A nonlinear optical crystal of cesium fluorooxoborate, and a method of preparation and use thereof. The crystal has a chemical formula of CsB.sub.4O.sub.6F and a molecular weight of 291.15. It belongs to an orthorhombic crystal system, with a space group of Pna2.sub.1, crystal cell parameters of a=7.9241 , b=11.3996 , c=6.6638 , and ===90, and a unit cell volume of 601.95 .sup.3. A melt method, high temperature solution method, vacuum encapsulation method, hydrothermal method or room temperature solution method is used to grow the crystal of CsB.sub.4O.sub.6F.

This invention provides a transparent magnetooptical material that is suitable for use in a magnetooptical device such as an optical isolator. Said magnetooptical material comprises either a transparent ceramic consisting primarily of a complex oxide that can be represented by formula (1) or a single crystal of such a complex oxide. Said magnetooptical material does not absorb fiber-laser light in the 0.9-1.1 m wavelength range, does not cause heat lensing, and has a higher Verdet constant than TGG crystals, with a Verdet constant of at least 0.14 min/(Oe.Math.cm) at a wavelength of 1,064 nm.
Tb.sub.2R.sub.2O.sub.7(1)
(In formula (1), R represents one or more elements selected from among the group consisting of silicon, germanium, titanium, tantalum, tin, hafnium, and zirconium (but not silicon only, germanium only, or tantalum only)).

This invention provides a transparent magnetooptical material that is suitable for use in a magnetooptical device such as an optical isolator. Said magnetooptical material comprises either a transparent ceramic consisting primarily of a complex oxide that can be represented by formula (1) or a single crystal of such a complex oxide. Said magnetooptical material does not absorb fiber-laser light in the 0.9-1.1 m wavelength range, does not cause heat lensing, and has a higher Verdet constant than TGG crystals, with a Verdet constant of at least 0.14 min/(Oe.Math.cm) at a wavelength of 1,064 nm.
Tb.sub.2R.sub.2O.sub.7(1)
(In formula (1), R represents one or more elements selected from among the group consisting of silicon, germanium, titanium, tantalum, tin, hafnium, and zirconium (but not silicon only, germanium only, or tantalum only)).

Preparations of a highly coherent diamond nitrogen vacancy (NV.sup.) and a diamond anvil are provided. A graphite is used as a carbon source, a diamond is used as a crystal seed, aluminum/titanium is used as a nitrogen remover, and a single crystal diamond is synthesized under a high temperature and a high pressure, and high-pressure-high-temperature (HPHT) annealing is performed on the synthesized diamond; after the annealing, multiple NV.sup.s are generated in <100> and <311> crystal orientation growth regions from scratch, while native NV.sup.s in a <111> crystal orientation growth region are disappeared; and the <100> and <311> crystal orientation growth regions do not contain defects related to ferromagnetic elements. The high-density and highly coherent NV.sup.s are produced under nondestructive conditions, and the diamond anvil with controlled NV.sup. depths are prepared to achieve a precise detection of the NV.sup. at a pressure above 60 GPa.

Preparations of a highly coherent diamond nitrogen vacancy (NV.sup.) and a diamond anvil are provided. A graphite is used as a carbon source, a diamond is used as a crystal seed, aluminum/titanium is used as a nitrogen remover, and a single crystal diamond is synthesized under a high temperature and a high pressure, and high-pressure-high-temperature (HPHT) annealing is performed on the synthesized diamond; after the annealing, multiple NV.sup.s are generated in <100> and <311> crystal orientation growth regions from scratch, while native NV.sup.s in a <111> crystal orientation growth region are disappeared; and the <100> and <311> crystal orientation growth regions do not contain defects related to ferromagnetic elements. The high-density and highly coherent NV.sup.s are produced under nondestructive conditions, and the diamond anvil with controlled NV.sup. depths are prepared to achieve a precise detection of the NV.sup. at a pressure above 60 GPa.

The present disclosure discloses a gradient single-crystal positive electrode material, which has a chemical formula of LiNi.sub.xCo.sub.yA.sub.1-x-yO.sub.2@mLi.sub.aZ.sub.bO.sub.c, wherein 0<x<1, 0<y<1, 0<x+y<1, 0<m<0.05, 0.3<a?10, 1?b<4, and 1?c<15, A is at least one of Mn, Zr, Sr, Ba, W, Ti, Al, Mg, Y, and Nb, and Z is at least one of B, Al, Co, W, Ti, Zr, and Si. The atomic ratio of the content of Co on the surface of the single-crystal positive electrode material particle to the content of Ni+Co+A on the surface is greater than 0.4 and less than 0.8, and the atomic ratio of Co at a depth 10% of the radius from the surface of the single crystal positive electrode material particle is not less than 0.3; and the single-crystal positive electrode material particle has a roundness of greater than 0.4, and is free from sharp corners.

The present disclosure discloses a gradient single-crystal positive electrode material, which has a chemical formula of LiNi.sub.xCo.sub.yA.sub.1-x-yO.sub.2@mLi.sub.aZ.sub.bO.sub.c, wherein 0<x<1, 0<y<1, 0<x+y<1, 0<m<0.05, 0.3<a?10, 1?b<4, and 1?c<15, A is at least one of Mn, Zr, Sr, Ba, W, Ti, Al, Mg, Y, and Nb, and Z is at least one of B, Al, Co, W, Ti, Zr, and Si. The atomic ratio of the content of Co on the surface of the single-crystal positive electrode material particle to the content of Ni+Co+A on the surface is greater than 0.4 and less than 0.8, and the atomic ratio of Co at a depth 10% of the radius from the surface of the single crystal positive electrode material particle is not less than 0.3; and the single-crystal positive electrode material particle has a roundness of greater than 0.4, and is free from sharp corners.

A single crystal multi-element positive electrode material and a preparation method therefor, and a lithium ion battery. The ratio of the length of the longest diagonal line to the length of the shortest diagonal line of the single crystal particles of the single crystal multi-element positive electrode material measured by an SEM is roundness R, and R?1; and D.sub.10, D.sub.50 and D.sub.90 of the single crystal particles of the single crystal multi-element positive electrode material satisfy: K.sub.90=(D.sub.90?D.sub.10)/D.sub.50, and the product of K.sub.90 and R is 1.20-1.40. The single crystal multi-element positive electrode material is more round and regular in morphology, the single crystal particles have uniform size, less agglomeration and less adhesion. The material has the characteristics of high compaction density, good rate capability and excellent cycle performance.

A single crystal multi-element positive electrode material and a preparation method therefor, and a lithium ion battery. The ratio of the length of the longest diagonal line to the length of the shortest diagonal line of the single crystal particles of the single crystal multi-element positive electrode material measured by an SEM is roundness R, and R?1; and D.sub.10, D.sub.50 and D.sub.90 of the single crystal particles of the single crystal multi-element positive electrode material satisfy: K.sub.90=(D.sub.90?D.sub.10)/D.sub.50, and the product of K.sub.90 and R is 1.20-1.40. The single crystal multi-element positive electrode material is more round and regular in morphology, the single crystal particles have uniform size, less agglomeration and less adhesion. The material has the characteristics of high compaction density, good rate capability and excellent cycle performance.

An oriented alumina substrate for epitaxial growth according to an embodiment of the present invention includes crystalline grains constituting a surface thereof, the crystalline grains having a tilt angle of 1 or more and 3 or less and an average sintered grain size of 20 m or more.