Method of producing zinc molybdate monocrystals
SUBSTANCE: invention relates to growing high-temperature inorganic monocrystals and can be used in quantum electronics and elementary-particle physics, in particular for neutrinoless double beta decay detectors. The said monocrystals are grown by pulling zinc molybdate crystals ZnMoO4 from molten initial charge in a melting pot for inoculation. The initial charge used is a mixture of oxides ZnO and MoO3, taken in stoichiometric ratio with excess MoO3 in amount of 1.0-7.0 wt %, and growth takes place at crystallisation volume rate of over 0.4 cm3/h. Using Czochralski growth method, pulling rate is 0.3-3.0 mm/h with axial temperature gradient at the crystallisation front of 80-100°/cm. Using Kyropoulos growth method, pulling rate does not exceed 0.5 mm/h while maintaining crystal diametre of 80-95 % of the diametre of the melting pot.
EFFECT: proposed method allows for obtaining large monocrystals (size of 1 cm3 or more), with optical properties suitable for use as scintillation detectors and optical elements.
3 cl, 2 ex, 2 dwg
The invention relates to single crystal growth, namely the cultivation of high-temperature inorganic single crystals, and can be used in quantum electronics and the physics of elementary particles, in particular, for the creation of the detectors of the process of neutrinoless double beta decay.
Closest to the invention is the method described in the article [Abe, Milliman, Caseview, Agustien, Vggismo, "Electron paramagnetic resonance and crystal structure of the molybdate zinc ZnMoO4". Journal of structural chemistry, t.20, No. 3, s-455 (1979)], in which the crystals for studies were grown by the Czochralski method from a melt at atmospheric pressure. However, the investigated crystals have sizes of the order of 2-5 mm, insufficient for use in scintillation detectors. This circumstance determines the main disadvantage of the above method.
The technical result of the invention is to obtain large single crystals ZnMoO4(the size of 1 cm or more)with optical quality, suitable for use as scintillation detectors and optical elements.
The technical result is achieved by a method of growing single crystals of zinc molybdate ZnMoO4from the melt of the source of the charge in the crucible pulling on a rotating seed. The way otlicials the same time, as the original mixture, a mixture of the oxides ZnO, Moo3taken in stoichiometric ratio with excess MoO3in the amount of from 1.0 to 7.0 wt.% corsehill to compensate for the loss of molybdenum oxide, resulting from evaporation in the process of growth. The choice of intervals concentrations caused by the crystallization conditions (temperature gradients in the crystallization zone, the area of the free surface of the melt, the duration of the growth process). According to the obtained experimental data, the rate of evaporation of Moo3when the temperature of the crystal growth is 0.025 g/h·cm2. When the concentration of the MoO3in the melt is less than 1.0 wt.% or above 7.0 wt.% corsehill the growth of the polycrystal. The cultivation is carried out at flow rate of crystallization of not more than 0,40 cm3/PM
When grown by the Czochralski method, the speed of extrusion is 0.3-3.0 mm/h when the axial temperature gradient at the crystallization front 80-100°/see
When Versiliana using the kyropoulos method, the speed of extrusion is not more than 0.5 mm/HR while maintaining the diameter of the crystal from 80 to 95% of the diameter of the crucible.
The method is illustrated by figure 1 and figure 2.
Figure 1 shows pictures of single crystals of zinc molybdate, grown by Czochralski method (a) and using the kyropoulos method (b). Figure 2 shows the received time-resolved emission spectra of zinc molybdates, lithium-zinc and magnesium under excitation by synchrotron radiation (wavelength 290 nm) at a temperature of 10K.
Example 1. The initial charge is prepared from a mixture of components ZnO and MoO3(both brand OFS), taken in a molar ratio of 1:1, by the method of solid-phase synthesis at 700°C for 6 hours in a platinum Cup in the furnace of resistance to the air. The melting of the charge produced in a platinum crucible, which is placed in a growth chamber "Crystal-3M with high-frequency heating. The process of growing crystal is carried out in air at atmospheric pressure. The molten zinc molybdate get at a temperature of 1003±5°C. Then the temperature was slightly lower and conduct seeding and growing a crystal on a seed crystal with the speed of extrusion of 0.3-3.0 mm/h, rotation speed 1-100 rpm and an axial temperature gradient at the crystallization front 80-1007 see the Speed of extrusion is selected to match the diameter of the crystal so that it does not exceed the optimum volumetric crystallization rate of 0.40 cm3/H. With an axial temperature gradient of 100°/cm bulk crystallization rate must be reduced in order to avoid formation in crystal growth defects (scattering centers, inclusions and cracks). At low temperature gradients, it is difficult to maintain a stable diameter of the growing crystal, the manufacturability p is ocess reduced. Data for examples 1-5 implementation of the method of producing single crystals of zinc molybdate in the table. After completion of the growth process, the crystal separated from the melt and hold pokerstove annealing with a gradual decrease of temperature in the growth chamber in 6-12 hours. The crystal is removed from the growth chamber after cooling is complete.
Example 2. The initial charge is prepared from a mixture of components ZnO and MoO3(both brand OFS), taken in a molar ratio of 1:1, by the method of solid-phase synthesis at 700°C for 6 hours in a platinum Cup in the furnace of resistance to the air. The melting of the charge produced in a platinum crucible, which is placed in a growth chamber "Crystal-3M with high-frequency heating. The process of growing crystal is carried out in air at atmospheric pressure. The molten zinc molybdate get at a temperature of 1003±5°C. Then the temperature was slightly lower and conduct seeding and growing a crystal on a seed crystal with the speed of extrusion is not more than 0.5 mm/h and speed 1-100 rpm, the diameter of the crystal support from 80 to 95% of the diameter of the crucible (kyropoulos method). Maintaining the diameter of the growing crystal is close to the diameter of the crucible provides a small amount of the free surface of the melt from which the evaporation MoO3. The concentration of the excess of oxide of molyb the s in the melt in this case can be reduced to 2.0 wt.% while maintaining the stoichiometric composition of the growing crystal. The probability of occurrence of inclusions of foreign phases in the growing crystal is reduced.
From the grown single crystals were produced samples of size 10×10×1(5) mm, their surfaces polished. By the method of x-ray microanalysis confirmed the phase composition - ZnMoO4. Optical quality is characterized by the absence of bubbles, cracks, inclusions of foreign phases, transparency in the region from 330 to 3100 nm. The crystals have a diffuse absorption band with maximum at 445 nm. Color crystals - dark orange.
Method of x-ray analysis determined the lattice parameters of the grown crystals - a=9.6850Å, b=6.9691Å, c=8.3705Å, α=96.74°, β=106.87°, γ=101.73°, which is consistent with literature data (a=9.625, b=6.965, c=8.373, α=96°18', β=103°18' [Lindemanis, Why, Avechicago, Nvelo, "On the crystal chemistry of isomorphic substitutions in the molybdates and wolframates divalent metals". Inorganic materials, Vol.3, No. 12, s-2234 (1967)]).
|No.||The composition of the melt||V, mm/h||ω, rpm||Annealing, h||Parameters crystal||The volumetric rate of crystallization, cm3/h|
|1||ZnMoO4||5||30||6||⌀0=13 mm, 1=40 mm||0,66||Polycrystal|
|2||ZnMoO4||3,0||3||30||6||⌀0=10 mm, 1=21 mm||0,23||Transparent. Without cracks and inclusions|
|3||ZnMoO4||5,0||3||30||6||⌀0=13 mm, 1=36 mm||0,39||Transparent. Without cracks and inclusions|
|4||ZnMoO4||6,5||3||30||8||⌀0=10 mm, 1=40 mm||0,23||Transparent. On the treatment center|
|5||ZnMoO4||2,0||0,3||5||12||⌀0=32 mm, 1=21 mm||0,24||Transparent|
The spectral-luminescent properties of the obtained crystals ZnMoO4. The spectra of reflection and excitation luminescence under excitation by synchrotron radiation, defined the band's own luminescence with maximum at 610 nm.
Thus, the technical and economic efficiency of the proposed method of obtaining single crystals of zinc molybdate compared with the prototype is as follows:
- grown large single crystals of zinc molybdate with a diameter of 30 mm, length 40 mm, compared to 1-2 mm from the prototype;
- no radioactive isotopes of zinc in ZnMoO4avoids interference when registering for the neutrinoless double beta decay;
- the intensity of the luminescence of zinc molybdate higher than other crystals molybdates, not creating interference at check - in Li2Zn(MoO4)2and MgMoO4.
1. Method of growing single crystals of zinc molybdate ZnMoO4from the melt of the source of the charge in the crucible pulling the seed crystal, characterized in that the quality is TBE source blend a mixture of the oxides ZnO and MoO 3taken in stoichiometric ratio with excess MoO3in the amount of from 1.0 to 7.0 wt.% in excess of stoichiometry, and the cultivation is carried out at flow rate of crystallization of not more than 0.4 cm3/PM
2. The method according to claim 1, wherein the cultivation is performed by the Czochralski method with the speed of extrusion of 0.3-3.0 mm/h at the axial temperature gradient at the crystallization front 80-100°/see
3. The method according to claim 1, wherein the cultivation is performed by the kyropoulos method with the speed of extrusion is not more than 0.5 mm/h while maintaining the diameter of the crystal from 80 to 95% of the diameter of the crucible.
SUBSTANCE: invention relates to the process of refractory single crystal growing, particularly, sapphire, ruby, from melt with usage of seed crystal. Device includes two-sectional chamber 1, in top section of which it is located mobile by vertical water-cooled guide bar 4 with seed-holder 5, and in bottom section it is installed crucible 2 on support. Furnace in the form of two-sectional heater is formed from U-shaped solder pads, collected and bended by shape of crucible, top ands of which are fixed in annular current leads 13, located co-axial relative to vertical axis of whole device. Sections of chamber 1 are divided by set of attachable shields 9 with central hole for pass of water-cooled guide bar 4 with seed-holder 5, installed on top edges of crucible 2, and heater is implemented from tungsten rods, allowing different thickness in top 11 and bottom 12 sections so that cross-section area of tungsten rods of top sections 11 of heater, located higher the crucible level 2, exceed not less than two times cross-section area of tungsten rods of bottom section 12 of heater, enveloping outside crucible surface 2, herewith elements of top and bottom sections of heater forms united U-shaped solder pads. On current leads 13, installed on the top of two-sectional chamber, there are fixed from above through the electrical insulating insertion pieces 14 holders 15 of hanging shields 16, implemented in the form of set of horizontal molybdenum plates of annular strap and located in top section of growth station between water-cooled guide bar 4 and top section 11 of heater.
EFFECT: device design simplification, provides ability of creation of convex crystallisation front, creates conditions of reduction amount of boils in crystal that in the long run, provides receiving of large crystals of high optical quality with homogeneous structure at saving of electricity consumption during the growing process.
2 cl, 1 dwg
SUBSTANCE: invention is related to the field of single crystals growing from melts and may be used in enterprises of chemical and electronic industry for growing of sapphire single crystals of 1-6 quality category by Kyropulos method from melts on seed crystal. Method includes preparation of charge, its loading and melting by means of heating element in vacuum, seeding and pulling of single crystal, at that growing of single crystal is carried out to seed of technical quality of 6 category, which contains gas inclusions with size of up to 500 mcm and their accumulation, by means of seed crystal lowering by 10 mm every 10-12 minutes until it touches melt with temperature of 2330 K, which has no nucleation centers on the surface, seed crystal submersion for 20-30 sec in melt at 10-15 mm, lowering of heating element power until melt supercooling, which is required for nucleation of crystallisation grains on seed crystal surface in process of constrictions growth, and formation of cone-shaped convex crystallisation front in direction of melt.
EFFECT: growth of sapphire single crystals of optical quality on seed crystal of technical quality with content of gas inclusions and their clusters with diameter of up to 500 mcm, which makes it possible to reduce prime cost of single-crystal sapphire.
SUBSTANCE: invention concerns technique of receiving single crystal field by means of method of growth from melt. Method of furnace feed additional charging at growing of silicon single crystals by means of Czochralski method includes charge feeding on the melt surface in capsule from container with charged furnace feeding, where it is provided ability of charge feeding dose on the melt surface through the bottom end, dumping of container till the melt surface in capsule, melt temperature pulldown till formation on the surface of viscous layer of melt, interfere with feeding of unfused charge into melt volume, after what container is opened and charge portion is poured onto viscous layer surface. Then melt temperature is gradually applied till total melting of charged furnace feed, after what empty (or partially discharged) container is taken out from the growth region, to its place it is dropped rod with seed single crystal, it is implemented ingot dummy bar and implemented another silicon single crystals growth process.
EFFECT: higher parameters repeatability of grown ingots, and also reducing of growing of single crystals production cycle duration and energy saving at the expense of technological cycle optimisation.
SUBSTANCE: invention refers to borate-based material production technology for crystal growing from caesium borate or caesium-lithium borate which can be used as optical devices for wavelength transformation, in particular, laser generator. Method of crystal growing from caesium borate or caesium-lithium borate includes water dissolution of water-soluble caesium compound and water-soluble boron compound to produce aqueous solution, water evaporation from aqueous solution with or without baking to produce material for crystal growing, and melting of produced material to grow crystals from caesium borate. To grow crystals from caesium-lithium borate water-soluble caesium, lithium and boron compounds are used as initial components of raw material for growing.
EFFECT: invention allows for crystals grown from borate with excellent uniformity and reliability, with small consumptions and for the short period of time; besides, use of this crystal as optical device for wavelength transformation makes it possible to produce very reliable laser generator (laser oscillator).
13 cl, 4 ex, 21 dwg