A compound strontium fluoroborate, nonlinear optical crystal of strontium fluoroborate, preparation method thereof; the chemical formula of the compound is SrB5O7F3, its molecular weight is 310.67, and it is prepared by solid-state reaction; the chemical formula of the crystal is SrB5O7F3, its molecular weight is 310.67, the crystal is of the orthorhombic series, the space group is Ccm21, and the crystal cell parameters are=10.016(6) Å, b=8.654(6)(4) Å, c=8.103(5) Å, Z=4, and V=702.4(8) Å3. A SrB5O7F3 nonlinear optical crystal has uses in the preparation of a harmonic light output when doubling, tripling, quadrupling, quintupling, or sextupling the frequency of a 1064-nm fundamental-frequency light outputted by a Nd:YAG laser, or the generation of a deep-ultraviolet frequency doubling light output lower than 200 nm, or in the preparation of a frequency multiplier, upper or lower frequency converter, or an optical parametric oscillator.

The present disclosure provides a growth method of a high-temperature phase lanthanum borosilicate crystal, where the high-temperature phase lanthanum borosilicate crystal is a β-La.sub.1-yLn.sub.yBSiO.sub.5 crystal prepared by a high-temperature flux method; a composite flux system is (La.sub.1-yLn.sub.y)BO.sub.3—LiMoO.sub.4—SiO.sub.2—B.sub.2O.sub.3, and (La.sub.1-yLn.sub.y)BO.sub.3, LiMoO.sub.4, SiO.sub.2, and B.sub.2O.sub.3 in the system have molar percentages of x.sub.1, x.sub.2, x.sub.3, and x.sub.4, respectively; 0<x.sub.1<0.3, 0.7≤x.sub.2<1, 0<x.sub.3<0.3, x.sub.1+x.sub.2+x.sub.3=1, x.sub.1:x.sub.4=2:1 to 4:1. In the present disclosure, a difficulty is overcome in the crystal growth of β-LaBSiO.sub.5 due to phase transition. The crystal is an optical function material that does not undergo the phase transition during annealing and can exist stably at room temperature. The crystal is widely used in laser, terahertz, and other fields.

A method for preparing a large-size two-dimensional layered metal thiophosphate crystal includes the following steps: 1) weighing raw materials of indium spheres, phosphorous lumps and sulfur granules according to a predetermined amount and proportion, mixing them, and using iodine as a transport agent and potassium iodide as a molten salt; 2) adding the raw materials, the iodine and the potassium iodide to a reaction vessel together, and vacuum sealing it under a certain pressure, and then subjecting it to a high-temperature reaction; 3) taking out the products after the reaction, and washing the products to remove the residual iodine and potassium iodide and obtain large-size two-dimensional layered metal thiophosphate crystals. This method is simple and highly efficient.

The present invention provides a PZN-based large-size ternary high-performance single crystal, a growing method and a molten salt furnace. The PZN-based large-size ternary high-performance single crystal is represented by formula (1-x-y)Pb(B′.sub.1/2B″.sub.1/2)O.sub.3-yPb(Zn.sub.1/3Nb.sub.2/3)O.sub.3-xPbTiO.sub.3, wherein B′ is Mg, Fe, Sc, Ni, In, Yb, Lu and/or Ho, B″ is Nb, Ta and/or W, 0.4<x<0.6, 0.1<y<0.4, 0.1<1-x-y<0.4. The present invention adjusts the convective change of the melt through the rotation of the top seed and the bottom crucible, overcoming the problems of serious crystal inclusions and poor crystal quality during the growth process, and can adapt the change of the crystal diameter to the thermal inertia of the heat preservation system, thus effectively reducing crystal inclusions and improving the yield of the crystal.

The present invention provides a PZN-based large-size ternary high-performance single crystal, a growing method and a molten salt furnace. The PZN-based large-size ternary high-performance single crystal is represented by formula (1-x-y)Pb(B′.sub.1/2B″.sub.1/2)O.sub.3-yPb(Zn.sub.1/3Nb.sub.2/3)O.sub.3-xPbTiO.sub.3, wherein B′ is Mg, Fe, Sc, Ni, In, Yb, Lu and/or Ho, B″ is Nb, Ta and/or W, 0.4<x<0.6, 0.1<y<0.4, 0.1<1-x-y<0.4. The present invention adjusts the convective change of the melt through the rotation of the top seed and the bottom crucible, overcoming the problems of serious crystal inclusions and poor crystal quality during the growth process, and can adapt the change of the crystal diameter to the thermal inertia of the heat preservation system, thus effectively reducing crystal inclusions and improving the yield of the crystal.

A method of producing an apatite crystal includes the steps of preparing an apatite single crystal expressed by the general formula M.sup.2.sub.5(PO.sub.4).sub.3X (M.sup.2 being at least atomic element selected from the group consisting of divalent alkaline-earth metals and Eu, and X is at least one atomic selected from the group consisting of halogens); placing the apatite single crystal into a space controllable to a predetermined atmosphere; supplying water vapor into the space; and heating such that the atmosphere in the space is within a 1000° C. to 1400° C. range.

A crystal growth apparatus includes: a raw material supplying part that mixes raw materials including a group III element metal and an alkali metal; a growing part disposed at a stage under the raw material supplying part, the growing part having a seed substrate; a tilting mechanism that tilts the raw material supplying part and the growing part; a heater that heats the raw material supplying part and the growing part; a control part that controls an operation of the tilting mechanism; and a supply port that supplies a nitrogen element-containing substance to the growing part, wherein the raw material supplying part having an opening facing to the growing part, the opening being disposed at a bottom portion and one edge portion of the raw material supplying part, and the control part controls the tilting mechanism so as to tilt the raw material supplying part toward the other edge portion on the side opposite to the one edge portion so as to prevent the raw materials from entering the opening when the raw materials are mixed, and the control part controls the tilting mechanism so as to tilt the raw material supplying part toward the one edge portion so that the raw materials drop through the opening to the growing part when the mixing of the raw materials is completed.

A crystal growth apparatus includes: a raw material supplying part that mixes raw materials including a group III element metal and an alkali metal; a growing part disposed at a stage under the raw material supplying part, the growing part having a seed substrate; a tilting mechanism that tilts the raw material supplying part and the growing part; a heater that heats the raw material supplying part and the growing part; a control part that controls an operation of the tilting mechanism; and a supply port that supplies a nitrogen element-containing substance to the growing part, wherein the raw material supplying part having an opening facing to the growing part, the opening being disposed at a bottom portion and one edge portion of the raw material supplying part, and the control part controls the tilting mechanism so as to tilt the raw material supplying part toward the other edge portion on the side opposite to the one edge portion so as to prevent the raw materials from entering the opening when the raw materials are mixed, and the control part controls the tilting mechanism so as to tilt the raw material supplying part toward the one edge portion so that the raw materials drop through the opening to the growing part when the mixing of the raw materials is completed.

A self-supporting substrate includes a first nitride layer grown by hydride vapor deposition method or ammonothermal method and comprising a nitride of one or more element selected from the group consisting of gallium, aluminum and indium; and a second nitride layer grown by a sodium flux method on the first nitride layer and comprising a nitride of one or more element selected from the group consisting of gallium, aluminum and indium. The first nitride layer includes a plurality of single crystal grains arranged therein and being extended between a pair of main faces of the first nitride layer. The second nitride layer includes a plurality of single crystal grains arranged therein and being extended between a pair of main faces of the second nitride layer. The first nitride layer has a thickness larger than a thickness of the second nitride layer.

A self-supporting substrate includes a first nitride layer grown by hydride vapor deposition method or ammonothermal method and comprising a nitride of one or more element selected from the group consisting of gallium, aluminum and indium; and a second nitride layer grown by a sodium flux method on the first nitride layer and comprising a nitride of one or more element selected from the group consisting of gallium, aluminum and indium. The first nitride layer includes a plurality of single crystal grains arranged therein and being extended between a pair of main faces of the first nitride layer. The second nitride layer includes a plurality of single crystal grains arranged therein and being extended between a pair of main faces of the second nitride layer. The first nitride layer has a thickness larger than a thickness of the second nitride layer.