KR100869664B1 - Glasses in the series of xK2O-14-xNa2O-14Nb2O5-72TeO2 - Google Patents

Abstract

The present invention relates to a transparent glass ceramic, and more particularly, has a second harmonic (SHG) characteristic that can be applied to a nonlinear optical material while having a low melting point, a high refractive index, a high dielectric constant, and an excellent infrared transmittance. A transparent xK ₂ O- (14-x) Na ₂ O-14Nb ₂ O ₅ -72 TeO ₂ -based crystallized glass.

In the present invention, each of the reagents of K ₂ CO ₃ , Na ₂ CO ₃ , Nb ₂ O ₅ , TeO ₂ is mixed in each component ratio, placed in a melting crucible, heated and melted, and then obtained by maintaining the molten solution on a prepared plate. This provides xK ₂ O- (14-x) Na ₂ O-14Nb ₂ O ₅ -72 TeO ₂ -based crystallized glass having x = 0 to 14 mol%.

Crystallized glass, TeO2 glass second harmonic, nonlinear optical material, laser, cubic crystal phase, face centered cubic structure, crystal structure distortion, K + ion

Description

Tellurium dioxide-based crystallized glass {Glasses in the series of xK2O- (14-x) Na2O-14Nb2O5-72TeO2}

1 is a graph showing a powder XRD diffraction pattern according to the temperature of 14Na ₂ O-14Nb ₂ O ₅ -72 TeO ₅ -based glass.

2 is a graph showing a powder XRD diffraction pattern according to the K ₂ O component ratio of xK ₂ O— (14-x) Na ₂ O-14Nb ₂ O ₅ -72 TeO ₂ -based crystallized glass according to an embodiment of the present invention.

3 is a high-resolution transmission electron microscope (HR-TEM) photograph of a transparent 10K ₂ O-4Na ₂ O-14Nb ₂ O ₅ -72 TeO ₂ crystallized glass according to an embodiment of the present invention.

4 is a graph showing the lattice constant change of the crystal phase in xK ₂ O— (14-x) Na ₂ O-14Nb ₂ O ₅ -72 TeO ₂ -based crystallized glass according to an embodiment of the present invention.

5 is a graph showing the change in SH intensity according to the incident angle of the transparent 10K ₂ O-4Na ₂ O-14Nb ₂ O ₅ -72 TeO ₂ crystallized glass according to an embodiment of the present invention.

6 is a view showing the change in SH strength according to the component ratio of the transparent xK ₂ O- (14-x) Na ₂ O-14Nb ₂ O ₅ -72 TeO ₂ -based crystallized glass according to an embodiment of the present invention.

The present invention relates to a transparent glass ceramic, and more particularly, has a second harmonic (SHG) characteristic that can be applied to a nonlinear optical material while having a low melting point, a high refractive index, a high dielectric constant, and an excellent infrared transmittance. A transparent xK ₂ O- (14-x) Na ₂ O-14Nb ₂ O ₅ -72 TeO ₂ -based crystallized glass.

Glass ceramics are considered to have a wide range of applications due to their compact structure, high heat resistance, mechanical strength, relatively high softening temperature and low thermal expansion rate. Such crystallized glass is usually opaque, but some of the transparent crystallized glass has already been reported.

Recently, the development of various applications using nonlinear optical phenomena such as lasers has been called for, and the second harmonic (SHG) characteristic becomes a very important problem. For example, a laser whose wavelength is divided in half using a second harmonic generating element is called a SHG laser, which is attracting attention as a light source of a next generation optical disk.

TeO ₂ based glass has been of scientific and technical interest due to its low melting point, high refractive index, high dielectric constant, and excellent infrared transmittance compared to conventional SiO 2 based glass. Thus, TeO ₂ -based glass is attracting attention as a promising material for the application of optical fibers and nonlinear optical devices. Moreover, the structure of TeO ₂ -based glasses is of particular interest because TeO ₂ -based glasses have two basic structures. One is TeO ₄ trigonal pepper (TeO ₄₎ with an isolated electron pair at the equator. trigonal bipyramid) and the other is TeO ₃ Trigonal Pepper (TeO ₃ trigonal bipyramid) structure.

Therefore, it is necessary to develop a material having a crystal structure that is physically and chemically stable and also has second harmonic (SHG) characteristics by using such TeO ₂ -based glass.

SUMMARY OF THE INVENTION The present invention is derived from the above-mentioned practical necessity, and an object of the present invention is to provide a transparent crystal structure using TeO ₂ -based glass, and at the same time, a novel crystallization having second harmonic properties to be applied to nonlinear optical materials or photocatalyst devices. To provide glass.

In order to achieve the above object, in the present invention, each reagent of K ₂ CO ₃ , Na ₂ CO ₃ , Nb ₂ O ₅ , and TeO ₂ is mixed at a component ratio of x: 14-x: 14: 72, After heating and melting for 30 minutes to 2 hours at a temperature of 800 ~ 1100 ℃ and holding the molten solution on the prepared plate obtained x x 1 O ₂ (14-x) Na ₂ O x = 1 ~ 14 mol% -14 Nb ₂ O ₅ -72 TeO ₂ -based crystallized glass.

Here, the molten liquid is preferably cooled on a metal plate or carbon plate heated to 200 to 350 ° C.

Hereinafter, with reference to the accompanying drawings will be described in more detail the technical spirit of the present invention.

Example

Crystalline glass of xK ₂ O- (14-x) Na ₂ O-14Nb ₂ O ₅ -72 TeO ₂ series having x = 0 to 14 mol% was manufactured using a conventional melt cooling method. Raw materials used are K ₂ CO ₃ (99.5%, Nacalai), Na ₂ CO ₃ (99.5%, Soekawa Chemicals), Nb ₂ O ₅ (99.9%, Soekawa Chemicals), TeO ₂ (99%, Soekawa Chemicals) The reagents were mixed with powders calculated by the component ratio of x: 14-x: 14: 72, respectively, and then put into a platinum crucible and heated by melting at 800 to 1100 ° C. for 30 minutes to 2 hours. The used amount of the reagent was basis weight at 15 g.

Subsequently, xK ₂ O- (14-x) Na ₂ O-14Nb ₂ O ₅ -72 TeO ₂ -based crystallized glass having a thickness of 0.1 to 2 cm was obtained by cooling the melt on a carbon plate heated to 250 ° C. In this experiment, the x was varied from 0 to 14 mol%.

How to measure

The glass state at room temperature and the crystal phase in the heat-treated glass specimens of the cooled glass specimens obtained above were examined by powder X-ray diffraction analysis (XRD) using CuK α (alpha) radiation at room temperature. The SH intensity of the crystallized glass was measured using an Nd: YAG laser with a fundamental wavelength of 1064 nm as a function of the angle of incidence of the incident radiation. The Maker fringe method was used for this purpose. The laser output was maintained in the range of 0.5-1 W and the irradiation time of the light was measured in the range of 1-230.

Result

FIG. 1 is a graph showing powder XRD diffraction patterns when x = 0 in the above example, that is, at room temperature and in a heat-treated state of a 14Na ₂ O-14Nb ₂ O ₅ -72 TeO ₂ glass specimen. In the graph, A is a glass specimen at room temperature, B is a glass specimen heat treated at 375 ° C. for 1 hour, C is a glass specimen heat treated at 450 ° C. for 1 hour, D is a glass specimen heat treated at 475 ° C. for 1 hour, E Denotes a glass specimen heat-treated at 490 ° C. for 1 hour. The crystal phase appearing in the glass specimen (B of graph) heat-treated at 375 ° C. for 1 hour has a face-centered cubic structure with lattice constant a = 0.545 nm. In the graph, the XRD pattern shows that the cubic crystal phase disappears above 470 ° C. The particle size of the glass specimens heat-treated at 375 ° C. for 1 hour was measured from the full width at half maximum (FWHM) of the X-ray diffraction peak using the Scherrer's equation below.

L = 0.9 λ / B cosθ (1)

In the above,

λ: wavelength of X-ray radiation (λ = 0.154 nm)

B: FWHM of the peak (radians) corrected instrumental broadening

θ: Bragg angle

 L: Particle size (nm)

The average size of the particles was measured at 38 nm and the glass specimens appeared to be optically transparent. However, the specimens heat-treated at 470 ° C were opaque. It was found that the cause of the transparency of the crystallized glass obtained by heat treatment at 400 ° C. was due to the size of particles smaller than visible light and the presence of a cubic crystal structure. Two steps of heat treatment were performed to further reduce the size of the particles while producing a more optically transparent material, i.e. heat treatment at 370 ° C. for 1 hour on 14Na ₂ O-14Nb ₂ O ₅ -72 TeO ₂ glass and then again. Heat treatment was performed at 400 ° C. for 1 hour. However, in the 14Na ₂ O-14Nb ₂ O ₅ -72 TeO ₂ crystallized glass obtained in this manner, no second harmonic (SHG) characteristic was found.

FIG. 2 is a graph showing a powder XRD diffraction pattern according to the K ₂ O component ratio of the heat treated xK ₂ O— (14-x) Na ₂ O-14Nb ₂ O ₅ -72 TeO ₂ based crystallized glass. In the graph, A is x = 0 mol%, B is x = 6 mol%, C is x = 8 mol%, D is x = 10 mol% and E is x = 14 mol%. Except for x = 0, the formation of face-centered cubic structure was observed in the remaining glass specimens, and no impurity phase was observed. These specimens were also optically transparent to the naked eye. The average particle size of the xK ₂ O- (14-x) Na ₂ O-14Nb ₂ O ₅ -72 TeO ₂ based crystallized glass was measured to be 40 nm. One of the main features of the present invention was the acquisition of a transparent K ₂ O—Na ₂ O—Nb ₂ O ₅ —TeO ₂ based crystallized glass comprising a cubic crystal phase of about 35-40 nm in diameter. The refractive index of the K ₂ O—Na ₂ O—Nb ₂ O ₅ —TeO ₂ system crystallized glass was measured to be 2.07 ± 0.03. As with other transparent crystallized glasses, it was confirmed that the cause of the transparency of the K ₂ O—Na ₂ O—Nb ₂ O ₅ —TeO ₂ based crystallized glass is due to the size of particles smaller than the wavelength of visible light.

3 is a high-resolution transmission electron microscope (HR-TEM) photograph of 10K ₂ O-4Na ₂ O-14Nb ₂ O ₅ -72 TeO ₂ -based crystallized glass. The crystallized glass is composed of nanoparticles that form agglomerates that are 35 nm in size. It can be seen that the size of the crystallized glass particles measured from the XRD analysis is 40 nm, which is similar to the size of 35 nm, the size of the crystallized glass particles measured from the HR-TEM analysis.

Figure 4 shows the change of the lattice constant of the cubic phase in the glass with the change in mol% of K ₂ O. It can be seen that the lattice constant increases as the ratio of K + ions to the sum of K + ions and Na + ions increases. This phenomenon occurs because K + ions are obtained because the ion radius of K + ions (eg 0.151 nm in coordination number 4) is much larger than the ion radius of Na + ions (eg 0.113 nm in coordination number 4). It means that it is a component on the cubic.

Figure 5 shows the change in the SH strength of the transparent 10K ₂ O-4Na ₂ O-14Nb ₂ O ₅ -72 TeO ₂ crystallized glass with the angle of incidence and the angle of incidence in which SHG occurs in the crystallized glass.

Figure 6 shows the change in SH strength according to the component ratio of the transparent xK ₂ O- (14-x) Na ₂ O-14Nb ₂ O ₅ -72 TeO ₂ -based crystallized glass. It can be seen that the crystal of cubic phase showing SH characteristics is formed at x = 8 mol% or more.

As described above, in the case of K ₂ O—Na ₂ O—Nb ₂ O ₅ —TeO ₂ based crystallized glass according to the embodiment of the present invention, it is characterized by transparent and second harmonic characteristics. That is, the crystalline glass obtained according to the present invention has a low melting point, a high refractive index, a high dielectric constant, and an excellent infrared ray transmittance, so that the crystalline glass is excellent in physical properties and transparent, and thus it is considered to be applicable to various optical devices. In addition, using the second harmonic (SHG) characteristics of the transparent crystalline glass of the present invention will be possible to a variety of applications, such as nonlinear optical materials, photocatalyst devices.

Claims (3)

Reagents of K ₂ CO ₃ , Na ₂ CO ₃ , Nb ₂ O ₅ , and TeO ₂ were mixed at the component ratio of x: 14-x: 14: 72, respectively, and then placed in a melting crucible for 30 minutes at a temperature of 800 to 1100 ° C. Obtained by heating and melting for 2 to 2 hours and then holding the molten solution on a prepared plate, crystallization of xK ₂ O- (14-x) Na ₂ O-14Nb ₂ O ₅ -72 TeO ₂ based on x = 1-14 mol% Glass. The method of claim 1, An xK ₂ O- (14-x) Na ₂ O-14Nb ₂ O ₅ -72 TeO ₂ -based crystallized glass, which is obtained by cooling the melt on a metal plate or a carbon plate heated to 200 to 350 ° C. delete

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