparing the same, and specifically, to a positive electrode active material for a lithium secondary battery, wherein the positive electrode active material comprises a compound represented by Formula 1 above and allowing reversible intercalation/deintercalation of lithium, and from a crystal structure analysis of the positive electrode active material by a Rietveld method in which space group R-3m is used in a crystal structure model on the basis of an X-ray diffraction analysis, the thickness of MO slab is 2.1275 Å or less, the thickness of inter slab is 2.59 Å or greater, and the cation mixing ratio between Li and Ni is 0.5% or less, and a method of preparing the same.

Single crystals of a new noncentrosymmetric polar oxysulfide SrZn.sub.2S.sub.2O (s.g. Pmn2.sub.1) grown in a eutectic KF-KCl flux with unusual wurtzite-like slabs consisting of close-packed corrugated double layers of ZnS.sub.3O tetrahedra vertically separated from each other by Sr atoms and methods of making same.

Provided is a solid electrolyte material comprising Li, Y, Br, and I, wherein in an X-ray diffraction pattern in which Cu-Kα is used as a radiation source, peaks are present within all ranges of diffraction angles 2θ of 12.5° to 14.0°, 25.0° to 27.8°, 29.2° to 32.3°, 41.9° to 46.2°, 49.5° to 54.7°, and 51.9° to 57.5°.

The present application discloses a positive electrode active material satisfying the chemical formula L.sub.xNa.sub.yM.sub.zCu.sub.αFe.sub.βMn.sub.γO.sub.2+δ−0.5ηX.sub.η and a preparation method therefor, a sodium ion battery and an apparatus including such battery, wherein L is a doping element at alkali metal site, M is a doping element at transition metal site, and X is a doping element at oxygen site, 0≤x<0.35, 0.65≤y≤1, 0<α≤0.3, 0<β≤0.5, 0<γ≤0.5, −0.03≤δ≤0.03, 0≤η≤0.1, z+α+β+γ=1, mx+y+nz+2α+3β+4γ=2(2+δ), m is the valence state of L, and n is the valence state of M; and the pH of the positive electrode active material is 10.5-13, wherein L is a doping element at alkali metal site, M is a doping element at transition metal site, and X is a doping element at oxygen site.

A negative electrode active material according to one embodiment includes a titanium oxide compound having a crystal structure of monoclinic system titanium dioxide. The titanium oxide compound is modified by at least one kind of ion selected from the group consisting of an alkali metal cation, an alkali earth metal cation, a transition metal cation, a sulfide ion, a sulfuric acid ion and a chloride ion.

A sodium manganese composite oxide represented by Formula 1:
Na.sub.xMa.sub.yMn.sub.zMb.sub.vO.sub.2+d  Formula 1
wherein, 0.2≦x≦1, 0<y≦0.2, 0<z≦1, 0≦v<1, 0<z+v≦1, −0.3≦d<1, Ma is an electrochemically inactive metal, and Mb is different from Ma and Mn, and is at least one transition metal selected from elements in Groups 4 to 12 of the periodic table of the elements.

A layered oxide material, a preparation method, an electrode, a secondary battery and use are disclosed. The layered oxide material has a general chemical formula Na.sub.xCu.sub.iFe.sub.jMn.sub.kM.sub.yO.sub.2+β, in which M is an element that is doped for replacing the transition metals; x, y, i, j, k, and β are respectively the molar ratios of respective elements, provided that x, y, i, j, k, and β satisfy the relations: y+i++j+k=1, and x+my+2i+3j+4k=2(2+β), where 0.8≦x≦1, 0<i≦0.3, 0<j≦0.5, 0<k≦0.5, 0.02≦β≦0.02, and m is the valence of M. The layered oxide material has a space group of R3m.

A solid-state ion conductor includes a compound of Formula 1:

Li.sub.3a+b−(c*N)N.sub.aCl.sub.bX.sub.c  Formula 1

wherein, in Formula 1, X is an anion having an average oxidation state of n and is −3>n≤−1, and is at least one of Br, I, F, O, S, or P; and 1≤a≤4, 1≤b≤3, 0≤c≤3, and 4.8≤(a+b+c)≤5.2.

A method of producing a boron nitride polycrystal includes: a first step of obtaining a thermally treated powder by thermally treating a powder of a high pressure phase boron nitride at more than or equal to 1300° C.; and a second step of obtaining a boron nitride polycrystal by sintering the thermally treated powder under a condition of 8 to 20 GPa and 1200 to 2300° C.