KR101800132B1 - Polar noncentrosymmetric borate-based crystal - Google Patents

Abstract

A polar non-centrosymmetric borate-based crystal of the present invention is represented by structural formula Pb_2BO_3Cl, comprises [Pb_2BO_3]^+ layers containing atom group cations represented by [Pb_2BO_3]^+, and has a structure in which chlorine ions (Cl^-) are disposed between [Pb_2BO_3]^+ layers facing each other.

Description

POLAR NONCENTROSYMMETRIC BORATE-BASED CRYSTAL [0002]

The present invention relates to polar non-center-symmetrical borate-based crystals, and more particularly to polar non-center-symmetric borate-based crystals having high second harmonic generation characteristics.

Nonlinear optical (NLO) materials, a key component for solid-state lasers that generate coherent light through cascaded frequency changes, are widely used in a wide range of scientific and technical applications Attracting attention. There have been many efforts to explain the relationship of structure, composition and NLO properties of crystalline compounds decades ago, but there has been a great deal of effort in describing the appropriate second birefringence for high second harmonic generation (SHG) coefficients, phase- The ability to efficiently design new structured NLO materials with excellent composite properties, including high transparency properties, high transparency windows for high damage thresholds, good chemical stability, and easy crystal growth. Research continues.

Techniques known for developing new NLO materials include anion, second-order Jahn-Teller (SOJT) modified cations in a π-delocalized system (d ⁰ of a twisted octahedral structure Utilizing a non-centrosymmetric chromophore, such as a cation with stereochemically active, non-covalent electron pairs, and a d ¹⁰ metal cation that exhibits polar displacement as a building unit during the synthesis process .

Among them, metal borates are being intensively studied as ultraviolet or far ultraviolet NLO materials. In particular, the development of NLO crystals in borate systems has been successfully performed based on anionic group theory. The nonlinearity of the overall crystal is then obtained by the geometric superposition of the second-order susceptibility of the NLO-active anionic group. A major UV-NLO crystals, known so _{far, β-BaB 2 O 4 (} BBO), LiB 3 O 5 (LBO), CsB 3 O 5 (CBO), CsLiB 6 O 10 (CLBO), YCa 4 O (BO ₃ ) ₃ [YCOB].

The largest breakthrough in the far ultraviolet-NLO crystal was the discovery of KBe ₂ BO ₃ F ₂ (KBBF), the only material capable of generating interference light at wavelengths below 200 nm due to direct SHG response characteristics. The excellent NLO properties of KBBF, with appropriate SHG coefficients, wide transmission window and appropriate birefringence properties, are clearly due to its distinct crystal structure. [Be ₂ BO ₃ F ₂ ] _∞ layers formed of triangular plane units represented by [BO ₂ O ₃ F] and [BO ₃ ] in a chiral structure are arranged in the same plane , Thereby improving the SHG characteristics and birefringence characteristics. The last three oxygen atoms and Be atoms in the BO ₃ group is to prevent the formation of unsaturated bonds (dangling bond) in the BO ₃ groups, as a result, leads to a very short absorption edge in the ultraviolet region (absorption edge). Due to the excellent NLO properties of KBBF due to its structure, many researchers are continuing to develop new NLO crystals with similarly good properties.

Representative compounds of the KBBF family include ABe ₂ B ₃ O _{7 wherein} A is K or Rb, Na ₂ CsBe ₆ B ₅ O ₁₅ , NaSr ₃ Be ₃ B ₃ O ₉ F ₄ , NaCaBe ₂ B ₂ O ₆ F, and Cs ₃ Zn ₆ B ₉ O ₂₁ . Despite these distinguishing characteristics, however, it is very difficult to grow large crystals of the KBBF family by their layered structure.

It is an object of the present invention to provide a polar non-center-symmetric borate-based crystal having a strong second-order harmonic generation efficiency by having a high NLO coefficient and a broad UV transmittance.

Polar non-central symmetry for the work object of the present invention, borate-based crystals are represented by the structural formula Pb ₂ BO ₃ Cl, includes a [Pb ₂ BO _3] ⁺ layer containing an atomic group cation represented by [Pb ₂ BO _3] ^+, And a chlorine ion (Cl < ^- >) is disposed between the [Pb ₂ BO ₃ ] ⁺ layers facing each other.

In one embodiment, the [Pb ₂ BO ₃ ] ⁺ layer is comprised of a BO ₃ triangular unit and the PbO ₃ triangular pyramid, and the ac-plane [Pb ₂ BO ₃ ] ⁺ layer may have a honeycomb structure. At this time, the BO ₃ triangular unit of the [Pb ₂ BO ₃ ] ⁺ layer can share its vertex with the six PbO ₃ triangular pyramids.

In one embodiment, the polar non-center-symmetric borate-based crystals may have a crystal structure of trigonal polar NCS space group, P 321 (No. 150).

In one embodiment, the polar non-center-symmetric borate-based crystals may have an ultraviolet-visible light absorption rate of 80% or greater at a wavelength range of 500 nm to 2500 nm.

In one embodiment, the polar non-center-symmetric borate-based crystals can be applied to any one of a laser device, a nonlinear optical device, a piezoelectric sensor, a wireless communication, a catalyst, a power storage transport device, a computer device or a quantum interference device.

According to the polar non-center-symmetrical borate-based crystals of the present invention, borate-based crystals exhibit a high SHG effect due to the inclusion of lead (Pb) and chlorine (Cl), exhibit a wide distribution of transmittance, have a large nonlinear coefficient, . Accordingly, the polar non-center-symmetric borate-based crystals of the present invention can be usefully used in photonic applications. Using these characteristics, the polar non-center-symmetrical bushel of the present invention can be easily applied to a laser device, a nonlinear optical device, a piezoelectric sensor, a wireless communication device, a catalyst, a power storage transportation device, a computer device or a quantum interference device.

1 is a view for explaining the structure of a polar non-center-symmetrical borate-based crystal according to the present invention.
FIG. 2 is a graph showing the results of thermal analysis, differential scanning calorimetry, and powder XRD analysis of the polar non-center-symmetrical borate-based crystals according to the present invention.
3 is a graph showing the optical characteristics and nonlinear optical property evaluation results of the polar non-center-symmetrical borate-based crystals according to the present invention.
4 is a graph showing the total state density and partial state density (partial DOS, PDOS) of the polar non-center-symmetrical borate-based crystals according to the present invention.
FIG. 5 is a diagram showing a structural analysis result of a polar non-center-symmetrical borate-based crystal according to the present invention. FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention is capable of various modifications and various forms, and specific embodiments are illustrated in the drawings and described in detail in the text. It is to be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but on the contrary, is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Like reference numerals are used for like elements in describing each drawing.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the term "comprises" or "having ", etc. is intended to specify that there is a feature, step, operation, element, part or combination thereof described in the specification, , &Quot; an ", " an ", " an "

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

1 is a view for explaining the structure of a polar non-center-symmetrical borate-based crystal according to the present invention.

1 (a) to 1 (c) show the structure of a compound in a ball-and-stick model in which green balls represent "lead" and orange balls represent "boron (B) (Blue), "blue" means "fluorine (F)", and red means "oxygen (O)", purple means "chlorine (O) ".

1, (a) shows a structure obtained by cutting along the ac-plane of Pb ₂ BO ₃ Cl, (b) shows a structure obtained by cutting along the ac-plane of KBBF (KBe ₂ BO ₃ F ₂ ) (c) shows that the BO ₃ triangular unit on the ab-plane of Pb ₂ BO ₃ Cl shares its vertex with six PbO ₃ triangular pyramids and forms a [Pb ₂ BO ₃ ] ⁺ layer of honeycomb structure.

Referring to (a) of Figure 1, the Pb ₂ BO ₃ Cl is a polar non-central symmetry borate-based crystal according to the invention the space between the [Pb ₂ BO _3] ⁺ layer, and such a [Pb ₂ BO _3] ⁺ layers the chlorine ion in place (Cl ^-) include. The [Pb ₂ BO ₃ ] ⁺ layer is a two-dimensional layered structure composed of a BO ₃ triangular unit and an atomic cations represented by [Pb ₂ BO ₃ ] ⁺ consisting of PbO ₃ triangular pyramids. Pb ₂ BO ₃ Cl is crystallized into triangular polar non-center symmetric space group, P 321 (No. 150).

Referring to (b) of 1 with (a), as a novel compound of KBBF series according to the present invention, Pb ₂ BO ₃ Cl is KBBF of _{^{[K] + [Be 2 BO}} 3 F 2] - in the structural There is a clear difference.

In the present invention, the atomic group cation is a two-dimensional layered structure [Pb ₂ BO _3] ⁺ to form a layer, and [Pb ₂ BO _3] ⁺ chloride ion between the layers (Cl ^-) the charge balance (charge while having an arrangement balance. On the other hand, KBBF is a two-dimensional layered structure _{[Be 2 BO 3 F 2]} - which is formed by the atomic group anion, formed by the atomic group anion represented by _{[Be 2 BO 3 F 2]} - the potassium ion cations between the layers ( K ⁺ ) are arranged in the structure.

That is, [Pb ₂ BO _3] ⁺ lone pair in the layer, the lead ions (Pb ²⁺⁾ is [Be ₂ BO ₃ F _2] of KBBF of the present ^invention as a substitute ^for-fluoride ion from the layer (F) Can be considered.

In the [Pb ₂ BO ₃ ] ⁺ layer of Pb ₂ BO ₃ Cl of the present invention, the unique boron ion (B ³⁺ ) is coordinated to the three oxygen atoms of the BO ₃ plane triangular unit, The BO bond length is 1.370 (17) Å. The lead ion located at the 3 m symmetric site is also bound to three oxygen atoms in the triangular pyramid coordination environment, at which the Pb-O bond length is 2.297 (8) Å.

Referring to FIG. 1 (c), the BO ₃ planar triangular unit forms a [Pb ₂ BO ₃ ] ⁺ layer that shares the corners with six PbO ₃ triangular pyramids and represents a honeycomb structure in the ab-plane .

Specifically, the cooperative interaction of the polarized unpaired electron pairs in the PbO ₃ triangular pyramid and the parallel BO ₃ triangular units oriented in the same direction in the [Pb ₂ BO ₃ ] ⁺ layer are predominantly high macroscopic SHG It can be a major cause of the effect. The _three dangling bonds of the BO ₃ planar triangular unit can be removed by a rigid bond between the three terminal oxygen atoms of the BO ₃ plane triangular unit and the lead atom, which can be useful for broadening transparency.

The bond valence sums for lead and boron ions in Pb ₂ BO ₃ Cl are calculated to be 2.15 and 3.00, respectively.

Compared to the bond length between lead-oxygen and chlorine-oxygen in Pb ₂ BO ₃ Cl, the bond length between beryllium-oxygen in KBBF is 1.636 Å and the bond length between fluorine-oxygen is 2.596 Å, which is relatively short Nevertheless, it can be seen that there is practically no interaction between atoms between beryllium-oxygen and fluorine-oxygen.

The overall network of polar components in the Pb ₂ BO ₃ Cl crystals of the present invention can add synergy to the SHG characteristics and make them very strong. Although the spatial density of [BO ₃ ] ³ group in Pb ₂ BO ₃ Cl is relatively small compared to KBBF, the synergistic effect of the interaction between the unoccupied electron pair of lead ion and chlorine ion, The p-π interaction between lead ions in the [Pb ₂ (BO ₃ )] ⁺ layer and the [BO ₃ ] ³ group can exhibit very high SHG characteristics. Further, the Pb ₂ BO ₃ Cl crystals of the present invention have high birefringence characteristics.

The Pb ₂ BO ₃ Cl crystals having the high SHG effect and the NLO characteristic according to the present invention can be used for various devices such as a laser device, a nonlinear optical device, a piezoelectric sensor, a wireless communication, a catalyst, a power storage transportation device, It can be used in applications.

Hereinafter, the characteristics evaluation and structure confirmation experiment of Pb ₂ BO ₃ Cl crystals according to the present invention and the results thereof will be described in detail with reference to FIG. 2 to FIG. 5.

Production Example 1: Production of a single crystal

A mixture of PbO (Alfa Aesar, 99.5%), PbCl ₂ (Alfa Aesar, 99.9%) and H ₃ BO ₃ (Alfa Aesar, 99%) in a molar ratio of 3: 1: And placed in a sealed fused silica tube.

First, the sealed tube containing the reaction mixture was gradually heated to 720 占 폚 at a heating rate of 50 占 폚 / hour and maintained for 24 hours until it became a clear and clean melt. The melt was then slowly cooled to a final crystallization temperature of 650 占 폚 at a cooling rate of 3 占 폚 / hour. The resultant mixture was cooled to room temperature to obtain a colorless transparent crystal (Pb ₂ BO ₃ Cl).

Production Example 2: Preparation of crystals

A solid state reaction was performed at 600 ° C for 2 days using PbO (Alfa Aesar, 99.5%), PbCl ₂ (Alfa Aesar, 99.9%) and H ₃ BO ₃ (Alfa Aesar, 99% Pb ₂ BO ₃ Cl crystals were prepared. The crystals were submitted to the Noncentrosymmetric Materials Bank (http://ncsmb.knrrc.or.kr).

XRD analysis

The Pb ₂ BO ₃ Cl prepared as described above was analyzed by single crystal X-ray diffraction analysis using a Bruker SMART BREEZE diffractometer equipped with a 1 K CCD area detector using graphite monochromated Mo Kα radiation at room temperature Single crystal XRD) analysis was performed. The structure was solved using the direct method and purified by full matrix matrix least-squares fitting to F ² using SHELX-97. The refined structure was confirmed from the PLATON program using the ADDSYM algorithm and no higher symmetries were found. The results are shown in Table 1 below.

The atomic coordination and equivalent isotropic displacement parameters (U _eq ) for Pb ₂ BO ₃ Cl are also shown in Table 2 below. ^A U _eq in Table 2 defines 1/3 of the trajectory of the orthogonalized U _ij sensor.

In addition, the selected bond length and bonding angle of Pb ₂ BO ₃ Cl are shown in Table 3 below.

^a R ( F ) = Σ || F _o | F _c || / Σ | F _o |

^b R _w ( F _o ² ) = [Σ w ( F _o ² ?? F _c ² ) ² / Σ w ( F _o ² ) ² ] ^1/2

Evaluation of thermal properties

Thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD) were used to evaluate the thermal behavior of Pb ₂ BO ₃ Cl. Analysis was performed. The results are shown in Fig.

PXRD data were collected on a Bruker New D8 Advance diffractometer using Cu Kα radiation at 40 kV and 40 mA at room temperature. Pb ₂ BO ₃ Cl was placed on a sample holder and scanned at a diffraction angle (2 慮) range of 5 to 70 조건 under conditions of a step size of 0.05 와 and a step time of 0.2 seconds.

Pb ₂ BO ₃ Cl was performed using a NETZSCH STA 449C simultaneous analyzer. Pb ₂ BO ₃ Cl was sealed in a separated alumina crucible using Al ₂ O ₃ as a reference material and heated under normal conditions of supplying nitrogen gas at a rate of 10 ° C / minute from room temperature to 750 ° C. Thermogravimetric analysis Residuals were visually identified and heated and analyzed by powder XRD.

FIG. 2 is a graph showing the results of thermal analysis, differential scanning calorimetry, and powder XRD analysis of the polar non-center-symmetrical borate-based crystals according to the present invention.

In FIG. 2, (a) is a graph showing TGA and DSC results, and (b) is a graph showing an experimental PXRD pattern and a calculated PXRD pattern of Pb ₂ BO ₃ Cl.

Referring to FIG. 2 (a), it can be seen that Pb ₂ BO ₃ Cl has no substantial change in weight even though the temperature is increased from 100 ° C. to 640 ° C. through a TGA graph (black graph). That is, it can be seen that Pb ₂ BO ₃ Cl is hardly damaged by heat up to at least 640 ° C. and has excellent heat resistance.

From the DSC graph (blue graph), it can be seen that one endothermic peak appears near 630 ° C due to the melting of Pb ₂ BO ₃ Cl. It can be predicted that the volatility of Pb ₂ BO ₃ Cl at high temperature until melting causes almost negligible weight loss in the TGA graph.

In fact, as shown in FIG.'S 2 (b), through the PXRD pattern of Pb ₂ BO ₃ Cl calculated PXRD pattern (red graph), melted in (black graphs) and melting after (blue graph) of, Pb ₂ BO ₃ Cl can strongly predict the congruently melting property without phase change at all times. Therefore, it can be expected that Pb ₂ BO ₃ Cl single crystal with high quality can be manufactured by various crystal growth methods.

Optical property evaluation

For evaluation of the infrared spectroscopic characteristics, Pb ₂ BO ₃ Cl was introduced into the KBr matrix and an infrared spectrum was obtained using a Thermo Scientific Nicolet 6700FT-IP spectrometer within the range of 400 to 4000 cm ^-1 . In addition, ultraviolet-visible light diffuse reflectance spectral data were obtained using a Varian Cary 500 scan UV-vis-NIR spectrometer at 200 to 250 nm at room temperature. The reflection spectrum was converted into absorbance data using the Kubelka-Munk function expressed by the following equation (1).

[Formula 1]

In the above formula (1), K represents the degree of absorption, R represents the reflectivity, and S represents the degree of scattering. Absorption was obtained by extracting the straight line portion of the upward graph sloping to zero in the K / S and energy (E) plot. The results are shown in Fig.

The powder SHG characteristics were measured using a modified Kurtz and Perry NLO system with 1,064 nm radiation, and as a result, a phase-matching curve of Pb ₂ BO ₃ Cl was obtained. Also, a graph showing an oscilloscope trace of the SHG signal for a powder having a particle size of 150 to 200 mu m was obtained.

3 is a graph showing the optical characteristics and nonlinear optical property evaluation results of the polar non-center-symmetrical borate-based crystals according to the present invention.

(B) shows the SHG intensity and the particle size of Pb ₂ BO ₃ Cl (20 to 45 nm). FIG. 3 (a) shows the absorption spectrum of ultraviolet- , 45 to 63, 63 to 75, 75 to 90, 90 to 125, 125 to 150, 150 to 200 and 200 to 250 μm) and an oscilloscope trajectory (inserted graph) of the SHG signal. and c) is a graph showing infrared transmittance according to wavelengths.

3 (a), it can be seen that no absorption takes place from 0.30 μm to 2.5 μm in ultraviolet-visible light because Pb ₂ BO ₃ Cl is a broad transparent region from the near-ultraviolet region to the mid-infrared region . The measured ultraviolet absorption edge of Pb ₂ BO ₃ Cl is substantially short compared to other lead-borate compounds, which results in a light halide that can effectively cause a blue-shift of the absorption edge This is due to the introduction of chlorine ions. The optical bandgap of Pb ₂ BO ₃ Cl is 3.99 eV.

FIG. 3 (b) is a graph showing the relationship between the time-SHG intensity and a small graph.

Referring to FIG. 3 (b), it can be seen that the SHG intensity varies with the particle size of Pb ₂ BO ₃ Cl. From 20 to 45 μm to 150 to 200 μm, the SHG intensity increases as the particle size increases Can be seen. In particular, it can be confirmed that Pb ₂ BO ₃ Cl according to the present invention exhibits a very large SHG response characteristic of about 9 times KDP. It is also seen that Pb ₂ BO ₃ Cl exhibits an SHG response characteristic of about six times that of KBBF. The graph between SHG intensity and particle size shown in Figure 3 (b) relates to the type I phase-matching behavior according to the law proposed by Kurtz and Perry.

Referring to FIG. 3 (c), it can be seen that the infrared spectrum has a band around 1,197 cm ^-1 and between 600 and 800 cm ^-1 . The peak appearing at around 1,197 cm ^-1 appears as a result of stretching vibration of BO, and it can be seen that it appears over a wide range. In addition, it can be seen that the bands appearing at between 600 and 800 cm ^-1 appear at 742 cm ^-1 , 728 cm ^-1 and 625 cm ^-1 because of the bending mode of the BO ₃ triangular unit and the stretching of Pb-O It is caused by vibration.

SEM / EDX analysis and results

Pb ₂ BO ₃ Cl was analyzed by SEM / EDX (scanning electron microscope / energy-dispersive analysis by X-ray). For this purpose, Hitachi S-3400N / Horiba Energy EX-250 device was used.

As a result, it was confirmed that the ratio of lead atom to chlorine atom in Pb ₂ BO ₃ Cl was 2.1: 1.0.

Structural Analysis-1

For Pb ₂ BO ₃ Cl, the density functional theory (DFT) calculation was performed using the TB-LMTO-ASA (Stuttgart TB-LMTO 47 program with the atomic sphere approximation) method. The results are shown in Fig.

4 is a graph showing the total state density and partial state density (partial DOS, PDOS) of the polar non-center-symmetrical borate-based crystals according to the present invention.

In Figure 4, (a) denotes a Pb ₂ BO ₃ Cl total state density (Total density of states, TDOS) of, (b) will represent a part of the state density of the _{Pb 2 BO 3 Cl (partial DOS} , PDOS) , Boron, oxygen, lead and chlorine atoms, respectively. The dotted line in the vertical direction indicates E _F as an energy reference (0 eV).

Referring to FIG. 4, the bandgap of Pb ₂ BO ₃ Cl is expected to be 2.32 eV, which is significantly smaller than the experimental result. It is well known in the literature that the electron band structure calculation using DFT tends to underestimate the gap energy. However, this band structure calculation is very helpful in locating important orbital interactions.

The TDOS graph shown in Figure 4 (a) shows the overall orbital mixing of the four elements over the entire energy range. The valence band (VB) region below the Fermi level (E _F ) can be divided into five small sections based on the atomic orbital distribution. In particular, the largest orbital distribution in the valence band region is the [BO ₃ ] ³ -moiety, which has a triangular planar shape, from which it is lowered. The lowest section (section 1), between -9.5 eV and -8.0 eV, consists of the s-state of the central boron (B) and the three states O) surrounded by the p _y group orbitals. The section (section 2) between -7.8 eV and -7 eV is mostly due to the p _x , p _y state of boron (B) and the p _y group orbitals of three oxygen (O) Lt; RTI ID = 0.0 > sigma-interaction. ≪ / RTI > In addition, oxygen (O), surrounded by a section (section 3) is the group orbitals, especially [BO _3] π- interaction of ^3-group of boron (B), and oxygen (O) between -7 to -4 eV eV , Due to the p _z state of all. The section between -3.5 eV and -1 eV (Section 4) is affected by the p _x , p _y states of boron (B) and the large p _x states of the group orbitals of oxygen (O) all of (Pb) and chloride (Cl) p And form almost nonbonding interactions with the states.

The section (Section 5) between -1 eV and Fermi level (E _F ) is mostly p It is affected by the state. Interestingly, the lead (Pb) and, according to PDOS analysis of chlorine (Cl), the state s of the lead (Pb) is contributing to the section 1 and section 2, and boron (B), and [BO _3] of the ^three-oxygen groups ( O) form sigma-interactions. Further, when p The state overlaps Section 3, and the p _z states of both boron (B) and oxygen (O) establish a pi-interaction in the [BO ₃ ] ³ -group.

Structural Analysis-2

For Pb ₂ BO ₃ Cl, an electron localized function (ELF) diagram showing the cross-section along the ab-plane was obtained. Also, an ELF diagram showing a cross section perpendicular to the b-axis direction was obtained, and an ELF diagram showing a cross section along KBBF [0 -1 1] was obtained. The results are shown in Fig.

FIG. 5 is a diagram showing a structural analysis result of a polar non-center-symmetrical borate-based crystal according to the present invention. FIG.

If in Fig. 5, (a) is a case of Z = 0 in the ab- surface, (b) is a case of Z = 0.112 in the ab- surface, (c) is of y = 0.137 in the b- axis direction, ( d) represents the case of y = 0.274 in the b-axis direction. 5 (e) is an ELF diagram of KBBF.

Referring to FIG. 5 (a), the atomic interactions within the [BO ₃ ] ³ group in the ab-plane and the interactions between the [BO ₃ ] ³ -group, lead (Pb) and ab- All of the chlorine (Cl) in the sample is clearly shown in the ELF diagram.

Referring to FIG. 5 (b) with reference to FIG. 5 (a), the [BO ₃ ] ^3- group in the ab-plane through the structure represented by the (0 0 1) section in the case of Z = 0 and Z = And lead (Pb) can be confirmed. In particular, in terms of _{(0 0 0.112) [BO 3} ] by the two-dimensional layer of the ^3-group and lead (Pb) is positioned, [BO _3] E from lead (Pb), toward the oxygen (O) of a ^three-group It can be seen that the densities appeared well. More interestingly, it can be seen that the interactions between the atoms between [BO ₃ ] ^3- group and lead (Pb) are very good even in the section perpendicular to the b-axis.

Referring to (c) of 5, [BO _3], the two oxygen (O) is in the plane y = 0.137 placed in a ^three-group, forming an extended two-dimensional layered [BO _3] ^3- group and Interaction between the atoms between lead (Pb) is evident. Also, as shown in the PDOS graph of FIG. 4 (b), the unconjugated states of oxygen (O) and the p state of lead (Pb) affecting section 4 of PDOS are represented by this kind of interaction.

Referring to Figure 5 (d), at another cross-section at y = 0.274 located midway between oxygen (O) and lead (Pb), lead (Pb) and It can be seen that the interatomic interaction clearly appears between chlorine (Cl).

As a result, the interconnection of the [BO ₃ ] ³ group via the lead ion (Pb ²⁺ ) in the ab-plane forms an extended two-dimensional layer as shown in FIG. 5 (c) . For comparison, KBFF was checked for the ELF diagram with a cross-section of (1 -1 0). As shown in Figure 5 (e), there is no specific interaction between potassium (K) and oxygen (O) It can be confirmed that the distance between the extended atoms is 4.036 Å.

Compared to the bond length between lead-oxygen and chlorine-oxygen in Pb ₂ BO ₃ Cl, the bond length between beryllium-oxygen in KBBF is 1.636 Å and the bond length between fluorine-oxygen is 2.596 Å, which is relatively short Nevertheless, it can be seen that there is practically no interaction between atoms between beryllium-oxygen and fluorine-oxygen.

Therefore, the overall network of components with polarity in Pb ₂ BO ₃ Cl crystals can add synergy to the SHG characteristics and make them very strong. The spatial density of the [BO ₃ ] ³ group in Pb ₂ BO ₃ Cl is 0.00742 (per unit volume). KBBF has a relatively small value compared to 0.00946 (per unit volume) The synergistic effect of the interaction between the electron pair and the chlorine ion and the SHG property with a very high p-π interaction between the [BO ₃ ] ³ group and the lead ion in the extended [Pb ₂ (BO ₃ )] ⁺ layer . ≪ / RTI >

Linear optical properties may determine through the reflectance distribution curve, Pb ₂ BO ₃ Cl crystals according to the invention have a strong anisotropy (anisotropy), n ₀ is n _e through than that greatly appears Pb ₂ BO ₃ Cl crystal is negative. It can be seen that this is a uniaxial negative crystal.

Since the birefringence characteristic (Δn) is relatively large at 0.164 nm at 0.12 nm, phase matching occurs well in the SHG process. Compared with KBBF and Pb ₂ BO ₃ Cl crystals, the enhanced birefringence properties of lead ions lead to strong electronic anisotropic polarity and high SHG efficiency, as confirmed by experimental results. Since the Pb ₂ BO ₃ Cl crystals belong to class 32 in the Kleinman symmetry rule, only the set of independent SHG tensor components ( d ₁₁ ) remains. The value of the calculated frequency-dependent SHG tensor component ( d ₁₁ ) of the Pb ₂ BO ₃ Cl crystal is 7.2 pm / V at 1,064 nm (1.165 eV).

As described above, the new NLO material, Pb ₂ BO ₃ Cl, is synthesized through a molecular engineering design approach. The NLO material exhibits a remarkably strong SHG response characteristic of about 9 times as compared with KDP which exhibits the largest SHG response characteristic among KBBF compounds. In addition, Pb ₂ BO ₃ Cl has a large nonlinear coefficient, suitable birefringence characteristics, and a wide transmittance window because Pb ₂ BO ₃ Cl has excellent potential as a high performance NLO material in photonic applications .

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the present invention as defined by the following claims. It can be understood that it is possible.

Claims (6)

Represented by the formula Pb ₂ BO ₃ Cl,
[Pb ₂ BO _3] includes [Pb ₂ BO _3] ⁺ layer containing an atomic group represented by the cation ^+,
As a crystal having a structure in which chlorine ions (Cl < ^- >) are arranged between [Pb ₂ BO ₃ ] ⁺ layers facing each other,
Characterized in that the ultraviolet-visible light absorption rate is 80% or more in a wavelength range of 500 nm to 2500 nm.
Polarity non-center-symmetric borate-based crystals.
The method according to claim 1,
The [Pb ₂ BO ₃ ] ⁺ layer consists of a BO ₃ triangular unit and a PbO ₃ triangular pyramid,
and the [Pb ₂ BO ₃ ] ⁺ layer in the ac plane has a honeycomb structure.
Polarity non-center-symmetric borate-based crystals.
3. The method of claim 2,
The BO ₃ triangular unit of the [Pb ₂ BO ₃ ] ⁺ layer shares its vertex with six PbO ₃ triangular pyramids.
Polarity non-center-symmetric borate-based crystals.
The method according to claim 1,
Characterized in that the crystal structure is a triangular polar non-center symmetric space group, P 321 (No. 150).
Polarity non-center-symmetric borate-based crystals.
delete Characterized in that the polar non-center-symmetrical borate-based crystals according to claim 1 are applied to any one of a laser device, a nonlinear optical device, a piezoelectric sensor, a radio communication, a catalyst, a power storage transport device, a computer element or a quantum interference device.
product.

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