Potassium niobium germanate compounds and potassium niobium germanate nonlinear optical / electro-optical crystals, methods of making and uses thereof

Abstract

The application discloses a potassium niobium germanate compound and a potassium niobium germanate nonlinear optical / electro-optical crystal, and a preparation method and application thereof. The chemical formula of the compound is KNbGeO5, the molecular weight is 284.60, the space group is Pna21, the compound belongs to an orthorhombic system, and the cell parameter Z is 8. The compound is prepared by a solid phase synthesis method, and the crystal is obtained by a high-temperature solution method or a hydrothermal method. The crystal has nonlinear optical effect and electro-optical effect, the frequency doubling effect of the crystal is about 11-12 times of that of KH2PO4 (KDP), the ultraviolet cutoff edge is 270 nm, the infrared cutoff edge is 7.25 microns, the light transmission range is wide, and the physical and chemical properties are stable, so that the crystal has important applications in the fields of nonlinear optics, laser technology and electro-optical modulation.

Description

Technical Field

[0001] This invention belongs to the field of optoelectronic functional materials, and relates to a potassium niobate compound and a potassium niobate nonlinear optical / electro-optic crystal, their preparation methods, and their applications in the fields of nonlinear optics and electro-optics. Background Technology

[0002] Nonlinear optical crystals are a class of novel functional materials widely used in optoelectronic technology, with important applications in laser frequency conversion, electro-optic modulation, optoelectronic communication, optical information processing, integrated circuits, and photorefractive crystal memory and storage. Some nonlinear optical crystals are also excellent electro-optic crystals, most notably KH₂PO₄ (KDP), LiNbO₃ (LN), and KTa. x Nb 1-x Materials such as O3 (KTN), CuCl, KTiOPO4 (KTP), and β-BaB2O4 (BBO) are used. With the development of laser technology, more and higher requirements are being placed on the physical and chemical properties of nonlinear optical materials. In particular, new nonlinear optical crystals are required to possess higher nonlinear effects, wider transmission ranges, and larger band gaps for application in higher-power laser output. As electro-optic crystals, the aforementioned nonlinear optical crystals all face insurmountable problems in practical applications: KDP is prone to deliquescence, making crystal processing difficult and increasing production costs; LN has a low laser damage threshold and a high half-wave voltage; KTN is difficult to grow into high-quality, large-size, optically homogeneous single crystals; CuCl has an unfavorable phase transition point at 407℃, making it difficult to grow into high-quality, large-size, optically homogeneous single crystals; KTP crystals are prone to "gray streaks" during use and exhibit significantly increased absorption of visible light, leading to crystal heating, reduced frequency doubling efficiency, decreased output power, and ultimately crystal breakage, thus severely limiting their application in high-power, high-repetition-rate laser devices; BBO has a high laser damage threshold and is currently the preferred choice for high-power lasers, but it is difficult to grow thick along the c-axis and has a high half-wave voltage. Therefore, exploring novel multifunctional crystals with excellent performance that combine nonlinear optical and electro-optic effects is a significant challenge. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a novel potassium niobate (KNbGeO5) compound and a potassium niobate nonlinear optical / electro-optic crystal, along with their preparation methods and applications. This crystal exhibits strong nonlinear optical effects (its powder frequency doubling effect is 11-12 times that of KH₂PO₄ (KDP),) a wide transmission range (0.27-7.25 μm), and a large band gap (4.59 eV), while also possessing excellent electro-optic properties. Furthermore, the crystal prepared by this invention does not absorb moisture when exposed to air, exhibits good physical properties, and is easy to grow.

[0004] The present invention achieves the aforementioned technical effect through the following technical solution:

[0005] This invention provides a potassium niobate germanate compound with the chemical formula KNbGeO5.

[0006] The present invention also provides a method for preparing the potassium niobate germanate compound, comprising preparing the potassium niobate germanate compound by solid-state sintering a compound containing K, Nb2O5 and GeO2.

[0007] According to an embodiment of the present invention, the molar ratio of the K-containing compound, Nb2O5 and GeO2 can be (1-2):(0.8-2):(0.8-2), with exemplary ratios of 1:0.8:0.8, 1:1:1, 1:0.8:2, 1:1:2, 1:2:0.8, and 2:1:2.

[0008] According to an embodiment of the present invention, the temperature of the solid-state sintering method is 850-950°C, and exemplary values ​​are 850°C, 870°C, 880°C, 900°C, 910°C, 920°C, and 950°C; the isothermal time of the solid-state sintering method is 24-240 hours, and exemplary values ​​are 24 hours, 48 ​​hours, 72 hours, 96 hours, 120 hours, 140 hours, and 240 hours.

[0009] According to an embodiment of the present invention, the compound containing the element K is K2CO3, KHCO3, K2SO3, KNO3, or KOH.

[0010] According to an embodiment of the present invention, the sintered product can also be removed and ground during the solid-state sintering process. For example, the grinding can be performed once, twice, or more.

[0011] According to an embodiment of the present invention, the preparation method of the potassium niobate germanate compound comprises the following steps:

[0012] A compound containing potassium (K), Nb₂O₅, and GeO₂ were mixed and sintered at 850–950 °C for 24–240 hours to obtain potassium niobate germanate.

[0013] The present invention also provides a potassium niobium germanate KNbGeO5 crystal.

[0014] According to an embodiment of the present invention, the potassium niobate germanate (KNbGeO5) crystal has a non-centrosymmetric structure, belongs to the orthorhombic crystal system, has a space group of Pna21, and has a unit cell parameter of...

[0015] According to an embodiment of the present invention, the unit cell volume of the potassium niobate KNbGeO5 crystal is...

[0016] According to an embodiment of the present invention, the number of molecules in the unit cell of the potassium niobate KNbGeO5 crystal is Z = 8.

[0017] According to an embodiment of the present invention, the molecular weight of the potassium niobate KNbGeO5 crystal is 284.60.

[0018] According to an embodiment of the present invention, the powder frequency doubling effect of the potassium niobate KNbGeO5 crystal is 11 to 12 times that of KH2PO4 (KDP).

[0019] According to an embodiment of the present invention, the infrared cutoff edge of the potassium niobate KNbGeO5 crystal is 7.25 μm, which can be applied to the 3-5 μm wavelength band.

[0020] According to an embodiment of the present invention, the ultraviolet absorption edge of the potassium niobate KNbGeO5 crystal reaches 0.27 μm, making it applicable to the ultraviolet band.

[0021] According to an embodiment of the present invention, the potassium niobate KNbGeO5 crystal has the following properties: Figure 1 The crystal structure shown.

[0022] According to an embodiment of the present invention, the potassium niobate KNbGeO5 crystal has essentially the following properties: Figure 2 The X-ray diffraction pattern shown.

[0023] The present invention also provides a method for preparing the potassium niobate KNbGeO5 crystal, including the method for preparing the potassium niobate compound described above.

[0024] According to an embodiment of the present invention, the preparation method further includes obtaining potassium niobate KNbGeO5 crystals from the potassium niobate compound obtained after the reaction is completed by a high-temperature solution method or a hydrothermal method.

[0025] Preferably, the method for obtaining potassium niobate KNbGeO5 crystals by the high-temperature solution method includes melting potassium niobate compound and flux at high temperature to obtain a mixed solution, then obtaining KNbGeO5 seed crystals by spontaneous crystallization through cooling, and then obtaining potassium niobate KNbGeO5 crystals through crystal growth.

[0026] Preferably, the molar ratio of the potassium germanate compound to the flux is 1:0.1 to 5, with examples being 1:0.1, 1:0.5, 1:1, 1:2, 1:4, 1:4.5, and 1:5.

[0027] Preferably, the flux is at least one selected from KF-B2O3, KF-MoO3, K2CO3-B2O3, K2CO3-MoO3, K2CO3-WO3, K2CO3-KH2PO4, K2CO3-MoO3-B2O3, K2CO3-MoO3-KH2PO4, K2CO3-MoO3-K2SO4, and K2CO3-MoO3-KF.

[0028] Preferably, the high-temperature melting temperature is 850–1000°C, with examples being 850°C, 870°C, 880°C, 890°C, 900°C, 910°C, 920°C, 930°C, 950°C, 960°C, and 1000°C; the constant temperature melting time is 10–240 hours, with examples being 10 hours, 24 hours, 36 hours, 48 ​​hours, 60 hours, 72 hours, 96 hours, 120 hours, 140 hours, 144 hours, 168 hours, and 240 hours.

[0029] Preferably, the method for obtaining KNbGeO5 seed crystals by spontaneous crystallization by cooling includes slowly cooling the obtained mixed solution to 750-800°C (e.g., 780°C) at a rate of 0.1-3°C / h, and then cooling it to room temperature at a rate of 5-15°C / h to obtain KNbGeO5 seed crystals by spontaneous crystallization.

[0030] Preferably, the method for growing potassium niobium germanate (KNbGeO5) crystals includes: slowly lowering a seed crystal rod (with a seed crystal attached) to the surface of a mixed solution obtained by high-temperature melting; turning on the crystal rotation (e.g., rotation speed 3-35 rpm); slowly cooling to 750-800°C (e.g., 780°C) at a rate of 0.1-3°C / h; lifting the crystal off the liquid surface; and cooling to room temperature from 750-800°C (e.g., 780°C) at a rate of 5-15°C / h to obtain potassium niobium germanate (KNbGeO5) crystals.

[0031] According to an embodiment of the present invention, the preparation method of the potassium niobium germanate KNbGeO5 crystal includes the following steps:

[0032] (a) A compound containing K, Nb2O5 and GeO2 are mixed and sintered at 850-950°C for 24-240 hours. The mixture is taken out and ground several times during the process to obtain compound KNbGeO5.

[0033] (b) Grind the compound KNbGeO5 obtained in step (a) with a flux at a molar ratio of 1:0.1 to 5, and then melt it at a constant temperature of 850 to 1000 °C for 10 to 240 hours to obtain a mixed solution;

[0034] (c) Preparation of seed crystals: The mixed solution obtained in step (b) is slowly cooled to 750-800°C (e.g., 780°C) at a rate of 0.1-3°C / h, and then cooled to room temperature at a rate of 5-15°C / h to spontaneously crystallize and obtain KNbGeO5 seed crystals.

[0035] (d) Crystal growth: The seed crystal rod with the seed crystal attached is slowly lowered to contact the surface of the mixed solution obtained in step (b), the crystal rotation is turned on (rotation speed 3-35 rpm), and the temperature is slowly reduced to 750-800℃ (e.g. 780℃) at a rate of 0.1-3℃ / h. The crystal is lifted off the liquid surface and cooled from 750-800℃ (e.g. 780℃) to room temperature at a rate of 5-15℃ / h to obtain potassium niobium germanate KNbGeO5 crystals.

[0036] Preferably, the method for growing potassium niobate germanate crystals by hydrothermal method includes the following steps:

[0037] (a) A compound containing K, Nb2O5 and GeO2 were mixed and sintered at 850-950°C for 24-240 hours (with several grindings during the process) to obtain compound KNbGeO5;

[0038] (b) Dissolve the compound KNbGeO5 obtained in step (a) in water (preferably, the mass ratio of KNbGeO5 to water is 1:(15-25)), and treat it with ultrasound at 45-75°C to mix it, and then (preferably, use LiOH·H2O, NaOH or KOH) adjust the pH value to 8-11;

[0039] (c) The mixed solution obtained in step (b) is heated to 350-500°C and kept at that temperature for 20-40 days; then cooled to room temperature at a rate of 5-15°C / h (preferably, the sample is washed with water and ethanol after cooling) to obtain potassium niobium germanate KNbGeO5 crystals.

[0040] The present invention also provides a nonlinear optical crystal and / or electro-optic crystal material, which is the potassium niobate KNbGeO5 crystal.

[0041] The present invention also provides the use of the potassium niobate germanate compound and / or the potassium niobate Germanate KNbGeO5 crystal in the fields of nonlinear optics, laser technology, optical parametric amplification or oscillation, electro-optic modulation, and photorefractive information processing;

[0042] Preferably, the potassium niobate compound and / or the potassium niobate KNbGeO5 crystal are used in frequency doubling generators and / or electro-optic crystal devices.

[0043] The present invention also provides an optical device comprising the above-mentioned potassium niobate germanate compound and / or the potassium niobate germanate KNbGeO5 crystal.

[0044] According to an embodiment of the present invention, the optical device may be a frequency doubling generator or an electro-optic crystal device.

[0045] The beneficial effects of this invention:

[0046] (1) The potassium niobate KNbGeO5 crystal of the present invention outputs strong 532nm light (i.e., second harmonic generation) under 1064nm laser irradiation. Its powder frequency doubling effect is 11-12 times that of KH2PO4 (KDP), and it can achieve phase matching. Simultaneously, the crystal of the present invention exhibits electro-optic effects. Therefore, the crystal of the present invention has promising applications in nonlinear optics, laser technology, optical parametric amplification or oscillation, electro-optic modulation, and photorefractive information processing.

[0047] (2) The potassium niobate KNbGeO5 crystal of the present invention has a wide light transmission range (0.27-7.25μm) and can be applied to the ultraviolet and mid-infrared bands.

[0048] (3) The potassium niobate KNbGeO5 crystal of the present invention has stable physicochemical properties, does not deliquesce, and is easy to process and store.

[0049] (4) The method for preparing potassium niobate KNbGeO5 crystals of the present invention is simple, has a fast growth rate, is easy to obtain large-size crystals, and has low cost. Attached Figure Description

[0050] Figure 1 This is a structural diagram of the KNbGeO5 crystal obtained in Example 6 of the present invention;

[0051] Figure 2 The powder X-ray spectrum of the KNbGeO5 crystal prepared in Example 6 of this invention;

[0052] Figure 3 The diagram shows the working principle of a typical nonlinear optical device made from KNbGeO5 crystal according to the present invention, wherein: 1 is a laser, 2 is a lens, 3 is a KNbGeO5 crystal, 4 is a prism, and 5 is a filter.

[0053] Figure 4 This is a schematic diagram illustrating the working principle of a typical electro-optic device made from KNbGeO5 crystal according to the present invention. In the diagram: 6 is a laser, 7 is a polarizer, 8 is a KNbGeO5 crystal, 9 is an analyzer, the electric field direction is the X direction, and the light transmission direction is the Z direction. Detailed Implementation

[0054] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0055] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0056] Example 1

[0057] Preparation of compound KNbGeO5:

[0058] According to the reaction formula: K₂CO₃ + Nb₂O₅ + 2GeO₂ → 2KNbGeO₅ + CO₂↑, compound KNbGeO₅ was synthesized by solid-state synthesis.

[0059] K2CO3, Nb2O5 and GeO2 were mixed evenly in a molar ratio of 1:1:2, placed in a platinum crucible, heated to 900℃ in a muffle furnace, and kept at that temperature for 72 hours. The mixture was then removed and ground several times during the process to obtain the compound KNbGeO5.

[0060] Example 2

[0061] Preparation of compound KNbGeO5:

[0062] According to the reaction formula: 2KHCO3+Nb2O5+2GeO2→2KNbGeO5+H2O+2CO2↑, compound KNbGeO5 was synthesized by solid-state synthesis.

[0063] KHCO3, Nb2O5 and GeO2 were mixed evenly in a molar ratio of 2:1:2 and placed in a platinum crucible. The mixture was heated to 880°C in a muffle furnace and kept at that temperature for 140 hours. The mixture was removed and ground several times during the process to obtain the compound KNbGeO5.

[0064] Example 3

[0065] Preparation of compound KNbGeO5:

[0066] According to the reaction formula: K₂SO₃ + Nb₂O₅ + 2GeO₂ → 2KNbGeO₅ + SO₂↑, compound KNbGeO₅ is synthesized by solid-state reaction method.

[0067] K2SO3, Nb2O5 and GeO2 were mixed homogeneously in a molar ratio of 1:1:2, placed in a platinum crucible, and heated to 920°C in a muffle furnace. The mixture was kept at this temperature for 96 hours, and then ground several times during the process to obtain the compound KNbGeO5.

[0068] Example 4

[0069] Preparation of compound KNbGeO5:

[0070] According to the reaction formula: 4KNO3 + 2Nb2O5 + 4GeO2 → 4KNbGeO5 + 4NO2↑ + O2↑, compound KNbGeO5 was synthesized by solid-state synthesis.

[0071] KNO3, Nb2O5 and GeO2 were mixed homogenously in a molar ratio of 2:1:2, placed in a platinum crucible, and heated to 910°C in a muffle furnace. The mixture was kept at this temperature for 120 hours, and then ground several times during the process to obtain the compound KNbGeO5.

[0072] Example 5

[0073] Preparation of compound KNbGeO5:

[0074] According to the reaction formula: 2KOH + Nb₂O₅ + 2GeO₂ → 2KNbGeO₅ + H₂O, compound KNbGeO₅ was synthesized by solid-state synthesis.

[0075] KOH, Nb2O5 and GeO2 were mixed homogeneously in a molar ratio of 2:1:2, placed in a platinum crucible, and heated to 870°C in a muffle furnace. The mixture was kept at this temperature for 48 hours, and then ground several times during the process to obtain the compound KNbGeO5.

[0076] Example 6

[0077] High-temperature solution growth of KNbGeO5 crystals:

[0078] The compound KNbGeO5 prepared according to Example 1 was mixed with flux KF-B2O3 in a molar ratio of 1:1:2 and placed in a platinum crucible. The mixture was heated to 900°C and kept at that temperature for 48 hours to allow the solution to be homogenized and thoroughly dissolved.

[0079] Preparation of seed crystals: The obtained mixed solution was placed in a single crystal furnace and slowly cooled to 780°C at a rate of 0.1°C / h, and then cooled to room temperature at a rate of 10°C / h to obtain KNbGeO5 seed crystals;

[0080] Crystal growth: The seed crystal rod with the seed crystal attached is slowly lowered to contact the surface of the mixed solution. The crystal rotation is turned on and the rotation speed is adjusted to 8 rpm. The temperature is reduced to 780℃ at a rate of 0.1℃ / h. The crystal is lifted off the liquid surface and cooled from 780℃ to room temperature at a rate of 10℃ / h. Then the crystal is taken out of the single crystal furnace to obtain a KNbGeO5 crystal with a size of 13mm×10mm×11mm.

[0081] The schematic diagram of the single-cell structure of the KNbGeO5 crystal prepared in this embodiment is shown below. Figure 1As shown. The obtained KNbGeO5 crystal has a non-centrosymmetric structure, belongs to the orthorhombic crystal system, has a space group of Pna21, and a unit cell parameter of... Z = 8, unit cell volume is

[0082] The X-ray powder diffraction pattern of the KNbGeO5 crystal prepared in this embodiment is as follows: Figure 2 As shown in the figure, the results indicate that the KNbGeO5 crystal obtained in this embodiment is a single pure phase with high purity.

[0083] Example 7

[0084] High-temperature solution growth of KNbGeO5 crystals:

[0085] The compound KNbGeO5 prepared according to Example 2 was mixed with the flux at a molar ratio of KF-MoO3 of 1:1:3, and then placed in a platinum crucible. The mixture was heated to 920°C and kept at that temperature for 36 hours to allow the solution to be homogenized and thoroughly dissolved.

[0086] Preparation of seed crystals: The obtained mixed solution was placed in a single crystal furnace and slowly cooled to 780℃ at a rate of 0.2℃ / h, and then cooled to room temperature at a rate of 10℃ / h to obtain KNbGeO5 seed crystals;

[0087] Crystal growth:

[0088] The seed crystal rod with the seed crystal attached is slowly lowered to contact the surface of the mixed solution. The crystal rotation is turned on and the rotation speed is adjusted to 6 rpm. The temperature is reduced to 780℃ at a rate of 0.2℃ / h. The crystal is lifted off the liquid surface and cooled from 780℃ to room temperature at a rate of 10℃ / h. Then the crystal is taken out of the single crystal furnace to obtain a KNbGeO5 crystal with a size of 11mm×13mm×11mm.

[0089] Example 8

[0090] High-temperature solution growth of KNbGeO5 crystals:

[0091] The compound KNbGeO5 prepared according to Example 2 was mixed with the flux K2CO3-B2O3 in a molar ratio of 1:1.5:1 and placed in a platinum crucible. The mixture was heated to 930°C and kept at that temperature for 60 hours to allow the solution to dissolve completely.

[0092] Preparation of seed crystals: The obtained mixed solution was placed in a single crystal furnace and slowly cooled to 780°C at a rate of 0.3°C / h, and then cooled to room temperature at a rate of 10°C / h to obtain KNbGeO5 seed crystals;

[0093] Crystal growth:

[0094] The seed crystal rod with the seed crystal attached is slowly lowered to contact the surface of the mixed solution. The crystal rotation is turned on and the rotation speed is adjusted to 10 rpm. The temperature is reduced to 780℃ at a rate of 0.3℃ / h. The crystal is lifted off the liquid surface and cooled from 780℃ to room temperature at a rate of 10℃ / h. Then the crystal is taken out of the single crystal furnace to obtain a KNbGeO5 crystal with a size of 7mm×8mm×5mm.

[0095] Example 9

[0096] High-temperature solution growth of KNbGeO5 crystals:

[0097] The compound KNbGeO5 prepared according to Example 4 was mixed with flux K2CO3-MoO3 in a molar ratio of 1:2:2 and placed in a platinum crucible. The mixture was heated to 950°C and kept at that temperature for 120 hours to allow the solution to be homogenized and thoroughly dissolved.

[0098] Preparation of seed crystals: The obtained mixed solution was placed in a single crystal furnace and slowly cooled to 780°C at a rate of 0.5°C / h, and then cooled to room temperature at a rate of 10°C / h to obtain KNbGeO5 seed crystals;

[0099] Crystal growth:

[0100] The seed crystal rod with the seed crystal attached is slowly lowered to contact the surface of the mixed solution. The crystal rotation is turned on and the rotation speed is adjusted to 9 rpm. The temperature is reduced to 780℃ at a rate of 0.5℃ / h. The crystal is lifted off the liquid surface and cooled from 780℃ to room temperature at a rate of 10℃ / h. Then the crystal is taken out of the single crystal furnace to obtain a KNbGeO5 crystal with a size of 6mm×3mm×8mm.

[0101] Example 10

[0102] High-temperature solution growth of KNbGeO5 crystals:

[0103] The compound KNbGeO5 prepared according to Example 5 was mixed with flux K2CO3-WO3 in a molar ratio of 1:1.5:3 and placed in a platinum crucible. The mixture was heated to 960°C and kept at that temperature for 72 hours to allow the solution to dissolve completely.

[0104] Preparation of seed crystals: The obtained mixed solution was placed in a single crystal furnace and slowly cooled to 780°C at a rate of 0.7°C / h, and then cooled to room temperature at a rate of 10°C / h to obtain KNbGeO5 seed crystals;

[0105] Crystal growth: The seed crystal rod with the seed crystal attached is slowly lowered to contact the surface of the mixed solution. The crystal rotation is turned on and the rotation speed is adjusted to 7 rpm. The temperature is reduced to 780℃ at a rate of 0.7℃ / h. The crystal is lifted off the liquid surface and cooled from 780℃ to room temperature at a rate of 10℃ / h. Then the crystal is taken out of the single crystal furnace to obtain a KNbGeO5 crystal with a size of 8mm×10mm×7mm.

[0106] Example 11

[0107] High-temperature solution growth of KNbGeO5 crystals:

[0108] The compound KNbGeO5 prepared according to Example 2 was mixed with the flux K2CO3-KH2PO4 in a molar ratio of 1:0.5:0.5 and placed in a platinum crucible. The mixture was heated to 880°C and kept at that temperature for 140 hours to allow the solution to dissolve completely.

[0109] Preparation of seed crystals: The obtained mixed solution was placed in a single crystal furnace and slowly cooled to 780°C at a rate of 1.3°C / h, and then cooled to room temperature at a rate of 10°C / h to obtain KNbGeO5 seed crystals;

[0110] Crystal growth: The seed crystal rod with the seed crystal attached is slowly lowered to contact the surface of the mixed solution. The crystal rotation is turned on and the rotation speed is adjusted to 10 rpm. The temperature is reduced to 780℃ at a rate of 1.3℃ / h. The crystal is lifted off the liquid surface and cooled from 780℃ to room temperature at a rate of 10℃ / h. Then the crystal is taken out of the single crystal furnace to obtain a KNbGeO5 crystal with a size of 11mm×10mm×15mm.

[0111] Example 12

[0112] High-temperature solution growth of KNbGeO5 crystals:

[0113] The compound KNbGeO5 prepared according to Example 2 was mixed with the flux K2CO3-MoO3-B2O3 in a molar ratio of 1:1:1:0.5 and placed in a platinum crucible. The mixture was heated to 890°C and kept at that temperature for 96 hours to allow the solution to be homogenized and thoroughly dissolved.

[0114] Preparation of seed crystals: The obtained mixed solution was placed in a single crystal furnace and slowly cooled to 780℃ at a rate of 0.4℃ / h, and then cooled to room temperature at a rate of 10℃ / h to obtain KNbGeO5 seed crystals;

[0115] Crystal growth: The seed crystal rod with the seed crystal attached is slowly lowered to contact the surface of the mixed solution. The crystal rotation is turned on and the rotation speed is adjusted to 10 rpm. The temperature is reduced to 780℃ at a rate of 0.4℃ / h. The crystal is lifted off the liquid surface and cooled from 780℃ to room temperature at a rate of 10℃ / h. Then the crystal is taken out of the single crystal furnace to obtain a KNbGeO5 crystal with a size of 11mm×10mm×15mm.

[0116] Example 13

[0117] High-temperature solution growth of KNbGeO5 crystals:

[0118] The compound KNbGeO5 prepared according to Example 1 was mixed with the flux K2CO3-MoO3-KH2PO4 in a molar ratio of 1:2:0.5:0.5 and placed in a platinum crucible. The mixture was heated to 910°C and kept at that temperature for 144 hours to allow the solution to dissolve completely.

[0119] Preparation of seed crystals: The obtained mixed solution was placed in a single crystal furnace and slowly cooled to 780℃ at a rate of 0.6℃ / h, and then cooled to room temperature at a rate of 10℃ / h to obtain KNbGeO5 seed crystals;

[0120] Crystal growth: The seed crystal rod with the seed crystal attached is slowly lowered to contact the surface of the mixed solution. The crystal rotation is turned on and the rotation speed is adjusted to 10 rpm. The temperature is reduced to 780℃ at a rate of 0.6℃ / h. The crystal is lifted off the liquid surface and cooled from 780℃ to room temperature at a rate of 10℃ / h. Then the crystal is taken out of the single crystal furnace to obtain a KNbGeO5 crystal with a size of 12mm×13mm×8mm.

[0121] Example 14

[0122] High-temperature solution growth of KNbGeO5 crystals:

[0123] The compound KNbGeO5 prepared according to Example 5 was mixed with the flux K2CO3-MoO3-K2SO4 in a molar ratio of 1:1.5:1:0.5 and placed in a platinum crucible. The mixture was heated to 870°C and kept at that temperature for 168 hours to allow the solution to dissolve completely.

[0124] Preparation of seed crystals: The obtained mixed solution was placed in a single crystal furnace and slowly cooled to 780°C at a rate of 0.3°C / h, and then cooled to room temperature at a rate of 10°C / h to obtain KNbGeO5 seed crystals;

[0125] Crystal growth: The seed crystal rod with the seed crystal attached is slowly lowered to contact the surface of the mixed solution. The crystal rotation is turned on and the rotation speed is adjusted to 12 rpm. The temperature is reduced to 780℃ at a rate of 0.3℃ / h. The crystal is lifted off the liquid surface and cooled from 780℃ to room temperature at a rate of 10℃ / h. Then the crystal is taken out of the single crystal furnace to obtain a KNbGeO5 crystal with a size of 8mm×11mm×9mm.

[0126] Example 15

[0127] High-temperature solution growth of KNbGeO5 crystals:

[0128] The compound KNbGeO5 prepared according to Example 2 was mixed with flux K2CO3-MoO3-KF in a molar ratio of 1:0.5:1:1.5 and placed in a platinum crucible. The mixture was heated to 890°C and kept at that temperature for 72 hours to allow the solution to dissolve completely.

[0129] Preparation of seed crystals: The obtained mixed solution was placed in a single crystal furnace and slowly cooled to 780℃ at a rate of 0.6℃ / h, and then cooled to room temperature at a rate of 10℃ / h to obtain KNbGeO5 seed crystals;

[0130] Crystal growth: The seed crystal rod with the seed crystal attached is slowly lowered to contact the surface of the mixed solution. The crystal rotation is turned on and the rotation speed is adjusted to 8 rpm. The temperature is reduced to 780℃ at a rate of 0.6℃ / h. The crystal is lifted off the liquid surface and cooled from 780℃ to room temperature at a rate of 10℃ / h. Then the crystal is taken out of the single crystal furnace to obtain a KNbGeO5 crystal with a size of 4mm×6mm×7mm.

[0131] Example 16

[0132] Hydrothermal growth of KNbGeO5 crystals:

[0133] 5g of compound KNbGeO5 prepared in Example 1 was dissolved in 100g of deionized water. The incompletely dissolved mixture was ultrasonically treated at 50°C to ensure thorough mixing. The pH was then adjusted to 9 using LiOH·H2O.

[0134] The resulting mixed solution was transferred into a clean, uncontaminated lining of a hydrothermal reactor, and the reactor was then tightly sealed.

[0135] The hydrothermal reactor was placed in a resistance wire heating furnace and heated to 450℃, then held at that temperature for 25 days. The temperature was then lowered to room temperature at a rate of 8℃ / h, the furnace was turned off, and the sample was allowed to cool before washing with water and ethanol to obtain KNbGeO5 crystals with dimensions of 4mm × 3mm × 5mm.

[0136] Example 17

[0137] Hydrothermal growth of KNbGeO5 crystals:

[0138] 4g of compound KNbGeO5 prepared in Example 3 was dissolved in 100g of deionized water. The incompletely dissolved mixture was ultrasonically treated at 65°C to ensure thorough mixing, and then the pH was adjusted to 10 with NaOH.

[0139] The resulting mixed solution was transferred into a clean, uncontaminated lining of a hydrothermal reactor, and the reactor was then tightly sealed.

[0140] The hydrothermal reactor was placed in a resistance wire heating furnace and heated to 400℃, then held at that temperature for 30 days. The temperature was then lowered to room temperature at a rate of 10℃ / h, the furnace was turned off, and the sample was allowed to cool before washing with water and ethanol to obtain KNbGeO5 crystals with dimensions of 6mm × 2mm × 5mm.

[0141] Example 18

[0142] Hydrothermal growth of KNbGeO5 crystals:

[0143] 6g of compound KNbGeO5 prepared in Example 5 was dissolved in 100g of deionized water. The incompletely dissolved mixture was ultrasonically treated at 55°C to ensure thorough mixing. The pH was then adjusted to 10.5 with KOH.

[0144] The resulting mixed solution was transferred into a clean, uncontaminated lining of a hydrothermal reactor, and the reactor was then tightly sealed.

[0145] The hydrothermal reactor was placed in a resistance wire heating furnace and heated to 380℃, then held at that temperature for 18 days. The temperature was then lowered to room temperature at a rate of 15℃ / h, the furnace was turned off, and the sample was allowed to cool before washing with water and ethanol to obtain KNbGeO5 crystals with dimensions of 4mm × 6mm × 7mm.

[0146] Example 19

[0147] The arbitrary crystals obtained in Examples 6-18 are processed along the phase-matching direction, and then... Figure 3 The device, positioned at position 3, uses an Nd:YAG laser as its light source (laser 1). The infrared beam output from laser 1, with a wavelength of 1064 nm, passes through prism 2 and is incident on the KNbGeO5 single crystal 3. The output beam, consisting of 1064 nm infrared light and 532 nm green light, is split by prism 4 and finally filtered by filter 5 to obtain a green laser with a wavelength of 532 nm. The output intensity (powder frequency doubling effect) of the KNbGeO5 crystal prepared in Example 6 is approximately 11-12 times that of KDP under the same conditions.

[0148] Example 20

[0149] The arbitrary crystals obtained in Examples 6-18 are processed in a certain direction, and then... Figure 4 The device is positioned at position 8 in the apparatus. The light-transmitting surfaces at both ends of the processed device are precision polished and silver-plated electrodes. The light output from the laser 6 passes through the polarizer 7. An external electric field is applied along the X direction, which generates an electro-optic effect in the KNbGeO5 single crystal 8 (the output intensity (powder frequency doubling effect) of the KNbGeO5 crystal prepared in Example 6 is about 4 times that of KDP under the same conditions). The bipolarized light output from the crystal passes through the analyzer 9 to generate modulated light.

[0150] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A potassium niobate potassium KNbGeO5 crystal, characterized in that, The potassium niobate germanate KNbGeO5 crystal has a non-centrosymmetric structure, belongs to the orthorhombic crystal system, has a space group of Pna21, and has cell parameters of a=13.426(7) Å, b=6.660(3) Å, c=11.069(5) Å, and Z=8.

2. The method for preparing potassium niobium germanate (KNbGeO5) crystals according to claim 1, characterized in that, The preparation method includes preparing potassium niobate germanate compound by solid-state sintering a compound containing K, Nb2O5, and GeO2.

3. The preparation method according to claim 2, characterized in that, The molar ratio of the K-containing compound, Nb2O5, and GeO2 is (1-2):(0.8-2):(0.8-2). And / or, the K-containing compound is K2CO3, KHCO3, K2SO3, KNO3, or KOH.

4. The preparation method according to claim 2, characterized in that, The solid-state sintering temperature is 850~950℃; the isothermal time of the solid-state sintering is 24~240 hours.

5. The preparation method according to any one of claims 2-4, characterized in that, The preparation method further includes obtaining potassium niobate KNbGeO5 crystals from the potassium niobate compound obtained after the reaction is completed using a high-temperature solution method or a hydrothermal method.

6. The preparation method according to claim 5, characterized in that, The method for obtaining potassium niobate KNbGeO5 crystals by high-temperature solution method includes melting potassium niobate compound and flux at high temperature to obtain a mixed solution, then obtaining KNbGeO5 seed crystals by spontaneous crystallization through cooling, and then obtaining potassium niobate KNbGeO5 crystals through crystal growth.

7. The preparation method according to claim 6, characterized in that, The molar ratio of the potassium germanate compound to the flux is 1:0.1~5.

8. The preparation method according to claim 6, characterized in that, The flux is at least one of KF-B2O3, KF-MoO3, K2CO3-B2O3, K2CO3-MoO3, K2CO3-WO3, K2CO3-KH2PO4, K2CO3-MoO3-B2O3, K2CO3-MoO3-KH2PO4, K2CO3-MoO3-K2SO4, and K2CO3-MoO3-KF.

9. The preparation method according to claim 6, characterized in that, The high-temperature melting temperature is 850~1000℃; the high-temperature melting isothermal time is 10~240 hours.

10. The preparation method according to claim 6, characterized in that, The method for obtaining KNbGeO5 seed crystals by spontaneous crystallization at cooling includes slowly cooling the obtained mixed solution to 750-800℃ at a rate of 0.1-3℃ / h, and then cooling it to room temperature at a rate of 5-15℃ / h to obtain KNbGeO5 seed crystals by spontaneous crystallization.

11. The preparation method according to claim 6, characterized in that, The method for growing potassium niobium germanate (KNbGeO5) crystals includes contacting a seed crystal rod with a seed crystal attached to the surface of a mixed solution obtained by high-temperature melting, starting crystal rotation, slowly cooling to 750-800°C at a rate of 0.1-3°C / h, lifting the crystal off the liquid surface, and cooling it to room temperature from 750-800°C at a rate of 5-15°C / h to obtain potassium niobium germanate (KNbGeO5) crystals.

12. The preparation method according to claim 5, characterized in that, The method for growing potassium niobate germanate crystals by hydrothermal method includes the following steps: (a) A compound containing K, Nb2O5 and GeO2 are mixed and sintered at 850~950℃ for 24~240 hours to obtain compound KNbGeO5; (b) Dissolve the compound KNbGeO5 obtained in step (a) in deionized water and mix it by ultrasonic treatment at 45~75℃, and then adjust the pH value to 8~11. (c) The mixed solution obtained in step (b) is heated to 350~500℃ and kept at that temperature for 20~40 days; then cooled to room temperature at a rate of 5~15℃ / h to obtain potassium niobium germanate KNbGeO5 crystals.

13. The preparation method according to claim 12, characterized in that, The mass ratio of KNbGeO5 to water is 1:(15~25).

14. A nonlinear optical crystal and / or electro-optic crystal material, characterized in that, It is the potassium niobate KNbGeO5 crystal as described in claim 1.

15. The use of the potassium niobate KNbGeO5 crystal according to claim 1 in the fields of nonlinear optics, laser technology, optical parametric amplification or oscillation, electro-optic modulation, and photorefractive information processing.

16. An optical device comprising the potassium niobate KNbGeO5 crystal of claim 1.

17. The optical device as claimed in claim 16, characterized in that, The optical device is a frequency multiplier or an electro-optic crystal device.

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