LU501074B1 - Method for processing single crystal substrate element of potassium tantalum-niobate - Google Patents

Abstract

The present invention provides a processing method of customizable high-precision potassium tantalate niobate single crystal substrate element, and belongs to the field of processing of artificial crystals and glass materials, the methods mainly comprises the steps of orienting, cutting, composing, grinding, polishing and unloading the KTN series crystals. The present invention provides a complete solution for the manufacture of KTN single crystal substrate elements, which can be used as electro-optical modulation elements such as optical waveguides, optical switches, and deflectors, as well as sample bases for substrate materials.

Description

METHOD FOR PROCESSING SINGLE CRYSTAL SUBSTRATE HUS0T074 ELEMENT OF POTASSIUM TANTALUM-NIOBATE

TECHNICAL FIELD The present invention relates to a method for processing an artificial crystalline material for electro-optical modulation, and belongs to the field of laser components.

BACKGROUND Electro-optical crystal material is one of the basic materials for all-solid-state laser, which can realize the modulation of laser propagation characteristics.

Electro-optical modulation has the advantages of high efficiency, good stability, fast response and no inertia. Electro-optic crystal is a kind of functional crystal with important applications. The development of high-efficiency electro-optic crystal is of great significance to the development and application of all-solid-state laser technology.

Potassium tantalum niobate (KTa1-«Nb,O03, KTN) crystal is a solid solution mixed crystal of potassium tantalate (KTaO;, KT) and potassium niobate (KNbOs, KN), which has excellent electro-optic properties and photorefractive properties. KTN crystal has a wide application prospect in the fields of beam deflector, Q switch, high-speed optical shutter, holographic storage, optical intensity modulator, optical phase modulator and so on. At the same time, KTN is also widely used as an excellent thin film material and substrate material.

Devices such as optical switches, optical shutters, and deflectors for laser modulation have extremely high requirements for crystal orientation deviation, lattice integrity, and surface flatness of the modulation core components. In order to obtain high quality laser modulator, KTN crystal substrate is required to have no orientation deviation, complete surface lattice and smooth surface without damage. Even the smallest angle deviation or crystal plane defect will destroy the modulation efficiency and performance of laser, and even lead to the change of crystal structure, which will affect the modulation accuracy and stability of components. KTN crystals are typical HUS0T074 hard and brittle materials, and KTN crystals with high niobium content have mechanical properties such as cleavage and anisotropy. KTN crystal is a typical secondary electro-optic crystal material. It is generally > believed that the higher the order of nonlinear modulation, the smaller its nonlinear coefficient. Therefore, the focus of electro-optic modulation research has been limited to linear electro-optic materials and devices for a long time. Lithium niobate (LN), lithium tantalate (LT), rubidium titanyl phosphate (RTP) and lanthanum gallium silicate (LGS) are commonly used, and the corresponding modulation components are all aimed at these linear electro-optic crystals. In addition, due to the infinite solid melt characteristics of KTN crystal, it is very difficult to grow high-quality and large-size single crystal, which limits its research and application. In recent years, with the continuous progress of crystal preparation technology, people have successfully obtained inch-grade and high-quality KTN single crystals that meet the 15° practical requirements, which makes the research and application of KTN more and more attention. The research shows that KTN crystal has even better performance in laser modulation than linear electro-optic crystal. Compared with the traditional acousto-optic mechanical modulation or the existing linear electro-optic modulation the electro-optic modulation based on Kerr effect of KTN crystal is obviously superior to the former in many aspects such as transmission band modulation efficiency and response time. Therefore, the electro-optic modulation based on the secondary electro-optic effect of KTN crystal has more advantages in reducing the driving voltage and device size, and can better meet the needs of the future development of wide-band, miniaturization and integration of lasers.

At present, KTN crystal electro-optic modulation devices have changed from laboratory research to industrial application, the processing and preparation of its components is very important to the performance of crystal devices, However, the existing processing and preparation technologies of laser modulation elements are mostly aimed at linear electro-optic crystal materials, at the same time, the practical application of an electro-optic crystal material is closely related to the unique physical and chemical properties of the crystal, therefore, according to the characteristics of HUS0T074 secondary electro-optic effect and crystallographic characteristics of KTN crystal, the present invention has developed a special processing and preparation technology of KTN electro-optic modulator, which can not only greatly promote the application and popularization of KTN electro-optic modulator, but also have extensive reference significance for secondary electro-optic modulation technology.

SUMMARY According to the characteristics of secondary electro-optic effect and crystallographic characteristics of KTN crystal, the present invention aims to provide 3 processing method of substrate elements applied to KTN series crystal secondary electro-optic modulator devices with different composition ratios and different crystal phases, and provide an element preparation scheme for inventing high-efficiency KTN secondary electro-optic modulator. The technical proposal of the present invention is as follows: a method for processing single crystal substrate element of potassium tantalum niobate, wherein the KTN crystal is KTa1-<NbxO; or M: KTa1Nbx0; crystal with Nb component 0 <x <1, cubic (m3m), tetragonal (4mm) or orthogonal (mm2) crystal phase and doping ions of Cu, Fe, Sn, Ti, Li, Na and Mn single doped or mixed multi-doped. The steps of the method mainly include orientation, cutting, composing, grinding, polishing and dismounting of KTN crystals, specifically as follows: (1) orientation: orienting the KTN crystal comprises orienting the single crystal crystallization planes and the internal growth striation according to the crystallization and growth characteristics of the KTN crystal, and realizing the coincidence of the crystal plane and the geometric plane within a certain error through cutting and 23 grinding trimming. The orientation relationship between the growth striation and the geometric surface is marked.

(2) cutting: taking the directional plane of the crystal as a reference, using a cutting tool to cut a crystal sheet with a designed crystal direction and size according to the diversified application requirements of the KTN crystal in terms of the light passage direction, wherein the cutting size error is less than 10 um and the crystal direction error is less than 0.5°; 17501078 (3) formula: selecting glass or crystal with hardness and elastic modulus similar to that of the processed KTN crystal as a fixture material, designing the shape and size of the fixture according to the geometric size of the crystal processing surface, and manufacturing the fixture by cutting and shaping; selecting paraffin or 502 adhesive to combine the crystal and the fixture into a processing square block according to the application requirement and the Curie temperature value of the crystal sheet. (4) grinding: under the environment of 20-25 °C and humidity of 30-70%, according to the hardness characteristic of KTN crystal, the square block is shaped by using an abrasive, and rough grinding, fine grinding and further fine grinding are carried out, wherein the roughness RMS of the sample after fine grinding is within 150 um, and the thickness uniformity is less than or equal to 2 um; the abrasive of shaping, coarse grinding or fine grinding is selected from carborundum, boron carbide and aluminum oxide; (5) polishing: under the environment of 22+2 °C and humidity of 30-70%, according to the mechanic-chemical properties of KTN crystal, the crystal after fine grinding is roughly polished and finely polished by using a water-based polishing solution and a polishing pad with the abrasive grain size less than 1 um, the surface after fine polishing can be non-damaged, the surface shape is better than A/8, the root mean square roughness (RMS) is less than 1 nm, and the parallelism of the upper surface and the lower surface is within 5"; the abrasive of the water-based polishing solution is selected from diamond, cerium oxide and silicon dioxide; the polishing pad is selected from polyurethane polishing pad, non-woven fabric polishing pad, flannelette polishing pad and asphalt polishing pad.

(6) coating protective film and unloading plate: cleaning the processed surface after fine polishing with acetone and alcohol in sequence in an ultra-clean workbench by using dust-free cloth, self-leveling or spin-coating a layer of alcohol solution of shellac chips as protective paint, wherein the concentration of the alcohol solution of shellac chips is Swt %-20wt%, standing for 30 min, drying in the air, heating to 60-70 °C by using a baking lamp to melt paraffin, and unloading. For processing blocks using

502 adhesive, soak them in acetone solution for 5-12 h after cleaning, and remove the 507074 fixture after 502 adhesive dissolves.

The orientation of crystallization plane in step (1) of the method described in the present invention is accomplished using an X-ray orientation instrument with an error 5 <5' The orientation of internal growth striations was observed by using a magnifier or microscope in backlight on the light-passing surface.

The growth striations of KTN were parallel linear fringes with the same direction generally, and their directions were affected by the crystallization plane direction, but there was no fixed angle relationship between them.

Therefore, according to the growth characteristics and application purposes of KTN single crystals with different compositions, only by carrying out crystal plane orientation and growth striation orientation on single crystal blanks can the unique properties of the growth striation be fully circumvented and utilized to realize the diversified applications of KTN crystals.

In step (2) of the method described in the present invention, the cutting tool can be a diamond saw or dicing blade or wire cutting machine, and the linear speed and feed speed are selected according to the unique hardness and brittleness performance of KTN crystals with different compositions, wherein, the linear speed of the blade or cutting wire is 1000-1500 cm/s, and the cutting feed speed is 4-8 mm/min.

For pure KTa1xNbxO3 crystals with Nb component content x < 0.5, the preferred linear speed of the blade or cutting wire is 1500 cm/s and the feed rate is 5 mm/min, and the cutting parameters can be adjusted appropriately as the composition changes or the doping of different ions causes changes in crystal hardness.

In step (3) of the method described by the present invention, the Mohs hardness of KTN crystal material is 6-7, and when the demand of crystal plane processing surface shape is lower than W12, K9 glass is preferably used as fixture material in consideration of processing and manufacturing cost.

When the processing surface shape requirement of 4/12 or more, KTN crystal material is preferred as the fixture material, and further KTN crystal of the same composition as the sample being processed is preferred as the fixture material.

The shape of the processing surface of the processing square block is similar to the shape of the processing surface of the crystal sheet, and in case of inconsistency, a square is preferred. The dimensions of HUS0T074 the processing square block satisfy an area ratio of 1:50-1:2, preferably 1:15-1:5, between the processing surface of crystal sheet and the processing surface of fixture. The selection of the adhesive is based on the Curie temperature point of the processed KTN crystal and the precision requirement of the desired processed surface. The Curie temperature of KTN crystal can vary from minus tens of degrees to hundreds of degrees above zero with the change of tantalum-niobium ratio, and the cubic phase and tetragonal phase transition will occur above or below the Curie temperature of KTN crystal. Due to the influence of various inevitable microstructure defects in the crystal, the phase transition will inevitably affect the surface accuracy of the crystal machined surface. Therefore, for the selection of adhesives in the present invention, when the surface shape requirement is lower than A/12, the yellow glue which is convenient and time-saving is used as the adhesive, when the surface shape is required to be above A/12, 502 is used as adhesive.

Steps (4) and (5) of the method described by the present invention can be realized manually or by machine. The diversity of the properties and applications of KTN crystals is realized since the tunability of its composition and properties. The processing method steps described in the present invention can be selected from a manual method that is easy to design flexibly or a machine processing method that is consistent in size and efficient in processing according to the processing needs of the KTN crystals, which have a variety of applications, processing shapes and sizes.

In step (4) of the method described in the present invention, according to the grinding mechanism of KTN crystal material with different abrasive materials, diamond is preferred for fast shaping and rough grinding. Aluminum oxide abrasives are preferred for fine and fine grinding to reduce the damage and scratches left by the abrasive on the crystal processing surface and to facilitate subsequent fast, high-quality polishing.

In step (5) of the method described in the present invention, according to the hardness of KTN crystals, polyurethane polishing pads are preferred for rough polishing and asphalt polishing pads are preferred for fine polishing, which can achieve fast and high quality polishing results. 507074 In step (5) of the method described in the present invention, a self-prepared highly efficient dispersed acidic water-based WO.8 cerium oxide polishing solution is used for rough polishing, which comprises: 0.5 wt%-5wt% WO0.8 cerium oxide micropowder, 55 wt%-70wt% deionized water, 0.2 wt%-15wt% KMnO4, 3wt%-10wt% ethylene glycol, 0.1 wt%-1wt% potassium nitrate, 0-1wt% nitric acid, 0-1wt% potassium hydroxide and 0.1 wt%-2wt% polyacrylic acid (PAA). Fine polishing is preferably a suspension mixture of the above-mentioned WO.8 cerium oxide polishing solution and colloidal silica (average particle size of 80nm, concentration of 25 wt%), the volume ratio of the two is preferably 1:1, and the pH value of the above-mentioned polishing solution is 5-10, preferably 5-7. The self-prepared highly efficient dispersed acidic water-based WO0.8 cerium oxide polishing solution is formulated for the hardness, plasticity, and chemical stability of KTN series crystals, which has good dispersion, can quickly achieve chemical mechanical polishing of KTN series crystals, and better polishing quality. In fine polishing, combined with the characteristics of asphalt polishing discs, the present invention uses a suspension mixture of W0.8 cerium oxide polishing solution and colloidal silica (average particle size of 80 nm, concentration of 25 wt%) suspension, which can reasonably adjust the form of friction between the processed crystal surface and the polishing disc, and is conducive to the realization of the synergistic polishing effect of small particles of hard silica and relatively large particles of W0.8 cerium oxide, which can improve the KTN crystal polishing removal rate and surface polishing quality.

The processed KTN crystal substrate in the present invention is crystal substrate of (100), (110) and (111) crystal orientation with crystal orientation error within +-5 ', and the crystal substrate can be shaped as cylinder, cuboid, triangular column, hexagonal column and irregular shape.

The processing and manufacturing method of KTN single crystal substrate element described by the present invention has the following advantages: based on the characteristics that the crystal phase of KTN series crystals 1s closely related to crystal components and ambient temperature, the method carries out accurate directional processing according to the crystallographic characteristics of KTN crystals with HUS0T074 different components and different ion doping at room temperature; the corresponding orientation, cutting, grinding and polishing processes and the coordinated use of corresponding fixture materials, abrasives and polishing solutions can ensure the > accurate crystal orientation and smooth surface of KTN substrate elements, meet the manufacturing requirements of laser modulation devices, and have high processing efficiency and low cost; KTN single crystal substrate prepared by the present invention can not only meet the needs of traditional linear electro-optic modulation devices, but also provide reference for the design and fabrication of secondary electro-optic modulation devices.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING Fig. 1 is a schematic diagram of processing KTN single crystal substrates with different crystal orientations and different shapes according to Example 1 of the present invention; Fig. 2 is a schematic diagram of processing KTN single crystal substrates with different crystal orientations and different shapes according to Example 2 of the present invention; Fig. 3 is a schematic diagram of processing KTN single crystal substrates with different crystal orientations and different shapes according to Example 3 of the present invention; Fig. 4 is a schematic diagram of processing KTN single crystal substrates with different crystal orientations and different shapes according to Example 4 of the present invention.

DETAILED DESCRIPTION The present invention is further explained below in conjunction with the accompanying drawings and embodiments: Example 1 Processing of a high-precision cubic KTN single crystal substrate element, wherein the KTN crystal component is K Tao. sNbo. 503 and the crystal phase is cubic (M3M). The KTN crystal is processed by directional fine polishing on three crystal planes (100), (010) and (001) to process a cube with a target size of 5mm x

Smm x Smm, and the processing steps are as follows: HUS0T074 (1) Orientation: the orientation of KTN blanks was completed by DX-2 X-ray orientator (Dandong Xindongfang Crystal Instrument Co.

Ltd.), and the growth striations of crystal were determined by magnifier and optical microscope.

Two physical planes of crystal blank were trimmed into (100) crystal plane, which were parallel and perpendicular to the growth striations respectively, and the orientation error of crystal plane was less than or equal to 5". (2) Cutting: based on the two directional planes in step (1), the cube crystal sample block with length, width and height of 5.5 mm x 5.5 mm x 5.5 mm is cut by using diamond inner circle cutting machine, the cutting size error is less than 10 y m, the crystal orientation of the cutting plane is (100), (010) and (001) respectively, and the crystal orientation error is less than 0.5. (3) Formula: K9 glass is selected as fixture material, and four fixture blocks of 6 mm x 11 mm x 5.1 mm are cut by inner circle cutting machine, and the verticality of each face of fixture block is shaped.

Paraffin wax was used to combine the crystal sample and fixture to form a processing square, and the overall dimension of the square was about 17 mm x 17 mm x 5.1 mm. (4) Grinding: under the environment of 20-25°C and humidity of 30-70%, the square block is reshape and chamfered by use carborundum to obtain regular processing squares with flat surfaces, mutually perpendicular adjacent surface and chamfered surfaces, and the processing surfaces (exposed surfaces of KTN crystals) of the square blocks are subjected to rough grinding, fine grinding and further fine grinding respectively by using carborundum of W40, W14 and W7, wherein the thickness of each processing surface was removed by rough grinding to be 100 um, the thickness of each processing surface is removed by fine grinding to be 80 um, and the thickness of each processing surface is removed by further fine grinding to be 50 um, after further fine grinding, the surface roughness RMS was within 150 um, and the thickness uniformity was less than or equal to 2 um. (5) Polishing: under the environment of 22+2°C and humidity of 30-70%, the polishing solution (pH=5) prepared with W0.8 cerium oxide micropowder and polyurethane polishing pad are used to roughly polish the polished sample, and the HUS0T074 thickness of each surface removed is about 10 u m, and the sand holes and deep scratches on the working surface were basically removed, and the parallelism between the upper and lower surfaces was 20 ". Then, using the suspension mixture of WO0.8 > cerium oxide polishing solution and colloidal silica as polishing solution, asphalt as polishing disk material, the square block was finely polished. The thickness of each surface removed was less than 10 um, and the surface shape was A/8 after finely polishing. The root mean square roughness RMS was 0.89 nm, and the parallelism between upper and lower surfaces was less than S ".

10 (6) unloading plate and processing of other four surfaces: cleaning the processed surface after the fine polishing in the step (5) with acetone and alcohol in sequence in an ultra-clean workbench, uniformly spin-coating a layer of shellac chips as protective paint, standing for 30min, drying in the air, and heating by using a baking lamp to remove fixture. Then two rounds of steps (3)-(6) were performed on the remaining four unpolished surfaces to obtain six-sided polished KTN crystals with crystal orientations of (100), (010) and (001) on each surface, with crystal orientation error less than 5’, no damage to the surface, root mean square roughness RMS <1 nm and parallelism of the upper and lower surfaces <5". The schematic diagram of the shape and crystal orientation of the processed KTN sample block is shown in Fig. 1.

In example 1, the grinding process of step (4) and the polishing process of step (5) are both manually operated, so that the processing goal can be realized quickly and accurately.

Example 2 Processing of a high-precision Cu ion doped tetragonal KTN single crystal substrate element, wherein the KTN crystal component is Cu: KTao. sNpo 503, and the crystal phase is tetragonal (4mm). (100) crystal plane directional fine polishing was carried out and the target shape is a cylindrical sample with 5 mm (diameter) x 5 mm (height). The processing steps differ from those described in example 1 in that: after cutting out a crystal sample block with a length, width and height of 5.5 mm x 5.5 mm x 5.5 mm in step (2), the four sides perpendicular to the (100) surface are ground into a cylindrical surface using a circular grinding machine to obtain a cylindrical block, and a cylindrical crystal block with a diameter of 5 mm 17501078 and a height of 5.5 mm was obtained.

The processing operation 1s carried out by using a square fixture with the same material and size as that of example 1, and finally a cylindrical Cu: KTaosNbosO3 crystal substrate element as shown in Fig. 2 was obtained.

Its upper and lower circular surface is (100) fine polished surface, no damage to the surface, crystal orientation error less than 5’, root mean square roughness RMS <1 nm, parallelism of upper and lower surface <5". Example 3 Processing of a high-precision cubic KTN single crystal substrate element, wherein the KTN crystal component is K Tao. sNbo. 503 and the crystal phase is cubic (M3M). The (100), (010), (001), (110) crystal planes were polished to obtain an isosceles right angle tripartite columnar sample with a target shape of 5 mm x 5 mm x 5 mm.

The processing steps were as follows: (1) Orientation: the orientation of KTN blanks was completed by DX-2 X-ray orientator (Dandong Xindongfang Crystal Instrument Co.

Ltd.), and the growth striations of crystal were determined by magnifier and optical microscope.

Two physical planes of crystal blank were trimmed into (100) crystal plane, which were parallel and perpendicular to the growth striations respectively, and the orientation error of crystal plane was less than or equal to 5". (2) Cutting: based on the two directional planes in step (1), the cube crystal sample block with length, width and height of 5.5 mm x 5.5 mm x 5.5 mm is cut by using diamond inner circle cutting machine, the cutting size error is less than 10 u m, the crystal orientation of the cutting plane 1s (100), (010) and (001) respectively, and the crystal orientation error is less than 0.5. Then, the (110) plane was cut along the diagonal direction of the (100) plane, and the (110) plane was ground and trimmed with an error of less than 10° to obtain two directionally trimmed tripartite columnar samples. (3) Formula: K9 glass is selected as fixture material, and four fixture blocks of 6 mm x 11 mm x 5.1 mm are cut by inner circle cutting machine, and the verticality of each face of fixture block is shaped.

Paraffin wax was used to combine the two crystal samples and fixture to form a processing square, and the overall dimension of the square was about 17 mm x 17 mm x 5.1 mm. When processing (110) crystal plane, 507074 single-side processing is adopted and two K9 glass blocks of 7 mm x 17 mm x 5.1 mm and 7mm x 14mm x 5.1 mm were used as fixture, and the size of the processing square is 21 mm x 24 mm x 5.1 mm.

(4) Grinding: under the environment of 20-25°C and humidity of 30-70%, the square block is reshape and chamfered by use carborundum to obtain regular processing squares with flat surfaces, mutually perpendicular adjacent surface and chamfered surfaces, and the processing surfaces (exposed surfaces of KTN crystals) of the square blocks are subjected to rough grinding, fine grinding and further fine grinding respectively by using carborundum of W40, W14 and W7, wherein the thickness of each processing surface is removed by rough grinding to be 100 um, the thickness of each processing surface is removed by fine grinding to be 80 um, and the thickness of each processing surface is removed by further fine grinding to be 50 um, after further fine grinding, the surface roughness RMS is within 150 um, and the 15° thickness uniformity is less than or equal to 2 um.

(5) Polishing: under the environment of 22+2°C and humidity of 30-70%, the polishing solution (pH=5) prepared with WO0.8 cerium oxide micropowder and polyurethane polishing pad are used to roughly polish the polished sample, and the thickness of each surface removed is about 10 u m, and the sand holes and deep scratches on the working surface were basically removed, and the parallelism between the upper and lower surfaces was 20 " (for (110) plane, there is no such index, only the thickness uniformity of sample block is used for monitoring). Then, using the suspension mixture of W0.8 cerium oxide polishing solution and colloidal silica as polishing solution, asphalt as polishing disk material, the square block was finely polished. The thickness of each surface removed was less than 10 um, and the surface shape was M8 after finely polishing. The root mean square roughness RMS was 0.89 nm, and the parallelism between upper and lower surfaces was less than 5 ".

(6) unloading plate and processing of other four surfaces: cleaning the processed surface after the fine polishing in the step (5) with acetone and alcohol in sequence in an ultra-clean workbench, uniformly spin-coating a layer of shellac chips as protective paint, standing for 30min, drying in the air, and heating by using a baking lamp to 507074 remove fixture. Then two rounds of steps (3)-(6) were performed on the remaining three unpolished surfaces to obtain five-sided polished KTN crystals with crystal orientations of (100), (010), (001) and (110) on each surface, with crystal orientation error less than 5, no damage to the surface, root mean square roughness RMS <1 nm and parallelism of the upper and lower surfaces <5”. The schematic diagram of the shape and crystal orientation of the processed KTN sample block is shown in Fig. 3.

The grinding process of step (4) and the polishing process of step (5) in example 3 adopt UNIPOL-802 double-station automatic grinding and polishing machine (Kejing Auto-Instrument Co., LTD) to carry out machine grinding and polishing, and adopt special mold components to efficiently realize the processing goal.

Example 4 Processing of a high-precision cubic KTN single crystal substrate element, wherein the KTN crystal component is K Tao. sNbo. 503 and the crystal phase is cubic (M3M). (100) crystal plane directional fine polishing was carried out and the target shape is a regular hexagonal columnar sample with a width of Smm x a height of Smm, the processing step is different from the one described in example 1 in that: step (2) firstly, a crystal sample block with a length, width and height of 4.85 mm x

5.5 mm x 5.5 mm is cut out by using an inner circle cutting machine, wherein the (100) directional plane is a 4.85 mm x 5.5 mm surface, and then a regular hexagonal column crystal sample block is cut out perpendicular to the (100) directional plane by using a dicing cutting machine, the hexagonal surface of which is (100) directional plane. The processing operation is carried out by using a square fixture with the same material and size as that of example 1, and finally a hexagonal columnar Cu: KTaosNbosO3 crystal substrate element as shown in Fig. 4 was obtained. Its hexagonal crystal plane is (100) finely polished, with no damage, crystal orientation error less than 5 ', root mean square roughness RMS < Inm, and parallelism between upper and lower surfaces < 5 ".

Claims (5)

CLAIMS LU501074

1. A method for processing a single crystal substrate element of potassium tantalum-niobate, the potassium tantalum-niobate single crystal is referred to as KTN crystal, which is KTa;.xNbxO3; or M:K Ta:-«NbxO3 crystal, wherein O<x<1, the crystal phase is cubic, tetragonal or orthogonal, and the doping ion M is selected from one or more of Cu, Fe, Sn, Ti, Li, Na, Mn , wherein the method comprises: (1) orientation: orienting the KTN crystal comprises orienting the single crystal crystallization planes and the internal growth striation according to the crystallization and growth characteristics of the KTN crystal; (2) cutting: taking the directional plane of the crystal as a reference, using a cutting tool to cut a crystal sheet with a designed crystal direction and size, wherein the cutting size error is less than 10 um and the crystal direction error is less than 0.5°; (3) formula: selecting glass or crystal with hardness and elastic modulus similar to that of the processed KTN crystal as a fixture material, designing the shape and size of the fixture according to the geometric size of the crystal processing surface, and manufacturing the fixture by cutting and shaping; selecting paraffin or 502 adhesive to combine the crystal and the fixture into a processing square block according to the application requirement and the Curie temperature value of the crystal sheet; (4) grinding: under the environment of 20-25 °C and humidity of 30-70%, according to the hardness characteristic of KTN crystal, the square block is shaped by using an abrasive, and rough grinding, fine grinding and further fine grinding are carried out, wherein the roughness RMS of the sample after fine grinding is within 150 um, and the thickness uniformity is less than or equal to 2 um; the abrasive of shaping, coarse grinding or fine grinding is selected from carborundum, boron carbide and aluminum oxide; (5) polishing: under the environment of 22+2 °C and humidity of 30-70%, according to the mechanic-chemical properties of KTN crystal, the crystal after fine grinding is roughly polished and finely polished by using a water-based polishing solution and a polishing pad with the abrasive grain size less than 1 um, the surface after fine polishing can be non-damaged, the surface shape is better than A/8, the root mean square roughness (RMS) is less than 1 nm, and the parallelism of the upper HUS0T074 surface and the lower surface is within 5"; the abrasive of the water-based polishing solution is selected from diamond, cerium oxide and silicon dioxide; the polishing pad is selected from polyurethane polishing pad, non-woven fabric polishing pad, > flannelette polishing pad and asphalt polishing pad, (6) coating protective film and unloading plate: cleaning the processed surface after fine polishing with acetone and alcohol in sequence in an ultra-clean workbench by using dust-free cloth, self-leveling or spin-coating a layer of alcohol solution of shellac chips as protective paint, wherein the concentration of the alcohol solution of shellac chips is Swt %-20wt%, standing for 30 min, drying in the air, heating to 60-70 °C by using a baking lamp to melt paraffin, and unloading.

2. The method according to claim 1, wherein the cutting tool in step (2) is a diamond saw or dicing blade or wire cutting machine, the wire cutting speed is 1000-1500 cm/s and the cutting feed speed is 4-8 mm/min.

3. The method according to Claim 2, wherein the fixture material in step (3) is KTN crystal material; the ratio of the processing area of crystal sheet to the fixture processing area is 1:50-1: 2; in the step (5), polyurethane polishing pad is used for rough polishing and asphalt polishing pad 1s used for fine polishing.

4. The method according to Claim 3, wherein the ratio of the processing area of crystal sheet to the fixture processing area is 1:15-1:5.

5. The method according to claim 4, wherein in the step (5), a self-prepared highly efficient dispersed acidic water-based WO.8 cerium oxide polishing liquid is used for rough polishing, which comprises: 0.5 wt%-5wt% WO0.8 cerium oxide micropowder, 55 wt%-70wt% deionized water, 0.2 wt%-15wt% KMnO4, 3wt%-10wt% ethylene glycol, 0.1 wt%-1wt% potassium nitrate, 0-1wt% nitric acid, 0-1wt% potassium hydroxide and 0.1 wt%-2wt% polyacrylic acid (PAA).