CN113913937B - Lithium niobate crystal and preparation method thereof - Google Patents
Lithium niobate crystal and preparation method thereof Download PDFInfo
- Publication number
- CN113913937B CN113913937B CN202111022496.9A CN202111022496A CN113913937B CN 113913937 B CN113913937 B CN 113913937B CN 202111022496 A CN202111022496 A CN 202111022496A CN 113913937 B CN113913937 B CN 113913937B
- Authority
- CN
- China
- Prior art keywords
- lithium niobate
- crystal
- growth
- niobate crystal
- calculating
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
- C30B29/10—Inorganic compounds or compositions
- C30B29/16—Oxides
- C30B29/22—Complex oxides
- C30B29/30—Niobates; Vanadates; Tantalates
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B15/00—Single-crystal growth by pulling from a melt, e.g. Czochralski method
-
- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B28/00—Production of homogeneous polycrystalline material with defined structure
- C30B28/02—Production of homogeneous polycrystalline material with defined structure directly from the solid state
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Crystallography & Structural Chemistry (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Crystals, And After-Treatments Of Crystals (AREA)
Abstract
The application belongs to the technical field of photoelectric materials, and particularly relates to a lithium niobate crystal and a preparation method thereof. The preparation method of the lithium niobate crystal comprises the following steps: calculating a temperature field structure of lithium niobate crystal growth; calculating the growth parameters of lithium niobate crystals; mixing and drying a lithium source and a niobium source to obtain a mixed raw material; sintering the mixed raw materials in an air atmosphere to obtain a lithium niobate polycrystal block; in the calculated temperature field structure, after the lithium niobate polycrystal block is melted, under the guidance of seed crystal, crystal growth is carried out by adopting a pulling method according to the calculated growth parameters, and then the lithium niobate crystal is obtained. According to the preparation method of the lithium niobate crystal, the temperature field structure and the growth parameters of the lithium niobate crystal are calculated respectively through simulation, deduction and calculation methods, and then in the calculated temperature field structure, crystal growth is carried out by adopting a pulling method according to the calculated crystal growth parameters, so that the growth efficiency of the lithium niobate crystal is remarkably improved.
Description
Technical Field
The application belongs to the technical field of photoelectric materials, and particularly relates to a lithium niobate crystal and a preparation method thereof.
Background
The 5G is going forward in a broad step, and a new era of wide interconnection of everything and deep man-machine interaction is opened by a brand new network architecture. The RF front end is the core of mobile communication, and the filter can filter out-of-band interference and noise to meet the requirement of RF system and communication protocol for signal-to-noise ratio. Since the filter is susceptible to temperature variations, a temperature compensation film is added to the surface layer to improve the temperature characteristics of the SAW, and this temperature-compensated SAW filter is called a TC-SAW filter (Temperature compensated SAW). The high performance surface acoustic wave filter is required to have the characteristics of large bandwidth, high frequency, low insertion loss, small temperature coefficient of center frequency and the like. Among the plurality of substrate materials, lithium Niobate (LN) crystal materials are the first choice piezoelectric materials for selecting electric signals in each frequency band due to the advantages of large electromechanical coupling coefficient, large piezoelectric constant, high sound velocity and the like, and are indispensable key materials for forming TC-SAW filters. Meanwhile, the sound surface filter device is developed towards miniaturization, batch production and low cost, and the lithium niobate crystal material is required to be developed towards large size. Lithium niobate (LiNbO) 3 ) The crystal has excellent photoelectric, double refraction and nonlinear lightPhysical properties such as optical, acousto-optic, photoelastic, photorefractive, piezoelectric, pyroelectric, ferroelectric and photovoltaic effects; the composite material has stable mechanical performance, high temperature resistance, corrosion resistance, easy processing and low cost, and can show various special properties after doping. Therefore, lithium niobate crystals are known as "optical silicon".
The existing domestic lithium niobate/lithium tantalate products are mainly four inches and are supplemented with six inches. At present, lithium niobate crystals are mainly obtained by directly growing in air by using a Cz technology (Czochralski, czochralski method), wherein most of growing steps are high-frequency heating technology based on a platinum crucible, and the technical problems of difficult regulation of a temperature field of a growing interface, increased thermal stress of crystals and the like are faced, so that the crystals are easy to crack, and the yield is reduced. In addition, the slow growth speed increases the crystal growth period, increases the energy consumption, has insufficient productivity and high cost, and is difficult to meet the domestic market demand.
Disclosure of Invention
The invention aims to provide a lithium niobate crystal and a preparation method thereof, and aims to solve the problems of low process efficiency, high energy consumption and low yield of the existing large-size lithium niobate crystal to a certain extent.
In order to achieve the purposes of the application, the technical scheme adopted by the application is as follows:
in a first aspect, the present application provides a method for preparing lithium niobate crystals, comprising the steps of:
calculating a temperature field structure of lithium niobate crystal growth;
calculating the growth parameters of lithium niobate crystals;
mixing and drying a lithium source and a niobium source to obtain a mixed raw material;
sintering the mixed raw materials in an air atmosphere to obtain a lithium niobate polycrystal block;
and in the calculated temperature field structure, after the lithium niobate polycrystal block is melted, under the guidance of seed crystal, crystal growth is carried out by adopting a pulling method according to the calculated growth parameters, and then the lithium niobate crystal is obtained.
Further, the step of calculating a temperature field structure of lithium niobate crystal growth includes:
calculating a temperature gradient value in a crystal growth space in the growth process of the lithium niobate crystal;
and calculating the temperature field structure of the lithium niobate crystal according to the temperature gradient value, the thermal conductivity of the heat preservation material and the appearance structure of the heat preservation material.
Further, the step of calculating a temperature gradient value in a crystal growth space during the growth of the lithium niobate crystal includes:
assuming that the growth temperature field of the lithium niobate single crystal is a steady-state temperature field and has cylindrical symmetry, according to a heat transfer equation, the temperature expression is as shown in formula (III):
wherein r is,And z is the spatial variable of the crystal, T is the temperature;
establishing boundary conditions to obtain axial temperature gradient in the growth space of lithium niobate crystalAs shown in formula (IV); and radial temperature gradient in the growth space of lithium niobate crystals>As shown in formula (V);
wherein r is a Radius, theta, of lithium niobate crystal m As a function of the equilibrium temperature, h=ε/K, ε is the heat exchange coefficient, ε=ε 0 +ε R ，ε 0 Epsilon for convective heat exchange coefficient R Is the radiant heat exchange coefficient.
Further, the step of calculating the temperature field structure of the lithium niobate crystal growth includes:
calculating the thickness of the heat preservation layer and the appearance structure of the heat preservation material according to the geometric shape of the target lithium niobate crystal, the physical property of the lithium niobate crystal and the heat conductivity of the heat preservation material;
counting the melt center of the lithium niobate crystal and melt temperatures at a plurality of different positions away from the melt center according to the temperature gradient value, the thickness of the heat preservation layer and the appearance structure of the heat preservation material, and calculating radial temperature gradients; and calculating the axial temperature gradient by counting the melt center of the lithium niobate crystal and the environmental temperatures of a plurality of different positions vertically away from the melt center.
Further, the heat insulating material is at least one selected from siliceous heat insulating material, silicate heat insulating material, corundum heat insulating material, magnesium calcium heat insulating material, aluminum magnesium heat insulating material, magnesium siliceous heat insulating material and zirconium heat insulating material.
Further, the step of calculating the growth parameters of the lithium niobate crystal includes:
according to the rationale of chemical bonds for crystal growth, the anisotropic relative growth rate of lithium niobate crystals is calculated with reference to formula (I):
wherein R is uvw Is a lithium niobate crystal edge [ uvw ]]The relative growth rate in the direction, K, is the rate constant,is edge [ uvw]Chemical bonding energy of directional growth, A uvw For growing primitive edges [ uvw]Projected area of direction d uvw Is a lithium niobate crystal edge [ uvw ]]The step height in the direction;
determining the maximum thermodynamic growth rate of different pulling growth directions according to the anisotropic relative growth rate and lattice energy data of the lithium niobate crystal;
determining the pulling growth direction of the lithium niobate crystal, and obtaining the thermodynamic growth rate of the corresponding growth direction;
and calculating the pulling growth rate of the lithium niobate crystal according to the diameter and the length of the lithium niobate crystal which is required to be grown.
Further, the step of calculating the pull-up growth rate of the lithium niobate crystal includes:
calculating the pull-up growth rate of the lithium niobate crystal according to the diameter and length of the lithium niobate crystal required to be grown and with reference to the formula (II):
wherein v is the pulling speed, K of the lithium niobate crystal s Thermal conductivity of crystal, dT/dx s Is the temperature gradient, K, of lithium niobate crystal L dT/dx is the thermal conductivity of the melt L Temperature gradient of melt ρ s Is the density of lithium niobate crystals, and L is the latent heat of solidification.
Further, the conditions for performing the sintering treatment on the mixed raw materials include: sintering treatment is carried out in an air atmosphere with the temperature of 700-1100 ℃.
Further, the step of performing crystal growth by the pulling method includes: after the lithium niobate polycrystal block is melted and the characteristic liquid flow line appears, the seed crystal with a specific growth direction is used for carrying out seeding operation according to the calculated growth parameters, and then necking, rapid shoulder-placing, equal-diameter growth, pulling-off and cooling are sequentially carried out, so that the lithium niobate crystal is obtained.
Further, the temperature of the seeding operation is 1240-1270 ℃.
Further, in the seeding operation process, the crystal pulling speed is 2-4 mm/h.
Further, the length of the necking is 1-3 cm; the lifting speed in the rapid shoulder putting process is 10-20 mm/h; the lifting speed in the equal diameter growth process is 2-4 mm/h.
Further, the lithium source comprises at least one of lithium carbonate and lithium oxide; the niobium source comprises niobium oxide.
In a second aspect, the present application provides a lithium niobate crystal produced by the method described above.
According to the preparation method of the lithium niobate crystal, provided by the first aspect of the application, the temperature field structure and the growth parameters of the lithium niobate crystal are calculated respectively through simulation, deduction and calculation methods, and the optimal temperature field structure of crystal growth, the growth parameters such as the fastest growth rate allowed by thermodynamics, the pulling growth rate and the like are obtained respectively. And then in the calculated temperature field structure, according to the calculated crystal growth parameters, adopting a pulling method to carry out crystal growth, thereby remarkably improving the growth efficiency of the lithium niobate crystal, and having low preparation energy consumption, short growth process time and high crystal yield. And the prepared lithium niobate crystal has large size, and the problems that the design period of the large-size lithium niobate crystal growth technology is long, the growth parameters need to be optimized repeatedly, the yield is low, the large-size crystal is difficult to prepare and the like are effectively solved.
The lithium niobate crystal provided by the second aspect of the application is prepared by the method, not only has high preparation efficiency, but also has large size of the prepared lithium niobate crystal which can be larger than 6 inches, and meets the application requirements of the rapidly-developed filter market.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following description will briefly introduce the drawings that are needed in the embodiments or the description of the prior art, it is obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a temperature field structure for crystal growth according to an embodiment of the present application;
fig. 2 is a schematic diagram of the external structure of a lithium niobate crystal provided in example 1 of the present application;
FIG. 3 is a schematic view of a thermal insulation structure for crystal growth according to example 1 of the present application;
FIG. 4 is a quasi-static d of the lithium niobate crystal provided in example 1 of the present application 33 Tester for detecting lithium niobate crystal d 33 Position point of piezoelectric constant.
Detailed Description
In order to make the technical problems, technical schemes and beneficial effects to be solved by the present application more clear, the present application is further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the present application.
In this application, the term "and/or" describes an association relationship of an association object, which means that there may be three relationships, for example, a and/or B may mean: a alone, a and B together, and B alone. Wherein A, B may be singular or plural. The character "/" generally indicates that the context-dependent object is an "or" relationship.
In the present application, "at least one" means one or more, and "a plurality" means two or more. "at least one of" or the like means any combination of these items, including any combination of single item(s) or plural items(s). For example, "at least one (individual) of a, b, or c," or "at least one (individual) of a, b, and c" may each represent: a, b, c, a-b (i.e., a and b), a-c, b-c, or a-b-c, wherein a, b, c may be single or multiple, respectively.
It should be understood that, in various embodiments of the present application, the sequence number of each process does not mean that the sequence of execution is sequential, and some or all of the steps may be executed in parallel or sequentially, where the execution sequence of each process should be determined by its functions and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.
The terminology used in the embodiments of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in this application in the examples and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.
The weights of the relevant components mentioned in the embodiments of the present application may refer not only to specific contents of the components, but also to the proportional relationship between the weights of the components, and thus, any ratio of the contents of the relevant components according to the embodiments of the present application may be enlarged or reduced within the scope disclosed in the embodiments of the present application. Specifically, the mass in the specification of the embodiment of the present application may be a mass unit well known in the chemical industry field such as μ g, mg, g, kg.
The terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated for distinguishing between objects such as substances from each other. For example, a first XX may also be referred to as a second XX, and similarly, a second XX may also be referred to as a first XX, without departing from the scope of embodiments of the present application. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature.
An embodiment of the present application provides a method for preparing a lithium niobate crystal, including the following steps:
s10, calculating a temperature field structure of lithium niobate crystal growth;
s20, calculating growth parameters of lithium niobate crystals;
s30, mixing and drying the lithium source and the niobium source to obtain a mixed raw material;
s40, sintering the mixed raw materials in an air atmosphere to obtain a lithium niobate polycrystal block;
s50, melting the lithium niobate polycrystal blocks in the calculated temperature field structure, and performing crystal growth by adopting a pulling method under the guidance of seed crystals according to calculated growth parameters to obtain lithium niobate crystals.
According to the preparation method of the lithium niobate crystal, provided by the first aspect of the embodiment of the application, the temperature field structure and the growth parameters of the lithium niobate crystal are calculated respectively through simulation, deduction and calculation methods, and the optimal temperature field structure of crystal growth, the fastest growth rate allowed by thermodynamics, the pulling growth rate and other growth parameters are obtained respectively. Then in the calculated temperature field structure, according to the calculated crystal growth parameters, the crystal growth is carried out by adopting a pulling method, the growth efficiency of the lithium niobate crystal is obviously improved, the preparation energy consumption is low, the growth process time is short, and the crystal yield is high. And the prepared lithium niobate crystal has large size, and the problems that the design period of the large-size lithium niobate crystal growth technology is long, the growth parameters need to be optimized repeatedly, the yield is low, the large-size crystal is difficult to prepare and the like are effectively solved.
In some embodiments, in the step S10, the step of calculating the temperature field structure of the growth of the lithium niobate crystal includes:
s11, calculating a temperature gradient value in a crystal growth space in the growth process of the lithium niobate crystal;
s12, calculating a temperature field structure of lithium niobate crystal growth according to the temperature gradient value, the thermal conductivity of the heat preservation material and the appearance structure of the heat preservation material.
In some embodiments, in the step S11, the step of calculating the temperature gradient value in the crystal growth space during the growth of the lithium niobate crystal includes:
s111, assuming that a lithium niobate single crystal growth temperature field is a steady-state temperature field (namely, an original point is fixed on a 0 point of a solid/liquid interface in a motion coordinate system), the lithium niobate single crystal growth temperature field has cylindrical symmetry, and according to a heat transfer equation, a temperature expression is shown as a formula (III):
wherein r is,And z is the spatial variable of the crystal, T is the temperature.
The concept of the heat transfer equation is not particularly limited in the embodiment of the present application, and may be a heat transfer equation well known to those skilled in the art, in which the radius of the lithium niobate single crystal isr a The length is l, the density is d, the specific heat is c, and the heat conduction coefficient K is constant.
In some embodiments, according to the heat transfer equationThe heat conduction equation for the crystal in the steady-state temperature field is +.>The above formula (III) can then be obtained using cylindrical coordinates.
Then introducing a temperature function θ (r, z) instead of T (r, z), θ (r, z) =t (r, z) -T 0 Obtaining a relation:
s112, establishing boundary conditions to obtain an axial temperature gradient in the growth space of the lithium niobate crystalAs shown in formula (IV); and radial temperature gradient in the growth space of lithium niobate crystals>As shown in formula (V);
wherein r is a Radius, theta, of lithium niobate crystal m As a function of the equilibrium temperature, h=ε/K, ε is the heat exchange coefficient, ε=ε 0 +ε R ，ε 0 Epsilon for convective heat exchange coefficient R Is the radiant heat exchange coefficient.
In some embodiments, a boundary condition is established:
when z=0, θ=t m -T 0 ；
When z=1, the number of times,
when z=r a In the time-course of which the first and second contact surfaces,
wherein r is a Is the radius of lithium niobate crystal, K is the heat conduction coefficient, T m For equilibrium temperature, ε 0 Epsilon for convective heat exchange coefficient R Is the radiant heat exchange coefficient.
When ε/K is small, we get the differential equation approximation solution (III) that satisfies the boundary conditions:
wherein θm is an equilibrium temperature function, h=ε/K, ε is a heat exchange coefficient, ε=ε0+εR, ε0 is a convection heat exchange coefficient, εR is a radiant heat exchange coefficient.
The components of the temperature gradient vector in the lithium niobate crystal in the axial direction and the radial direction, namely the axial temperature gradient formula (IV) and the radial temperature gradient formula (V) can be derived.
In some embodiments, in the step S12, the step of calculating the temperature field structure of the growth of the lithium niobate crystal includes:
s121, calculating the thickness of the heat preservation layer and the appearance structure of the heat preservation material according to the geometric shape of the target lithium niobate crystal, the lithium property of the lithium niobate crystal and the heat conductivity of the heat preservation material;
s122, counting the melt center of the lithium niobate crystal and melt temperatures at a plurality of different positions away from the melt center according to the temperature gradient value, the thickness of the heat preservation layer and the appearance structure of the heat preservation material, and calculating the radial temperature gradient; and calculating the axial temperature gradient by counting the melt center of the lithium niobate crystal and the environmental temperatures of a plurality of different positions vertically away from the melt center.
According to the temperature gradient value, the lithium content of the lithium niobate crystal and the thermal conductivity of the thermal insulation material, which are obtained through the steps, the thickness of the thermal insulation layer and the appearance structure of the thermal insulation material are calculated; and then calculating an axial temperature gradient and a radial temperature gradient according to the temperature gradient value, the thickness of the heat preservation layer and the appearance structure of the heat preservation material to obtain a temperature field structure of the grown lithium niobate crystal. Specifically, according to the calculated temperature gradient in the three-dimensional space, the three-dimensional space assembly of different heat preservation materials is designed by utilizing the heat conductivity of the different heat preservation materials and combining the geometric structures of the heat preservation materials, and the calculated temperature field structure is met, so that the design and output can be completed.
In some embodiments, the thermal insulation material is selected from at least one of siliceous thermal insulation material, silicate thermal insulation material, corundum thermal insulation material, magnesium calcium thermal insulation material, aluminum magnesium thermal insulation material, magnesium siliceous thermal insulation material, zirconium thermal insulation material. The types and choices of the heat insulating materials are not particularly limited in the embodiments of the present application, and the heat insulating materials can be selected and adjusted according to actual production conditions, raw material conditions and product requirements by those skilled in the art. The heat insulating material in the embodiment of the application is preferably a combination of a plurality of heat insulating materials, and more preferably a plurality of combinations of siliceous heat insulating materials, aluminum silicate heat insulating materials, corundum heat insulating materials, magnesium calcium heat insulating materials, aluminum magnesium heat insulating materials, magnesium siliceous heat insulating materials and zirconium refractory heat insulating materials. As shown in figure 1, the building block type three-dimensional space heat-insulating structure composed of different heat-insulating materials can be designed by utilizing the heat conductivity of the different heat-insulating materials and combining the geometric structures of the heat-insulating materials through various heat-insulating materials such as alumina felt, corundum sand, mullite and the like, so that the design of a temperature field structure is realized.
In some embodiments, in the step S20, the step of calculating the growth parameters of the lithium niobate crystal includes:
s21, according to the rationalization of chemical bonds of crystal growth, calculating the anisotropic relative growth rate of the lithium niobate crystal by referring to a formula (I):
wherein R is uvw Is a lithium niobate crystal edge [ uvw ]]The relative growth rate in the direction, K, is the rate constant,is edge [ uvw]Chemical bonding energy of directional growth, A uvw For growing primitive edges [ uvw]Projected area of direction d uvw Is a lithium niobate crystal edge [ uvw ]]The step height in the direction;
s22, determining the maximum thermodynamic growth rate of different pulling growth directions according to the anisotropic relative growth rate and the lattice energy data of the lithium niobate crystal;
s23, determining the pulling growth direction of the lithium niobate crystal, and obtaining the thermodynamic growth rate of the corresponding growth direction;
s24, calculating the pulling growth rate of the lithium niobate crystal according to the diameter and the length of the lithium niobate crystal which is required to grow.
According to the embodiment of the application, the growth parameters of the lithium niobate crystal are calculated, the chemical bonding structure at the growth interface along the axial direction and the radial direction is determined, and then the corresponding relative growth rate is found out according to the formula (I); then combining the corresponding relative growth rates found in the steps with the lattice energy of the lithium niobate crystal to obtain the growth rates of the lithium niobate crystal in different pulling growth directions; and finally, calculating the pulling growth rate of the lithium niobate crystal according to the isodiametric size and the growth rate of the lithium niobate crystal.
In some embodiments, in the step S21, the definition and selection of each parameter in the formula (I) are not particularly limited, and may be defined in a conventional manner well known to those skilled in the art, which accords with the basic common knowledge of those skilled in the art.
In some embodiments, in the step S22, according to the calculated anisotropic relative growth rate, morphology simulation software is carried in to obtain a thermodynamic growth morphology simulated by the lithium niobate crystal; combined lithium niobate crystal structureThe relative growth rate R of different growth directions is calculated by the formula (I) according to the parameters of bond length, bond angle and the like uvw 。
The concept of the growth rate of the lithium niobate crystal according to the embodiment of the present application is not particularly limited, and may be defined in a conventional manner well known to those skilled in the art, preferably refers to an increase in crystal quality per unit time, and in particular, the crystal growth rate of the lithium niobate crystal more preferably refers to the fastest growth rate allowed by thermodynamics during the growth of the lithium niobate crystal.
The concept of the pull growth rate of the lithium niobate crystal is not particularly limited in the embodiments, and the pull growth rate is preferably defined as a linear rate of a specific size crystal rise per unit time in the pull method according to conventional definitions well known to those skilled in the art, and growth with a large crystal size and a large pull rate results in a high crystal growth rate. The lattice energy in the examples herein refers to the energy expended to break 1 mole of crystals, turning them into completely separated gaseous free ions.
In some embodiments, in the step S23, the anisotropic relative growth rate R obtained according to the step uvw And lattice energy data, determining a maximum thermodynamic growth rate for different pull growth directions; according to the actual growth requirement, the thermodynamic growth rate of the corresponding growth direction can be determined by selecting the seed crystal to grow backwards. In some embodiments, the seed growth may be a thermodynamically optimal pull growth direction.
The direction of the pulling growth of the lithium niobate crystal is not particularly limited, and can be calculated according to the above formula by a person skilled in the art, and can be selected and adjusted according to practical application conditions, raw material conditions and product requirements, and the direction of the pulling growth of the lithium niobate crystal in the embodiment of the present application is preferably [010] or [001 ].
In some embodiments, in the step S24, the step of calculating the pull-up growth rate of the lithium niobate crystal includes:
according to the diameter and length of the lithium niobate crystal to be grown, calculating the pull-up growth rate of the lithium niobate crystal according to the formula (II):
wherein v is the pulling speed, K of the lithium niobate crystal s Thermal conductivity of crystal, dT/dx s Is the temperature gradient of the lithium niobate crystal, K (K) L dT/dx is the thermal conductivity of the melt L Temperature gradient of melt ρ s Is the density of lithium niobate crystals, and L is the latent heat of solidification.
The specific types of the lithium source and the niobium source in the embodiments of the present application are not particularly limited, as long as the corresponding lithium niobate crystal phases can be generated by the reaction. In some embodiments, in step S30, the lithium source includes at least one of lithium carbonate and lithium oxide; the niobium source comprises niobium oxide.
The mixing conditions of the lithium source and the niobium source in the examples are not particularly limited, and those skilled in the art can adjust the mixing conditions according to actual production conditions and raw material conditions, and the mixing time is preferably 20 to 48 hours, more preferably 20 to 30 hours, and even more preferably 20 to 24 hours. The mode of mixing is not particularly limited in the present application, and mixing by a mixer is preferable. In some embodiments, the lithium source and the niobium source are weighed in stoichiometric proportions and mixed in a dry environment for 20 to 24 hours with a blender to obtain a mixed raw material. Further, in order to reduce the volume of the mixed raw material, the mixed raw material is pressed into a cake shape by a press machine after being pressed into a cake shape, and the cake-shaped mixed raw material is obtained.
In some embodiments, in the step S40, the mixed raw materials are sintered in an air atmosphere to obtain a lithium niobate polycrystal block. In some embodiments, the conditions for sintering the mixed feedstock include: sintering treatment is carried out in an air atmosphere with the temperature of 700-1100 ℃. Since gases are generated during sintering, which affect crystal growth, the heat treatment is performed under an air atmosphere in order to ensure removal of moisture and formation of oxides. In addition, in order to ensure formation of a desired lithium niobate phase, the sintering temperature is 700 to 1100 ℃, and a lithium niobate crystal phase cannot be formed at too low a temperature, and the lithium niobate crystal phase may be melted or decomposed at too high a temperature. In some embodiments, the sintering temperature may be 700-800 ℃, 800-900 ℃, 900-1000 ℃, 1000-1100 ℃, etc.
In some embodiments, in the step S50, after the lithium niobate polycrystal lump is melted in the calculated temperature field structure, the crystal growth is performed by using a pulling method under the guidance of the seed crystal according to the calculated growth parameters, so as to obtain the lithium niobate crystal. In some embodiments, the step of performing crystal growth by the Czochralski method comprises: after the lithium niobate polycrystal material block is melted and the characteristic liquid flow line appears, the seed crystal with a specific growth direction is used for carrying out seeding operation according to the calculated growth parameters, and then necking, rapid shoulder-release, equal-diameter growth, pulling-off and cooling are sequentially carried out, so that the lithium niobate crystal is obtained.
In some embodiments, lithium niobate crystals are loaded into a noble metal crucible, the crucible is loaded into a crystal growth furnace, and a thermal insulation material is arranged according to a calculated temperature field structural design; under the air atmosphere, heating up and starting heating equipment to enable the polycrystalline material block to be heated to be higher than the melting point of lithium niobate, when a characteristic liquid flow line appears, the polycrystalline material is molten, then seed crystals with specific growth directions are put down for seeding operation, and lithium niobate crystals are obtained through the processes of necking down, rapid shoulder putting, equal-diameter growth, pulling-out, cooling and the like, and the grown crystals are cylindrical, flat shoulder and flat tail. The growth direction of the used lithium niobate seed crystal is selected according to the calculation result or the actual requirement, and the growth speed is different due to different growth directions.
In some embodiments, the seeding operation is performed at a temperature of 1240 to 1270deg.C, which is for the purpose of melting lithium niobate crystals, when a melt flow line occurs in the crucible or based on an infrared thermometer. In some embodiments, the temperature of the seeding operation may be 1240-1250 ℃, 1250-1260 ℃, 1260-1270 ℃, etc.
In some embodiments, in the seeding operation process, the crystal pulling speed is 2-4 mm/h, so that the growth efficiency of the lithium niobate crystal is effectively improved, the process time is shortened, and the cost is reduced. In some embodiments, the crystal pulling rate may be 2mm/h, 3mm/h, 4mm/h, etc. during the seeding operation.
In some embodiments, the seeding process remotely performs a "seeding" operation by remotely observing the contact and growth/melting of the seed crystal and melt surface through a viewing window. When the seed crystal just contacts the liquid level of the melt, the seed crystal slightly grows, and the growth temperature is proved to be proper; if melting, the growth temperature is proved to be too high, and the growth temperature is regulated down. After seeding, the process enters into necking operation, and the necking length is 1-3 cm. Then, the crystal enters a rapid shouldering stage, and the lifting speed is 10-20 mm/h; and then starting the equal-diameter growth, wherein the lifting speed is 2-4 mm/h, and utilizing a remote observation function to monitor the whole growth process of the lithium niobate crystal in situ.
In a second aspect, embodiments of the present application provide a lithium niobate crystal produced by the method described above.
The lithium niobate crystal provided by the second aspect of the embodiment of the application is prepared by the method, not only has high preparation efficiency, but also has large size of the prepared lithium niobate crystal which can be larger than 6 inches, and meets the application requirements of the rapidly-developed filter market.
The lithium niobate crystal prepared by the embodiment of the application belongs to a trigonal system, and has the melting point of 1250 ℃ which is lower than that of the crystals such as a rare earth orthosilicate scintillation crystal, a rare earth silicate scintillation crystal, a yttrium aluminum garnet scintillation crystal and the like. The different compositions, crystal structures and melting points enable the heating mode, growth rate, growth direction selection and other growth methods of the lithium niobate crystal to be completely different.
In order that the details and operations of the foregoing implementation of the present application may be clearly understood by those skilled in the art, and that the advanced performance of the lithium niobate crystal and the preparation method thereof according to the embodiments of the present application may be significantly reflected, the foregoing technical solutions are exemplified by a plurality of examples.
Example 1
A lithium niobate crystal, the preparation of which comprises the steps of:
(1) [001] direction lithium niobate crystal growth rate calculation:
a) According to formula (I)And lithium niobate crystal data, calculation [001]]The relative growth rate in the direction was 1.2;
b) The growth rate is 20mm/h according to the lattice energy data of the lithium niobate crystal;
c) Setting the diameter of lithium niobate crystal to 105mm, the length to 100mm and the crystal density to 4.6g/cm 3 Melt Density 3.8g/cm 3 The thermal conductivity is 38W/(m.K) @25 ℃, the solidification latent heat is 25.94kJ/mol, the axial temperature gradient is 40K/cm, and the thermal conductive material is represented by the formula (II)The pulling growth rate is 8mm/h;
d) The initial growth rate of the experiment is 8mm/h;
(2) Calculating an insulating layer:
a) The heat-insulating material is selected to be light mullite, and the heat conductivity coefficient is 0.35W/(m.K);
b) According to (IV)And (V)Calculating, wherein the axial temperature gradient is 40K/cm, the radial temperature gradient is 5K/cm, and the heat-insulating layer is designed into a cylindrical light mullite heat-insulating structure with the thickness of 50 mm; wherein, the schematic diagram of the heat preservation structure is shown in figure 3;
(3) Preparing a polycrystalline raw material:
a) Weighing: accurately weighing lithium carbonate and niobium oxide raw materials with the molar ratio of 48.6:51.4;
b) Mixing: mixing the weighed raw materials in a mixing machine for 24 hours, keeping the external environment dry and keeping the humidity less than 20%;
c) Pressing: pressing the mixed raw materials into cakes through a press and a grinding tool;
d) Firing: presintering the cake-shaped raw material for 10 hours at 850 ℃ under the air condition to obtain a polycrystalline raw material;
(4) Growth of crystal by Czochralski method:
a) Putting the polycrystalline raw material into a platinum crucible with the diameter of 150mm in a temperature field, building an insulating layer, and selecting a lithium niobate seed crystal in the [001] direction;
b) Seeding: when the seed crystal just contacts the liquid level of the melt, the seed crystal grows slightly, which indicates that the seeding temperature is proper, seeding is started, and the pulling speed is adjusted to 8mm/h;
c) Necking and shouldering: the pulling speed is regulated to 6mm/h, after the necking length is 1-3cm, the crystal enters a shouldering stage, and the pulling speed is 2mm/h;
d) Shoulder harvesting and constant diameter growth: the lifting speed is 3.0mm/h;
e) Pulling out and cooling: pulling the crystal after the crystal grows to a set length, and cooling for 12 hours to obtain the multi-domain lithium niobate crystal. The outline of the grown lithium niobate crystal is shown in figure 2, and the crystal has no ending and flat shoulder.
Further, in order to verify the progress of example 1 of the present application, the diameter of the grown [001] direction lithium niobate crystal was measured to be 102.+ -. 0.5mm according to YS/T554-2007 standard; the preparation of large-size lithium niobate crystals is realized by the embodiment of the application.
Visual inspection of crack-free under laser beam irradiation and light macroscopic quality defects such as bubbles, cloud layers and the like; the lithium niobate crystal prepared by the embodiment of the application has few defects and high quality.
In addition, quasi-static d is adopted 33 The tester detects 9 points in the lithium niobate crystal, wherein the lithium niobate crystal d 33 The detected position point of the piezoelectric constant is shown in FIG. 4, d 33 The piezoelectric values are shown in table 1 below. By lithium niobate crystal d 33 As can be seen from the detection of the piezoelectric constant, the lithium niobate crystal prepared by the embodiment of the application has uniform quality and high quality.
TABLE 1
| Position of | d 33 Value (pC/N) |
| 1 | 12.0 |
| 2 | 19.1 |
| 3 | 11.2 |
| 4 | 15.1 |
| 5 | 11.6 |
| 6 | 17.5 |
| 7 | 16.3 |
| 8 | 14.4 |
| 9 | 18.2 |
According to the test results, the preparation method of the lithium niobate crystal of the embodiment of the application calculates the temperature field structure and the growth parameters of the lithium niobate crystal respectively through simulation, deduction and calculation methods, and then performs crystal growth according to the calculated crystal growth parameters in the calculated temperature field structure by adopting a pulling method, so that the growth efficiency of the lithium niobate crystal is remarkably improved, the preparation energy consumption is low, and the growth process time is short; and the preparation of large-size lithium niobate crystal is realized, the crystal yield is high, the crystal defects are few, and the quality is high. Can meet the application requirements of the rapidly-developed filter market.
The foregoing description of the preferred embodiments of the present application is not intended to be limiting, but is intended to cover any and all modifications, equivalents, and alternatives falling within the spirit and principles of the present application.
Claims (6)
1. A method for preparing lithium niobate crystal, characterized by comprising the following steps:
calculating a temperature field structure of lithium niobate crystal growth;
calculating the growth parameters of lithium niobate crystals;
mixing and drying a lithium source and a niobium source to obtain a mixed raw material; wherein, the mixing time is 20-48 h;
sintering the mixed raw materials in an air atmosphere to obtain a lithium niobate polycrystal block;
in the calculated temperature field structure, after the lithium niobate polycrystal block is melted, under the guidance of seed crystal, crystal growth is carried out by adopting a pulling method according to the calculated growth parameters, and then lithium niobate crystal is obtained;
the conditions for sintering the mixed raw materials include: sintering at 700-1100 deg.c in air atmosphere;
the crystal growth step by the pulling method comprises the following steps: after the lithium niobate polycrystal block is melted and a characteristic liquid flow line appears, carrying out seeding operation by using the seed crystal with a specific growth direction according to the calculated growth parameters, and then sequentially carrying out necking, rapid shouldering, constant diameter growth, pulling-off and cooling to obtain the lithium niobate crystal; the temperature of the seeding operation is 1240-1270 ℃, the pulling speed of a crystal is 8mm/h in the seeding operation process, the pulling speed in the necking process is 6mm/h, after the length of the necking is 1-3cm, the crystal enters a shouldering stage, the pulling speed in the rapid shouldering process is 2mm/h, the pulling speed in the constant diameter growth process is 2-4 mm/h, the lithium source comprises lithium carbonate, the niobium source comprises niobium oxide, and the molar ratio of the lithium carbonate to the niobium oxide is 48.6:51.4;
the step of calculating the growth parameters of the lithium niobate crystal comprises the following steps:
according to the rationale of chemical bonds for crystal growth, the anisotropic relative growth rate of lithium niobate crystals is calculated with reference to formula (I):
wherein R is uvw Is a lithium niobate crystal edge [ uvw ]]The relative growth rate in the direction, K, is the rate constant,is edge [ uvw]Chemical bonding energy of directional growth, A uvw For growing primitive edges [ uvw]Projected area of direction d uvw Is a lithium niobate crystal edge [ uvw ]]The step height in the direction;
determining the maximum thermodynamic growth rate of different pulling growth directions according to the anisotropic relative growth rate and lattice energy data of the lithium niobate crystal;
determining the pulling growth direction of the lithium niobate crystal, and obtaining the thermodynamic growth rate of the corresponding growth direction;
calculating the pulling growth rate of the lithium niobate crystal according to the diameter and the length of the lithium niobate crystal to be grown;
the step of calculating the pull-up growth rate of the lithium niobate crystal includes:
calculating the pull-up growth rate of the lithium niobate crystal according to the diameter and length of the lithium niobate crystal required to be grown and with reference to the formula (II):
wherein v is the pulling speed, K of the lithium niobate crystal s Thermal conductivity of crystal, dT/dx s Is the temperature gradient, K, of lithium niobate crystal L dT/dx is the thermal conductivity of the melt L Temperature gradient of melt ρ s Is the density of lithium niobate crystals, and L is the latent heat of solidification.
2. The method of preparing a lithium niobate crystal according to claim 1, wherein the step of calculating a temperature field structure of the growth of the lithium niobate crystal comprises:
calculating a temperature gradient value in a crystal growth space in the growth process of the lithium niobate crystal;
and calculating the temperature field structure of the lithium niobate crystal according to the temperature gradient value, the thermal conductivity of the heat preservation material and the appearance structure of the heat preservation material.
3. The method for producing a lithium niobate crystal according to claim 2, wherein the step of calculating a temperature gradient value in a crystal growth space during the growth of the lithium niobate crystal comprises:
assuming that the growth temperature field of the lithium niobate single crystal is a steady-state temperature field and has cylindrical symmetry, according to a heat transfer equation, the temperature expression is as shown in formula (III):
wherein r is,And z is the spatial variable of the crystal, T is the temperature;
establishing boundary conditions to obtain axial temperature gradient in the growth space of lithium niobate crystalAs shown in formula (IV); and radial temperature gradient in the growth space of lithium niobate crystals>As shown in formula (V);
wherein r is a Radius, theta, of lithium niobate crystal m As a function of the equilibrium temperature, h=ε/K, ε is the heat exchange coefficient, ε=ε 0 +ε R ，ε 0 Epsilon for convective heat exchange coefficient R Is the radiant heat exchange coefficient.
4. A method of preparing a lithium niobate crystal according to claim 3, wherein the step of calculating the temperature field structure of the growth of the lithium niobate crystal comprises:
calculating the thickness of the heat preservation layer and the appearance structure of the heat preservation material according to the geometric shape of the target lithium niobate crystal, the physical property of the lithium niobate crystal and the heat conductivity of the heat preservation material;
counting the melt center of the lithium niobate crystal and melt temperatures at a plurality of different positions away from the melt center according to the temperature gradient value, the thickness of the heat preservation layer and the appearance structure of the heat preservation material, and calculating radial temperature gradients; and calculating the axial temperature gradient by counting the melt center of the lithium niobate crystal and the environmental temperatures of a plurality of different positions vertically away from the melt center.
5. The method for preparing lithium niobate crystal according to claim 4, wherein the thermal insulation material is at least one selected from siliceous thermal insulation material, silicate thermal insulation material, corundum thermal insulation material, magnesium calcium thermal insulation material, aluminum magnesium thermal insulation material, magnesium siliceous thermal insulation material, zirconium thermal insulation material.
6. A lithium niobate crystal, characterized in that the lithium niobate crystal is produced by the method according to any one of claims 1 to 5.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111022496.9A CN113913937B (en) | 2021-09-01 | 2021-09-01 | Lithium niobate crystal and preparation method thereof |
| PCT/CN2021/137616 WO2023029288A1 (en) | 2021-09-01 | 2021-12-13 | Lithium niobate crystal and preparation method therefor |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111022496.9A CN113913937B (en) | 2021-09-01 | 2021-09-01 | Lithium niobate crystal and preparation method thereof |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN113913937A CN113913937A (en) | 2022-01-11 |
| CN113913937B true CN113913937B (en) | 2023-07-18 |
Family
ID=79233768
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202111022496.9A Active CN113913937B (en) | 2021-09-01 | 2021-09-01 | Lithium niobate crystal and preparation method thereof |
Country Status (2)
| Country | Link |
|---|---|
| CN (1) | CN113913937B (en) |
| WO (1) | WO2023029288A1 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116200828B (en) * | 2023-05-06 | 2023-07-07 | 天通控股股份有限公司 | Preparation method of large-size lithium niobate crystal |
| CN116905087B (en) * | 2023-09-13 | 2023-11-28 | 天通控股股份有限公司 | Growth method of lithium tantalate crystal |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2003002782A (en) * | 2001-06-15 | 2003-01-08 | Toshiba Ceramics Co Ltd | Method and device for pulling silicon single crystal |
| CN105019024B (en) * | 2015-07-09 | 2018-02-06 | 山东大学 | A kind of method that lithium niobate crysal near stoichiometric ratio is grown using the adjustable thermal field device of thermograde |
| CN106757354A (en) * | 2017-01-24 | 2017-05-31 | 中国科学院长春应用化学研究所 | The growth of low-cost rare earth scintillation crystal |
| CN107488874A (en) * | 2017-09-04 | 2017-12-19 | 中国科学院长春应用化学研究所 | A kind of design method of temperature field structure for rare earth crystal growth technique and the growth technique of low-cost rare earth crystal |
| CN107740188A (en) * | 2017-09-04 | 2018-02-27 | 中国科学院长春应用化学研究所 | The computational methods and computing system of pulling growth speed in the growth technique of low-cost rare earth crystal |
| JP7310339B2 (en) * | 2019-03-12 | 2023-07-19 | 住友金属鉱山株式会社 | Method for growing lithium niobate single crystal |
| CN111206282A (en) * | 2019-10-30 | 2020-05-29 | 德清晶辉光电科技股份有限公司 | Production method of 8-inch lithium niobate crystal |
-
2021
- 2021-09-01 CN CN202111022496.9A patent/CN113913937B/en active Active
- 2021-12-13 WO PCT/CN2021/137616 patent/WO2023029288A1/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| WO2023029288A1 (en) | 2023-03-09 |
| CN113913937A (en) | 2022-01-11 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN113913937B (en) | Lithium niobate crystal and preparation method thereof | |
| TWI482737B (en) | Polycrystalline silicon rod and process for production thereof | |
| CN1763264A (en) | Flux method for growth of gallium phosphate crystal | |
| JP5774400B2 (en) | Method for evaluating silica powder, silica glass crucible, method for producing silica glass crucible | |
| Halliyal et al. | Study of the piezoelectric properties of Ba 2 Ge 2 TiO 8 glass-ceramic and single crystals | |
| CN104357906A (en) | Multi-crucible three-dimensional sapphire single crystal growing device | |
| CN104695018A (en) | Aluminum gallium tantalum calcium silicate piezoelectric crystal and preparing method thereof | |
| Nakao et al. | Growth and SAW properties of rare-earth calcium oxoborate crystals | |
| CN104250852A (en) | Sapphire crystal growth device and growth method | |
| CN111206282A (en) | Production method of 8-inch lithium niobate crystal | |
| CN110079861A (en) | Yttrium phosphate strontium crystal and the preparation method and application thereof | |
| CN104264213A (en) | EFG (edge-defined film-fed growth) device of large-size doped sapphire crystals and growth process thereof | |
| JPS59207900A (en) | Method of growing large single crystals from many seed crystals | |
| CN108301041A (en) | A kind of crucible used for polycrystalline silicon ingot casting and preparation method thereof | |
| CN110318097B (en) | Preparation method of lanthanum gallium niobate single crystal | |
| CN107488874A (en) | A kind of design method of temperature field structure for rare earth crystal growth technique and the growth technique of low-cost rare earth crystal | |
| CN204874816U (en) | Inclined to one side M of growth C is to bubble of sapphire single crystal single crystal growing furnace structure of thinking of a way | |
| CN104178802B (en) | Ternary relaxation ferroelectric piezoelectric crystal and multi-temperature-zone growth method thereof | |
| CN106480502A (en) | A kind of melilite structure high-temperature piezoelectric crystal and preparation method thereof | |
| CN101792928B (en) | High temperature piezocrystal of melilite structure and preparation method and application thereof | |
| CN203049085U (en) | Graphite crucible for growing thermal monocrystal field by utilizing direct-drawing method | |
| CN207775389U (en) | Ingot furnace | |
| JP4353262B2 (en) | Surface acoustic wave device and substrate for piezoelectric device | |
| JP5992572B2 (en) | Method for evaluating silica powder, silica glass crucible, method for producing silica glass crucible | |
| CN110685006A (en) | Intermediate infrared nonlinear optical crystal POC and preparation method thereof |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |