JP7121337B2 - Glass material manufacturing method and glass material - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a glass material and the glass material.

A glass material containing terbium oxide (Tb ₂ O ₃ ), which is a paramagnetic compound, is known to exhibit the Faraday effect, which is one of the magneto-optical effects. The Faraday effect is the effect of rotating the plane of polarization of linearly polarized light passing through a material placed in a magnetic field. Such effects are utilized in optical isolators, magnetic field sensors, and the like.

The optical rotation (angle of rotation of the plane of polarization) θ due to the Faraday effect is expressed by the following formula (1), where H is the strength of the magnetic field and L is the length of the substance through which the polarized light passes. In Equation (1), V is a constant dependent on the type of substance and is called the Verdet constant. The Verdet constant has a positive value in the case of a diamagnetic material and a negative value in the case of a paramagnetic material. The greater the absolute value of the Verdet constant, the greater the absolute value of the optical rotation, resulting in a greater Faraday effect.

θ=VHL Formula (1)

For example, Patent Documents 1 and 2 disclose paramagnetic glass containing Tb ₂ O ₃ . In general, the more Tb ₂ O ₃ is contained, the larger the Verdet constant and the greater the Faraday effect.

The glass materials described in the above documents are produced by melting raw materials in a melting container such as a crucible and cooling them. However, this method has a problem that crystallization tends to progress starting from the contact interface with the melting vessel, and devitrification tends to occur. In particular, since Tb ₂ O ₃ is a component that hardly forms glass, crystallization easily progresses, and there is a problem that it is difficult to obtain a glass material.

Therefore, a method has been proposed for producing a glass material having a larger Verdet constant by containing more Tb ₂ O ₃ by using a method other than the melting method. For example, Patent Document 3 discloses a glass material containing more than 48% Tb ₂ O ₃ . In the above document, the glass material is manufactured by melting raw materials in a floating state and cooling them (containerless floating method). _In this method, the molten glass hardly comes into contact with the melting vessel _, and crystallization starting from the interface with the melting vessel can be prevented. A glass material can be obtained.

Japanese Patent Publication No. 51-46524 Japanese Patent Publication No. 52-32881 JP 2016-145143 A

By the way, the above-described containerless floating method includes a mixing step of mixing the raw material powders, an integration step of integrating the raw material powders to obtain a raw material lump, and heating and melting the raw material lump while holding the raw material lump in a floating state. and a cooling step of cooling the molten glass after the molten glass is obtained. In this method, unlike the method in which the raw material is melted in a melting vessel such as a crucible, the raw material cannot be stirred while the raw material lump is being melted in the melting process, and the composition of the obtained glass material varies. can be uneven. If the glass material becomes inhomogeneous, there is a problem that, for example, the Verdet constant tends to vary. In addition, devitrification occurs due to variations in composition, and devitrification tends to occur. Therefore, in order to homogenize the glass material, it is necessary to sufficiently mix the raw materials in advance before the melting process.

However, even when the raw materials are sufficiently mixed, there is a problem that devitrification occurs in the glass. When a magneto-optical element is manufactured using a glass material with devitrification, not only does the transparency decrease, but the devitrification may become a source of heat generation. There is a possibility that the function of the magneto-optical element may not be fulfilled.

In view of the above, an object of the present invention is to provide a method for producing a glass material that has high homogeneity and is less likely to cause devitrification, and the glass material.

The method for producing a glass material of the present invention includes a mixing step of mixing raw material powders, an integration step of integrating the raw material powders to obtain a raw material lump, and a melting step of heating and melting the raw material lumps while floating to obtain molten glass. and a cooling step of cooling the molten glass, wherein the raw material powder is mixed using a zirconia tool so that the content of ZrO ₂ in the glass material is 500 ppm or less. characterized by

According to the above configuration, since a tool made of zirconia having excellent wear resistance is used, the raw materials can be sufficiently mixed, and a glass material with high homogeneity can be obtained. By mixing the raw material powders so that the content of ZrO ₂ in the glass material is 500 ppm or less, generation of devitrified matter can be suppressed even when the raw materials are sufficiently mixed.

In the method for producing a glass material of the present invention, the glass material preferably contains more than 48% Tb ₂ O ₃ in terms of mol %.

In the method for producing a glass material of the present invention, the glass material preferably contains 80% or less of Tb ₂ O ₃ in terms of mol %.

In the method for producing a glass material of the present invention, the glass material further contains, in mol %, SiO ₂ 0 to 50%, B ₂ O ₃ 0 to 50%, Al ₂ O ₃ 0 to 50%, P ₂ O ₅ 0 to It preferably contains 50%. Since SiO ₂ , B ₂ O ₃ , Al ₂ O ₃ , and P ₂ O ₅ are components that constitute the glass skeleton, vitrification can be performed relatively easily by including these components.

In the method for producing a glass material of the present invention, it is preferable that the glass material is used as a Faraday element.

The glass material of the present invention is characterized by containing more than 48% Tb ₂ O ₃ and 0.1 to 500 ppm ZrO ₂ in mol %.

According to the above configuration, it is possible to obtain a glass material that has a high Verdet constant, high homogeneity, and is less susceptible to devitrification.

Advantageous Effects of Invention According to the present invention, it is possible to provide a method for producing a glass material that has high homogeneity and is less prone to devitrification, and the glass material.

1 is a schematic cross-sectional view showing one embodiment of an apparatus for manufacturing a glass material of the present invention; FIG.

Preferred embodiments are described below. However, the following embodiments are merely examples, and the present invention is not limited to the following embodiments. Also, in each drawing, members having substantially the same function may be referred to by the same reference numerals.

(Manufacturing method of glass material)
The method for producing a glass material of the present invention includes a mixing step of mixing raw material powders, an integration step of integrating the raw material powders to obtain a raw material lump, and a melting step of heating and melting the raw material lumps while floating to obtain molten glass. and a cooling step of cooling the molten glass.

The mixing step is a step of mixing raw material powders with a tool made of zirconia. Zirconia has excellent wear resistance and a large specific gravity compared to agate and alumina, so it is easy to mix the raw materials homogeneously, and the occurrence of devitrification due to variations in composition can be reduced. . A zirconia-made instrument in the present invention comprehensively means an instrument containing zirconia (ZrO ₂ ) as a main component. Therefore, a device made of an oxide (stabilized zirconia, partially stabilized zirconia) containing zirconia as a main component, in which an oxide such as yttria (Y ₂ O ₃ ) is introduced to stabilize the crystal structure of zirconia. good too. The zirconia tool is not particularly limited, but it is preferable to use a rotating container type (ball mill, etc.) or a fixed container type (rubbing machine, etc.). Alternatively, they may be mixed using a zirconia mortar or the like. When an agate instrument or an alumina instrument is used, there is a possibility that SiO ₂ and Al ₂ O ₃ may be mixed from the instrument during mixing, and these contaminants may become the core of devitrified substances. Since such contaminants are more likely to occur the lower the wear resistance is, it is preferable to use zirconia instruments that are excellent in wear resistance from this point of view as well.

In addition, in the mixing step, the raw material powders are preferably mixed so that the content of ZrO ₂ in the glass material is 500 ppm or less, 100 ppm or less, particularly 20 ppm or less. Since ZrO ₂ forms the core of devitrified substances in the glass material, devitrified substances are likely to occur when the content of ZrO ₂ increases. Such ZrO ₂ is mixed from the equipment when mixing the raw materials. _The content of ZrO2 can be controlled by adjusting the applied pressure to the mixing device, mixing speed and mixing time. For example, the higher the pressure applied to the mixing device, the higher the mixing speed, and the higher the mixing _time , the higher the content of ZrO2. Although the lower limit of the ZrO ₂ content in the glass material is not particularly limited, it is practically 0.1 ppm or more. Further, the applied pressure in the present invention indicates the pressure applied to grind the raw material powder when using a mortar. Note that ZrO ₂ may be mixed as an impurity in the raw material. In the present invention, it is adjusted to 500 ppm or less including ZrO ₂ mixed as an impurity.

In the method for producing a glass material of the present invention, the glass material contains 48% or more, preferably 49% or more, and particularly preferably 50% or more of Tb ₂ O ₃ in terms of mol %. If the content of Tb ₂ O ₃ is too small, the absolute value of the Verdet constant becomes small, making it difficult to obtain a sufficient Faraday effect. On the other hand, if the content of Tb ₂ O ₃ is too high, vitrification tends to be difficult, so it is preferably 80% or less, 75% or less, particularly 70% or less.

Although the content of trivalent oxides is specified for Tb, the content of oxides other than trivalent oxides is preferably within the above range when converted to trivalent oxides. .

The magnetic moment, which is the origin of the Verdet constant for Tb, is larger for Tb ³⁺ than for Tb ⁴⁺ . Therefore, the larger the proportion of Tb ³⁺ in the glass material, the larger the Faraday effect, which is preferable. Specifically, the ratio of Tb ³⁺ in the total Tb is preferably 50% or more, 60% or more, 70% or more, 80% or more, particularly 90% or more in terms of mol %. Incidentally, Tb ³⁺ has relatively little light absorption in the wavelength range of 400 to 1100 nm, whereas Tb ⁴⁺ has wide light absorption in the wavelength range of 400 to 1100 nm, which causes a decrease in light transmittance. Also from such a point of view, it is preferable that the proportion of Tb ³⁺ in the glass material is large. Specifically, the transmittance at a wavelength of 633 nm and an optical path length of 1 mm is preferably 50% or more, 60% or more, 70% or more, and particularly preferably 80% or more.

In the method for producing a glass material of the present invention, the glass material can contain various components shown below in addition to the components described above. In the following description of the content of each component, "%" means "mol %" unless otherwise specified.

SiO ₂ , B ₂ O ₃ and P ₂ O ₅ are components that form a glass skeleton and widen the vitrification range. However, since these components do not contribute to the improvement of the Verdet constant, if the content is too large, it becomes difficult to obtain a sufficient Faraday effect. Therefore, the contents of SiO ₂ , B ₂ O ₃ and P ₂ O ₅ are preferably 0-50%, 1-45%, particularly 2-40%, respectively. Also, the total amount of SiO ₂ and B ₂ O ₃ is preferably 0 to 52%, 15 to 51%, particularly 20 to 50%. The total amount of B ₂ O ₃ and P ₂ O ₅ is preferably 0-52%, 15-51%, especially 20-50%. The total amount of SiO ₂ , B ₂ O ₃ and P ₂ O ₅ is preferably 0-52%, 15-51%, especially 20-50%.

Al ₂ O ₃ is a component that forms a glass skeleton as an intermediate oxide and widens the vitrification range. However, since Al ₂ O ₃ does not contribute to the improvement of the Verdet constant, if its content is too large, it becomes difficult to obtain a sufficient Faraday effect. Therefore, the content of Al ₂ O ₃ is preferably 0-50%, 0.1-40%, 1-30%, 1-20%, especially 1-10%.

La ₂ O ₃ , Gd ₂ O ₃ , Yb ₂ O ₃ and Y ₂ O ₃ have the effect of stabilizing the glass, but if the content is too high, vitrification becomes rather difficult. Therefore, the content of La ₂ O ₃ , Gd ₂ O ₃ , Yb ₂ O ₃ and Y ₂ O ₃ is preferably 10% or less, particularly 5% or less.

Dy ₂ O ₃ , Eu ₂ O ₃ and Ce ₂ O ₃ stabilize the glass and also contribute to improving the Verdet constant. However, if the content is too large, vitrification becomes rather difficult. Therefore, the contents of Dy ₂ O ₃ , Eu ₂ O ₃ and Ce ₂ O ₃ are each preferably 15% or less, particularly 10% or less. In addition, although the content of trivalent oxides is specified for Dy, Eu, and Ce, the content of oxides other _than trivalent oxides (e.g., CeO2, etc.) is converted to trivalent oxides. Preferably the amount is within the above range.

MgO, CaO, SrO and BaO are effective in enhancing the stability and chemical durability of glass. However, since it does not contribute to the improvement of the Verdet constant, if the content is too large, it becomes difficult to obtain a sufficient Faraday effect. Therefore, the content of each of these components is preferably 0 to 10%, particularly preferably 0 to 5%.

Ga ₂ O ₃ has the effect of increasing the glass-forming ability and widening the vitrification range. However, if the content is too large, devitrification is likely to occur. Moreover, since Ga ₂ O ₃ does not contribute to the improvement of the Verdet constant, if its content is too large, it becomes difficult to obtain a sufficient Faraday effect. Therefore, the content of Ga ₂ O ₃ is preferably 0-6%, particularly 0-5%.

Fluorine has the effect of increasing the glass-forming ability and widening the vitrification range. However, if the content is too large, it may volatilize during melting and change the composition, affecting the stability of the glass. Therefore, the fluorine content (as converted to F2) is preferably ₀ to 10%, more preferably 0 to 7%, still more preferably 0 to 5%.

Sb ₂ O ₃ can be added as a reducing agent. However, in order to avoid coloration or consider the load on the environment, the content of Sb ₂ O ₃ is preferably 0.1% or less.

The integration step is a step of obtaining a raw material lump from the raw material powder. Here, the raw material lump is, for example, a material powder integrated by press molding or the like, a sintered body obtained by integrating the raw material powder by press molding or the like and then sintered, or a composition equivalent to the target glass composition. An aggregate of crystals having Moreover, you may use what cut|disconnected the said sintered compact as a raw material lump.

The melting step is a step of floating raw material lumps and heating and melting them to obtain molten glass. Moreover, a cooling process is a process of obtaining a glass material by cooling a molten glass. FIG. 1 is a schematic cross-sectional view showing an example of a manufacturing apparatus for manufacturing a glass material by the containerless floating method. A glass manufacturing apparatus 1 has a mold 10 . Mold 10 also serves as a melting vessel. The molding die 10 has a molding surface 10a and a plurality of gas ejection holes 10b opening in the molding surface 10a. The gas ejection hole 10b is connected to a gas supply mechanism 11 such as a gas cylinder. Gas is supplied from the gas supply mechanism 11 to the molding surface 10a through the gas ejection holes 10b. The type of gas is not particularly limited, and may be, for example, air or oxygen, nitrogen gas, argon gas, helium gas, carbon monoxide gas, carbon dioxide gas, or reducing gas containing hydrogen. good.

To manufacture a glass material using the manufacturing apparatus 1, first, the raw material lump 12 is arranged on the molding surface 10a. Next, the raw material mass 12 is made to float on the molding surface 10a by ejecting gas from the gas ejection holes 10b. That is, the raw material lump 12 is held without contacting the molding surface 10a. In this state, the raw material mass 12 is irradiated with laser light from the laser light irradiation device 13 . Thereby, the raw material lump 12 is heat-melted and vitrified to obtain molten glass. After that, the glass material can be obtained by cooling the molten glass.

In the melting process and the cooling process, it is preferable to continue blowing out gas at least to suppress contact between the raw material lump 12, the molten glass, and the glass material and the molding surface 10a. Instead of blowing out the gas, or by applying a magnetic field together with blowing out the gas, the generated magnetic force may be used to float the raw material lump 12 on the forming surface 10a. Moreover, as a method of heating and melting, radiation heating may be used in addition to the method of irradiating with a laser beam. In the cooling step, it is preferable to cool the glass material by continuously blowing gas until the temperature of the glass material becomes at least equal to or lower than the softening point.

The glass material produced by the present invention can be used for Faraday elements. It can also be used for magneto-optical elements such as a Faraday rotator using a Faraday element, an optical isolator using a Faraday rotator, and an optical circulator.

(glass material)
The glass material of the present invention is characterized by containing more than 48% Tb ₂ O ₃ and 0.1-500 ppm ZrO ₂ in mol %. The composition of the glass material of the present invention is as described above, and the description is omitted here.

In the glass material of the present invention, the content of ZrO ₂ is 500 ppm or less, preferably 100 ppm or less, particularly preferably 20 ppm or less. The lower the content of ZrO ₂ is, the better, but the lower limit is 0.1 ppm or more in consideration of mixing by zirconia equipment and impurities from raw materials. Attempting to reduce the amount of ZrO ₂ to less than 0.1 ppm results in insufficient mixing of the glass raw materials and excessive raw material costs.

EXAMPLES The present invention will be described below based on examples, but the present invention is not limited to these examples.

Tables 1 to 3 show examples of the present invention (samples 2 to 6, samples 9 to 13, samples 16 to 20) and comparative examples (samples 1, 7, 8, 14, 15, and 21). showing.

Each sample was produced as follows. Raw materials prepared to have the glass compositions shown in Tables 1 to 3 are manually mixed for 30 minutes using an agate mortar (mixing container A), or a YTZ (yttria-stabilized zirconia) mortar (mixing container B ) was used for 30 minutes to 1200 minutes and mixed with a mortar machine. _The content of ZrO2 was adjusted with the mixing time. The mixed raw materials were pressed to obtain 0.5 g pieces. The obtained small piece was sintered at 700 to 1400° C. for 6 hours to obtain a raw material ingot.

Next, a disk-shaped glass material (about 5 mm in diameter) was produced from the obtained raw material lump by a containerless floating method using an apparatus according to FIG. A 100 W CO ₂ laser oscillator was used as a heat source. Nitrogen gas was used as a gas for floating the raw material mass, and was supplied at a flow rate of 1 to 30 L/min. Twenty samples were prepared for each condition, and the variation in the Verdet constant and the probability of occurrence of devitrified matter were evaluated as described below.

The Verdet constant was measured using a Kerr effect measuring device (manufactured by JASCO Corporation, product number: K-250). Specifically, the obtained glass material was polished to a thickness of about 1 mm, the Faraday rotation angle was measured at a wavelength of 1060 to 1068 nm in a magnetic field of 15 kOe, and the Verdet constant at a wavelength of 1064 nm was calculated. The wavelength sweep speed was set to 2 nm/min. The variation width of the Verdet constant was calculated by subtracting the minimum value from the maximum value of the Verdet constant obtained by measuring each glass material. The results are shown in Tables 1-3.

The presence or absence of devitrified substances inside the glass material was confirmed using a stereoscopic microscope (manufactured by Nikon Corporation, product number: SMZ1000), and the probability of occurrence of devitrified substances was evaluated. When the probability of occurrence of devitrified matter is 0 to 30%: ◎, When the probability of occurrence of devitrified matter is 30 to 50%: ○, When the probability of occurrence of devitrified matter is 50 to 80%: △, Devitrification When the probability of occurrence of an object is 80 to 100%: x. The results are shown in Tables 1-3.

As is clear from Tables 1 to 3, the glass material mixed with the zirconia tool has a smaller variation width of the Verdet constant than the glass material mixed with the agate mortar. In addition, the glass material mixed in the agate mortar had a high probability of devitrification even though the mixing time was short. This is probably because the glass materials mixed in the agate mortar were not sufficiently mixed, and devitrified substances were generated due to variations in composition.

Moreover, as is clear from Tables 1 to 3, the glass materials with a ZrO ₂ content of 500 ppm or less had a probability of generating devitrified matter of 80% or less, and the devitrified matter was less likely to occur. On the other hand, in glass materials with a ZrO ₂ content of 500 ppm or more, the probability of occurrence of devitrification was as high as 80% or more.

The glass material of the present invention is suitable as a magneto-optical element that constitutes a magnetic device such as an optical isolator, an optical circulator, or a magnetic sensor.

REFERENCE SIGNS LIST 1 glass material manufacturing apparatus 10 mold 10a molding surface 10b gas ejection hole 11 gas supply mechanism 12 raw material mass 13 laser beam irradiation device

Claims (6)

A mixing step of mixing the raw material powders, an integrating step of integrating the raw material powders to obtain a raw material lump, a melting step of heating and melting the raw material lumps while floating to obtain molten glass, a cooling step of cooling the molten glass, A method for manufacturing a glass material comprising
The glass material contains, in mol %, more than 48% Tb ₂ O ₃ and a total of 15 to 51% SiO ₂ , B ₂ O ₃ and P ₂ O ₅ ,
A method for producing a glass material, characterized by mixing the raw material powders using a zirconia tool such that the content of ZrO ₂ in the glass material is 0.1 to 51 ppm. _3. The method for producing a glass material according to claim 1, wherein the glass material contains 80% or less of _Tb2O3 in terms of mol %. The glass material further contains 0 to 50% SiO ₂ , 0 to 50% B ₂ O ₃ , 0 to 50% Al ₂ O ₃ , and 0 to 50% P ₂ O ₅ in terms of mol %. 4. The method for producing a glass material according to claim 2 or 3. 5. The method for producing a glass material according to claim 1, wherein the glass material is used as a Faraday element. characterized by containing, in mole %, more than 48% Tb ₂ O ₃ , a total of 15-51% SiO ₂ , B ₂ O ₃ and P ₂ O ₅ , and 0.1-51 ppm ZrO ₂ , glass material. 6. The glass material according to claim 5, which is used as a Faraday element.

Images