WO2007114318A1

WO2007114318A1 - Process for producing vanadate glass

Info

Publication number: WO2007114318A1
Application number: PCT/JP2007/057035
Authority: WO
Inventors: Tetsuaki Nishida
Original assignee: Kitakyushu Foundation For The Advancement Of Industry, Science And Technology
Priority date: 2006-03-31
Filing date: 2007-03-30
Publication date: 2007-10-11
Also published as: JP5164072B2; JPWO2007114318A1

Abstract

A process for producing a vanadate glass, in which a striking increase of electric conductivity can be attained only by holding within a given temperature region for a short time, thereby enabling production of a vanadate glass with a high electric conductivity of 10-1 S-cm-1 or greater at room temperature, and in which even when the holding time in a given temperature region is varied, a variation of electric conductivity is slight to thereby ensure marked excellence in production stability and quality stability, and in which the magnitude of electric conductivity at room temperature can be designed and controlled with high precision within the region of 10-4 S-cm-1 or greater to thereby attain an increase of product yield. There is provided a process for producing a vanadate glass containing vanadium as a main component or an accessory component, comprising the vitrification step of vitrifying a composition containing vanadium to thereby obtain an oxide glass and the reheating step of holding the oxide glass at a temperature within the region exceeding the crystallization temperature of the oxide glass but not exceeding the melting point thereof for a given period of time.

Description

Specification

Manufacturing method of vanadate glass

Technical field

The present invention relates to a method for producing vanadate glass that is suitably used as an electrode material or the like.

Background art

[0002] Conventionally, vanadate glass containing vanadium as a main component or a subcomponent has been developed as a glass semiconductor used as a thermistor or the like. Vanadate glass is composed of vanadium oxide, diphosphorus pentoxide, alkali metal oxides such as potassium oxide and sodium oxide, alkaline earth oxides such as barium oxide, cerium oxide, tin oxide, lead oxide. It is known that the glass is made by calcining copper oxide. Vanadate glass, unlike ordinary ion-conducting acid-based glass, exhibits electronic conductivity, and thus has a relatively high electrical conductivity. However, vanadate glass, acid vanadium, diphosphorus pentoxide, than was produced glass in a conventional manner of quenching a melt of such alkaline earth Sani匕物did only be obtained as an electric conductivity of 10 ^_5 S 'cm one ¹ about at room temperature. Therefore, vanadate glass has not been applied to specific applications such as thermistor heaters.

Therefore, the present inventor aims to improve the electrical conductivity of the vanadate glass at room temperature by heating and melting the mixture containing acid vanadium and then rapidly cooling to obtain a glass composition. Developed a patent application for a method for producing a vanadate glass that is kept for a predetermined time at an annealing temperature not lower than the glass transition temperature and not higher than the crystallization temperature (Patent Document 1).

Patent Document 1: Japanese Patent Laid-Open No. 2003-34548

Disclosure of the invention

Problems to be solved by the invention

However, the invention described in Japanese Patent Application Laid-Open No. 2003-34548 (Patent Document 1) still has room for improvement in the following points.

(1) Electricity at room temperature of the vanadate glass produced by the technique disclosed in (Patent Document 1) Since the air conductivity was about 10 ^_4 to 10 ^_1 S 'cm ^_1 , vanadate glass having a high electrical conductivity of 10 ^_1 S' cm— ¹ or more is required to expand the application to electrode materials. It was.

(2) Since the electrical conductivity of the vanadate glass may vary depending on the holding time at the annealing temperature, production with little fluctuation in the electrical conductivity even if the holding time at the annealing temperature varies. There has been a demand for vanadate glass with excellent stability.

(3) In order to increase the production stability of the vanadate glass with high electrical conductivity and increase the product yield, the electrical conductivity of the vanadate glass is accurately designed in the region of 10 ^_4 S 'cm ^_1 or more. The technology to control is required!

[0004] The present invention has to satisfy the above requirements, it is possible to produce vanadate glass having a 10 ^{_ 1} S 'cm ^_1 more high electrical conductivity at room temperature, about 30 minutes at a predetermined temperature region Even if it is held for a short time, the electrical conductivity can be drastically increased, and even if the holding time in the specified temperature range fluctuates, there is little fluctuation in the electrical conductivity, resulting in production stability and quality stability. A manufacturing method of vanadate glass that can remarkably improve the electrical conductivity at room temperature and accurately control and control the magnitude of electrical conductivity in the region of 10 ^_4 S'cm—1 or higher, and increase the product yield. The purpose is to provide.

Means for solving the problem

[0005] In order to solve the above-described conventional problems, the method for producing vanadate glass of the present invention has the following configuration.

The method for producing a vanadate glass according to claim 1 of the present invention is a method for producing a vanadate glass containing vanadium as a main component or a subcomponent, wherein the composition containing vanadium is vitrified and acidified. A vitrification step for producing a glass product, and a reheating step for holding the oxide glass in a temperature range exceeding the crystallization temperature of the oxide glass and below a melting point for a predetermined time. ing.

With this configuration, the following effects can be obtained.

(1) Since there is a reheating process that holds the acid glass in the temperature range above the crystallization temperature of the acid glass and below the melting point for a predetermined time, the electrons in the acid glass are The energy High! It is possible to produce vanadate glass with a high electrical conductivity of 10 ^_1 S · cm— ¹ or more at room temperature, distributed in levels, and in a predetermined temperature range for about 30 minutes. Even if it is held for a long time, the electrical conductivity can be drastically increased, and even if the holding time in the specified temperature range fluctuates, the fluctuation of the electric conductivity is small and the production stability is remarkably excellent.

(2) By changing the heating time and holding time in the reheating process, the electrical conductivity of the vanadate glass at room temperature is designed and controlled accurately in the region of 10 ^_4 S'cm— ¹ or more. Product yield can be increased.

Here, as vanadate glass, one or more of vanadium, alkali metals such as potassium and sodium, alkaline earth metals such as barium and magnesium, cerium, tin, lead, copper and iron are used. A known glass having a kind of constituent atoms is used. Vanadate glass, which is a glass semiconductor, exhibits electrical conductivity when electrons hop between transition metal ions such as vanadium and iron.

In the reheating process of the present invention, the oxide glass is held in a temperature range higher than the crystallization temperature and lower than the melting point, whereas in the annealing process of Japanese Patent Laid-Open No. 2003-34548 (Patent Document 1), an acid treatment is performed. Since the glass of the glass is kept at the glass transition temperature or more and the crystallization temperature or less, the heat energy given to the acid glass in the reheating process of the present invention is the case of the annealing treatment of (Patent Document 1). Greater than the heat energy given to the acid glass. Therefore, the electrons in the oxide glass are distributed in a high energy level, and the thermal energy (activation energy) required to hop the electrons is smaller than in (Patent Document 1). We can guess that we can increase the electrical conductivity. Also, in the reheating process, by holding for a predetermined time at a temperature higher than the crystallization temperature of the oxide glass, the activation energy (electron hobbing) is removed by removing the distortion of the glass skeleton as in (Patent Document 1). Since the band gap can be reduced, it is assumed that the electrical conductivity can be increased as a result.

When the vanadate glass crystal is insulative, the electrical conductivity decreases when the vanadate glass crystallizes. Therefore, if it is kept for a long time at a temperature higher than the crystallization temperature of the oxide glass in the reheating process, insulating crystals will precipitate and the electrical conductivity will gradually increase. It will drop to. Therefore, in the reheating step, it is necessary to cool to below the crystallization temperature before the vanadate glass crystals are precipitated and the electrical conductivity is lowered.

[0007] The crystallization temperature and melting point can be determined by actually measuring an oxide glass by differential thermal analysis (DTA), differential scanning calorimetry (DSC), or the like. It can also be obtained by performing a thermodynamic calculation using the estimated component phase diagram.

When the crystallization temperature is determined by differential thermal analysis (DTA), the temperature at the center point of the exothermic peak of crystallization or the temperature at the high-side station temperature is used as the crystallization temperature. When the melting point is determined by differential thermal analysis (DTA), the temperature at the center point of the endothermic peak above the crystallization temperature is taken as the melting point.

[0008] As a means for vitrifying the composition in the vitrification step, a composition such as a mixture of crystalline solids is changed to a liquid or a gas, and then is crystallized without being crystallized. There is no particular limitation as long as the glass can be made. For example, an oxide glass can be obtained by heating and melting a composition such as a mixture of crystalline solids and then rapidly cooling the composition. Alternatively, an oxide glass can be obtained by once vaporizing a composition such as a mixture of crystalline solids by vapor deposition, sputtering, glow discharge, or the like. Further, an oxide glass can also be obtained by passing through a gel such as a sol-gel method.

[0009] In the reheating step of the acid glass, as a means for maintaining the temperature range above the crystallization temperature and below the melting point, for example, an electric furnace or the like is set to the reheating temperature in advance. When the temperature inside the furnace becomes constant, the oxide glass is put into the furnace, and when the target time has elapsed, the oxide glass is taken out from the electric furnace, etc., and a fluid such as air, water, ice water, Cooled copper plates or stainless steel plates, or those cooled by members such as copper or stainless steel rollers are used. Alternatively, after reheating the above-mentioned acid glass in a furnace such as an electric furnace for a certain period of time, the temperature in the furnace is gradually decreased or the temperature of the heating source in the furnace is gradually moved away from the acid glass. The one that is allowed to cool in the furnace is used. The inside of the furnace for reheating can be an atmosphere of inert gas such as air, nitrogen or argon.

[0010] The holding time in the reheating step can be appropriately set to an optimal time so that the electric conductivity of the oxide glass that has undergone the reheating step is increased. The holding time varies depending on the composition of oxide glass, heat capacity, and reheating temperature, but is set to 1 to 180 minutes, for example. . When the holding time is shorter than 1 minute, the thermal energy given to the oxide glass is small, so the rate of increase in electrical conductivity is small and the rate of increase is uneven. Since the electrical conductivity may decrease due to precipitation or melting, and the productivity decreases, the deviation is also preferable.

[0011] When the heating temperature in the reheating step is equal to or lower than the crystallization temperature of the acid glass, the thermal energy given to the acid glass is small, so the increase rate of the electrical conductivity is small and the increase rate is also low. When the heating temperature is equal to or higher than the melting point of the acid glass, the melting of the acid glass or the precipitation of crystals is promoted, and the electrical conductivity is lowered.

[0012] The electrical conductivity of an oxide glass (vanadate glass) at room temperature of 25 ° C is, for example, after a silver paste is applied to a sample made of a glass piece having a thickness of 1 mm or less, and then dried. The electrode can be formed by using the DC two-terminal method or the DC four-terminal method.

[0013] Electrical conductivity at 25 ° C of the thus re-heating step before the oxide glass obtained (vanadate glass) ^{^{is, 10 _8 ~10 _4 S 'cm}} _1 preferably 10 ^_6 to 10 ^_4 S It is preferably in the range of ' ^cm_1 . As the electrical conductivity becomes lower than 10 ^_6 S 'cm— ¹ , even after the reheating process, it tends to be difficult to improve the electrical conductivity to the practical level. From 10 0 ^_8 S' cm ^{_ 1} Lowering this is not preferable because this tendency becomes remarkable. Increasing the electrical conductivity of the oxide glass before the reheating process to more than 10 ^_4 S 'cm- ¹ is limited by the composition of the glass oxide and the temperature history of the vitrification process. At the same time, production stability is lacking.

Electrical conductivity of the oxide glass which has passed through the reheating step (vanadate glass) are 'is cm- ¹ preferably 10 one ³ ~ lS' 10 one ⁴ ~ lS at room temperature for 25 ° C in the range of cm- ¹ It can be improved. As the electrical conductivity becomes smaller than 10 ^_3 S 'cm ^{_ 1} , when vanadate glass is applied to the thermistor and heating element, power consumption increases and there is a tendency to lack energy savings. When applied to an electrostatic breakdown prevention member, the antistatic effect tends to decrease, and when applied to a plasma discharge electrode, it tends to be difficult to discharge. Especially when the electrical conductivity is less than 10 ^_4 S 'cm ^_1 This is not preferable because the tendency of

[0014] It should be noted that vanadate glass is composed of additives such as Agl, Nal, Ag, Ag 0, In 2 O, SnO, and SnO.

2 2 3 2 Additives may be added. It is also the power that can increase electrical conductivity by the effect of additives. Moreover, in addition to Agl, Nal, Ag, etc., a reduction inhibitor such as CeO can be added.

2

Good. This prevents the additives such as Agl, Nal, and Ag from being reduced and maintains high electrical conductivity.

[0015] The invention according to claim 2 of the present invention is the method for producing the vanadate glass according to claim 1, wherein the composition contains vanadium, barium and iron. Yes.

As a result, in addition to the action obtained in claim 1, the following action is obtained.

(1) A glass skeleton in which atoms of vanadium, barium, and iron are three-dimensionally related can be formed, and high electrical conductivity by electron hopping can be expressed.

(2) Since tetravalent and pentavalent vanadium and trivalent iron can be arranged in the glass skeleton, the probability of electron hopping is increased and the electrical conductivity can be increased.

[0016] Here, barium oxide (BaO), acid vanadium (V O), acid iron iron (F

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The ratio of e O) is special if an oxide glass that exhibits a glass transition phenomenon is obtained.

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In particular, the molar ratio (B: V) of barium oxide (B) to vanadium oxide (V) in the oxide glass is preferably 5:90 to 35:50. Better!/,.

Thereby, the following actions are obtained.

(1) Since a three-dimensional glass skeleton with vanadium as the main skeleton can be formed in the vitrification step, the electrical conductivity can be dramatically increased in the reheating step.

(2) The electrical conductivity of the oxide glass before the reheating process is reduced, and it is difficult to crystallize during the reheating process. The conductivity can be kept within a predetermined range, and the production stability is excellent.

Here, when the molar ratio (B: V) is smaller than 5:90, it becomes difficult to form a glass skeleton having a three-dimensional structure, and it becomes difficult to obtain a homogeneous oxide glass. When B: V) is larger than 35:50, vitrification becomes difficult, and crystallization tends to occur in the reheating step, and good conductivity is not exhibited. [0017] The molar ratio (F: V) of iron oxide (F) to vanadium oxide (V) in the oxide glass is preferably 5:90 to 15:50.

Thereby, the following actions are obtained.

(2) Since optical properties such as light transmittance are maintained to some extent, it can be used as an optical element by forming a thin film or fiber.

Here, when the molar ratio (F: V) is smaller than 5:90, it becomes difficult to vitrify, and when the molar ratio (F: V) is larger than 15:50, the optical properties such as light transmittance are deteriorated and homogeneous. It is difficult to obtain an acidic soda glass.

[0018] In addition, vanadium oxide (V O), barium oxide (BaO), iron oxide (Fe

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O) vanadium oxide in the three-component system of (VO) is from 40 to 98 mole ^_0/0 preferably 60

2 3 2 5

85 mol% is preferred. As it becomes less than 60 mol%, it tends to be difficult to maintain a glass skeleton with vanadium as the main skeleton, and it becomes difficult to obtain high electrical conductivity. In particular, since the content of subcomponents is reduced, adjustment functions such as electrical conductivity and mechanical properties due to the subcomponents tend to be reduced. In particular, if the amount is less than 40 mol% or more than 98%, these tendencies are remarkable, which is not preferable.

The barium oxide (BaO) in the above three-component system in the oxide glass is 1 to 40 mol%, preferably 10 to 30 mol%. When the amount is less than 10 mol%, homogenous vitrification tends to be difficult, and when the amount is more than 30 mol%, the mechanical strength decreases and the glass tends to become difficult to form. In particular, when the force is less than 1 mol% and the amount is more than 40 mol%, these tendencies tend to be remarkable, and therefore the deviation is also preferable.

Acid iron iron (Fe 2 O 3) in the above three-component system in the acid glass is preferably 1 to 20 mol%

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Is preferably 5 to 20 mol%. As the content becomes less than 5 mol%, the contribution of iron valence electrons to electron hopping tends to be reduced, and the electrical conductivity tends to be difficult to improve. On the other hand, if it exceeds 20 mol%, the optical properties such as light transmission properties are greatly deteriorated. In particular, the molar ratio of vanadium oxide (VO), barium oxide (BaO), and iron oxide (FeO) is

2 5 2 3

, Respectively 60 to 85 Monore ^_0/0, 10-30 Monore ^_0/0, to be in the range of 5 to 20 Monore ^_0/0, by reheating the Sani匕物glass, the number of electrical conductivity at room temperature It can be increased by 10 digits or more to 10 ⁻¹ S ′ cm− ¹ or more, and the thermistor can exhibit excellent characteristics as a heating element, various electrode materials, antistatic materials and the like.

[0019] The invention according to claim 3 of the present invention is the method for producing the vanadate glass according to claim 1 or 2, wherein the composition contains acid vanadium, barium oxide and iron oxide. The acid-containing glass has a configuration obtained by heating and melting the mixture and then rapidly cooling the mixture.

With this configuration, in addition to the effects obtained in claim 1 or 2, the following actions can be obtained.

(1) Since a mixture containing vanadium oxide, barium oxide and iron oxide is heated and melted and then rapidly cooled to obtain an oxide glass, it can be mass-produced at low cost and has excellent productivity.

[0020] Here, as vanadium oxide, vanadium monoxide (VO), divanadium trioxide (V

O), vanadium dioxide (VO), divanadium pentoxide (V

3 2 2 o) etc. can be used

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In particular, divanadium pentoxide (V o) is preferably used. Barium oxide

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This is because a three-dimensional glass skeleton is easily formed.

Examples of barium oxide include barium oxide (BaO), solid solution barium oxide containing excess oxygen, barium peroxide, and the like, but barium oxide (BaO) is generally used. In addition, when barium carbonate, barium oxalate, or the like is used, it decomposes by heating and melts, and BaO remains in the oxide glass, acting as network modifying ions.

Examples of iron oxides include iron monoxide (FeO), ferric trioxide (Fe 2 O), and triiron tetraoxide (Fe 2 O).

2 3 3 4 is used.

[0021] In addition to oxide vanadium, barium oxide, and iron oxide, rhenium oxide (R eO), silver (Ag), and the like can be added as the second component. This further improves electrical conductivity

Three

be able to. The amount of the second component such as oxyrhenium added is preferably 15 parts by mass or less with respect to 100 parts by mass of the mixture. If the added amount of the second component exceeds 15 parts by mass, the glass skeleton having vanadium as the main skeleton cannot be formed. The invention's effect

As described above, according to the method for producing vanadate glass of the present invention, the following advantageous effects can be obtained.

According to the invention of claim 1,

(1) Since it has a reheating step of holding the oxide glass having a glass transition temperature or lower for a predetermined time in a temperature range higher than the crystallization temperature of the oxide glass and lower than the melting point of the oxide glass. In addition to producing vanadate glass with a high electrical conductivity of 10 ^_1 S'cm— ¹ or more, the electrical conductivity can be drastically improved even if it is kept in the specified temperature range for a short time of about 30 minutes. In addition, it is possible to provide a method for producing a vanadate glass that has little fluctuation in electric conductivity even when the holding time in a predetermined temperature range fluctuates and is extremely excellent in production stability.

(2) By changing the heating time and holding time in the reheating process, the electrical conductivity of the vanadate glass at room temperature is designed and controlled accurately in the region of 10 ^_4 S'cm— ¹ or more. It is possible to provide a method for producing a vanadate glass capable of increasing the product yield.

[0023] According to the invention of claim 2, in addition to the effect of claim 1,

(1) A method for producing a vanadate glass capable of forming a glass skeleton in which atoms of vanadium, barium, and iron are three-dimensionally related and exhibiting high electrical conductivity by electron hopping can be provided. .

(2) Since tetravalent and pentavalent vanadium and trivalent iron can be arranged in the glass skeleton, it is possible to provide a method for producing a vanadate glass capable of increasing the probability of electron hopping and exhibiting high electrical conductivity.

[0024] According to the invention of claim 3, in addition to the effect of claim 1 or 2,

• Since a mixture containing vanadium oxide, barium oxide and iron oxide is heated and melted and then rapidly cooled to obtain an acid-containing glass, it provides a method for producing vanadate glass that can be mass-produced at low cost and has excellent productivity. it can.

Brief Description of Drawings

[0025] [Fig. 1] Differential thermal analysis results of acidified glass of Experimental Examples 1 to 3 [Fig. 2] A plot of the electrical conductivity before and after reheating of the acid glass of Experimental Examples 1 to 3 cooled below the glass transition temperature

[Fig. 3] Diagram showing the relationship between reheating temperature, reheating time and electrical conductivity of the oxide glass of Experimental Example 2

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be specifically described with reference to examples. The present invention is not limited to these examples.

(Experiment 1)

Barium oxide (BaO) is 10 mole ^_0/0, vanadium pentoxide (VO) force 0 mole ^_0/0, triacid

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Weigh each reagent grade reagent so that the total amount is 10 g and the total amount is 10 g.

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After mixing in an agate mortar, the mixture was placed in a platinum crucible, and the mixture in the platinum crucible was melted by heating in the air for 90 minutes in an electric furnace heated to 1000 ° C. The melt was poured onto a stainless steel plate having a thickness of 10 mm and quenched to below the glass transition temperature, whereby the oxide glass of Experimental Example 1 was obtained.

(Experiment 2)

Barium oxide (BaO) is 20 mole ^_0/0, vanadium pentoxide (VO) force 70 mole ^_0/0, triacid

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Weigh each reagent grade reagent so that the total amount of diiron ferrous (Fe 2 O 3) is 10 mol% and 10 g.

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Except that, the acid oxide glass of Experimental Example 2 was obtained in the same manner as Experimental Example 1.

(Experiment 3)

Barium oxide (BaO) is 30 mole ^_0/0, vanadium pentoxide (VO) force 0 mole ^_0/0, triacid

twenty five

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Except that, the acid oxide glass of Experimental Example 3 was obtained in the same manner as Experimental Example 1.

[0027] (Results of differential thermal analysis of oxide glasses of Experimental Examples 1 to 3)

Differential thermal analysis (DTA) of the oxide glasses of Experimental Examples 1 to 3 was performed. The differential thermal analysis (DTA) conditions are as follows: ex alumina is used as the reference material, and the temperature rise rate is 10 ° CZ in a nitrogen atmosphere.

FIG. 1 shows the results of differential thermal analysis of the oxide glasses of Experimental Examples 1 to 3.

From Figure 1, the molar ratio of barium oxide increases and the molar ratio of divanadium pentoxide decreases. As the glass transition temperature (Tg) and crystallization temperature (Tc) increased, the crystallization temperature Tc was 362 ° C in Experimental Example 1, 392 ° C in Experimental Example 2, and 433 ° C in Experimental Example 3. there were. The sharp endothermic peak seen in the temperature range above the crystallization temperature (Tc) shows the melting point, which is 600 ° C or higher in Experimental Example 1, 540 ° C in Experimental Example 2, and 540 ° C in Experimental Example 3. It was 563 ° C.

(Relationship between reheating temperature and electrical conductivity)

Experimental examples cooled to glass transition temperature or lower Re-heated 1 to 3 acidic glass in air at 350 ° C, 400 ° C, 500 ° C, and 550 ° C for 1 hour. The electrical conductivity of the front and rear oxide glasses at 25 ° C was measured by the DC four-terminal method.

Figure 2 is a plot of the electrical conductivity before and after reheating of the acid glass of Experimental Examples 1 to 3 cooled to below the glass transition temperature. In Fig. 2, the horizontal axis represents the reheating temperature (° C), and the vertical axis represents the electrical conductivity σ (S, cm– ¹ ) at 25 ° C.

From Fig. 2, when the oxide glass of Experimental Example 1 is reheated for 1 hour at 500 to 550 ° C, which is the temperature above the crystallization temperature (362 ° C) and below the melting point (600 ° C or higher). The electrical conductivity at 25 ° C was increased by about 4 orders of magnitude compared to before reheating.

In Fig. 2, the electrical conductivity when reheated at 400 ° C for 1 hour was the same as before reheating, but by reheating at 400 ° C for 2 hours, it was at room temperature (25 ° C). The electrical conductivity could be about 10 ^_3 S'cm ^_1 . In the oxide glass of Experimental Example 1, the holding time when the reheating temperature is 400 ° C is considered to be short in 1 hour.

Also, from Fig. 2, when the acidic glass of Experimental Example 2 is reheated for 1 hour at 400 to 500 ° C, which is the temperature above the crystallization temperature (392 ° C) and below the melting point (540 ° C). The electrical conductivity at 25 ° C was higher than 10 ^_3 S 'cm— ¹ . In particular, when reheated at 500 ° C, a high electrical conductivity of 10 ^_1 S 'cm- ¹ or higher was achieved. When reheated at 550 ° C, which is higher than the melting point (540 ° C) for 1 hour, part of it crystallized.

Also, from Fig. 2, when the oxide glass of Experimental Example 3 is reheated at 500 ° C, which is higher than the crystallization temperature (433 ° C) and lower than the melting point (563 ° C), 25 ° C The electrical conductivity of the material was 10 ^_2 S • cm— ¹ or higher.

When reheated at 550 ° C, which is close to the melting point (563 ° C) for 1 hour, part of it crystallizes. Therefore, the electrical conductivity of the oxide glass reheated at 550 ° C is plotted! /, Not! /. This is probably because the molar ratio of barium oxide to nivanadium pentoxide was increased. By shortening the holding time and reheating at 550 ° C for 0.5 hours, the electrical conductivity at 25 ° C was reduced to about 10 ^_2 S · cm– ¹ without crystallization.

Based on the above, the electrical conductivity at room temperature (25 ° C) is obtained through a reheating process in which the oxide glass (vanadate glass) is maintained in a temperature range exceeding the crystallization temperature and below the melting point. It has become clear that can be dramatically improved. In addition, it was found that the electrical conductivity improves as the reheating temperature increases in a temperature range where crystal precipitation and melting do not occur remarkably. It has also been found that the holding time may be shortened as the reheating temperature increases. From these phenomena, it is considered that the mechanism by which the electrical conductivity is improved by reheating above the melting point and exceeding the crystallization temperature is due to the activity energy of electrons.

In addition to these experimental examples, vanadium oxide (V 2 O 3), barium oxide (BaO), acid

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The molar ratio of iron oxide (Fe 2 O 3) is 40 to 98 mol%, 1 to 40 mol%, and 1 to 20 mol%, respectively.

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Various oxide glasses were prepared so as to be in the range, the crystallization temperature and melting point of each were determined, and the electrical conductivity at room temperature before and after the reheating process was measured. Reheating as in these experimental examples was performed. It was confirmed that the electrical conductivity increased through the process.

A mixture of vanadium oxide (V O), barium oxide (BaO) and iron oxide (Fe O)

2 5 2 3

Vanadium oxide (V o), dipentaoxide, which can be obtained only by using an oxide glass produced by melting and cooling.

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An acidic glass produced by melting and cooling a mixture of phosphorus (P 2 O 3) and barium oxide (BaO),

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Melting and cooling a mixture of vanadium oxide (V O), potassium oxide (K O), and iron oxide (Fe O)

2 5 2 2 3

It was also confirmed that the electrical conductivity of the oxide glass produced in this way increased through the reheating process.

From the above, it can be said that the production method of the present invention can be widely applied to vanadate glass containing vanadium as a main component or a subcomponent and has high versatility.

[0030] (Reheating time vs. electrical conductivity)

(Example 1)

Re-heated the oxide glass of Experimental Example 2 cooled to below the glass transition temperature in the atmosphere at 500 ° C, which is a temperature exceeding the crystallization temperature (392 ° C) and below the melting point (540 ° C), A certain time from the furnace Each time it was taken out, the electrical conductivity at 25 ° C was measured.

(Example 2)

Re-heated the oxide glass of Example 2 cooled to below the glass transition temperature in the atmosphere at 400 ° C, which is a temperature exceeding the crystallization temperature (392 ° C) and below the melting point (540 ° C), The electrical conductivity at 25 ° C was measured after taking out from the furnace at regular intervals.

(Comparative Example 1)

The oxide glass of Experiment 2 cooled to below the glass transition temperature was reheated in the atmosphere at 350 ° C, which is the glass transition temperature (328 ° C) or higher and the crystallization temperature (392 ° C) or lower. Then, the electrical conductivity at 25 ° C was measured by taking out from the furnace at regular intervals. This reheating condition is the annealing condition described in Japanese Patent Laid-Open No. 2003-34548 (Patent Document 1) (a condition in which the temperature is maintained in the temperature range between the glass transition temperature and the crystallization temperature).

FIG. 3 is a graph showing the relationship between the reheating temperature and reheating time of the oxide glass of Experimental Example 2 and electrical conductivity. In Fig. 3, the horizontal axis represents the holding time at the reheating temperature, and the vertical axis represents the electrical conductivity σ (S′cnT ¹ ) at 25 ° C.

In Examples 1 and 2, the acid-containing glass of Experimental Example 2 cooled to below the glass transition temperature was reheated in the atmosphere at a temperature exceeding the crystallization temperature (392 ° C) and below the melting point (540 ° C). It was confirmed that the electrical conductivity could be improved by more than three orders of magnitude by reheating for only 30 minutes, and that the electrical conductivity hardly fluctuated even if reheating was continued. In addition, it was confirmed that Example 1 having a higher reheating temperature than Example 2 can increase the electrical conductivity.

On the other hand, in Comparative Example 1, which was reheated at a temperature not lower than the glass transition temperature (328 ° C) and not higher than the crystallization temperature (392 ° C), the electrical conductivity increased as the holding time at the reheating temperature increased. It was confirmed that the electrical conductivity could not be kept constant unless maintained for 180 minutes or longer. Further, it was confirmed that the electrical conductivity of Comparative Example 1 was lower by one digit or more than that of Examples 1 and 2.

From the above, according to this example, the electrical conductivity can be drastically increased even if it is held for a short time of about 30 minutes in a predetermined temperature range where the electrical conductivity does not vary depending on the time of holding at the reheating temperature. It was also found that even if the holding time varies, the electric conductivity does not vary and the production stability is remarkably excellent. In addition, reheating process It was revealed that the electrical conductivity of the vanadate glass at room temperature can be designed and controlled with high accuracy in the region of 10 ^_4 S 'cm ^_1 or more by changing the heating time in the glass.

Industrial applicability

The present invention relates to a method for producing a vanadate glass suitably used as an electrode material or the like, and can produce a vanadate glass having a high electrical conductivity of 10 ^_1 S · cm- ¹ or more and a predetermined temperature range. Even if it is held for a short time of about 30 minutes, the electrical conductivity can be dramatically increased, and even if the holding time in a predetermined temperature range varies, there is little fluctuation in the electrical conductivity and production stability and Surface-conduction electron-emitting devices (SCEs) used in SEDs (Surface-conduction Electron-emitter Displays), which use a thermistor only with a heating element and antistatic material, can significantly increase the product yield. Surface-conduction electron-emitter) can provide an optimal method for producing vanadate glass for commercialization of various electrode materials such as fine electron emission electrodes and discharge electrodes.

Claims

The scope of the claims

[1] A method for producing a vanadate glass containing vanadium as a main component or an auxiliary component, comprising a vitrification step of vitrifying a composition containing vanadium to produce an oxide glass, and the oxide glass comprising: And a reheating step of keeping the oxide glass in a temperature range exceeding the crystallization temperature and not higher than the melting point for a predetermined time, and producing a vanadate glass.

[2] The composition contains vanadium, barium and iron! 2. The method for producing a vanadate glass according to claim 1, wherein:

[3] The composition is a mixture containing vanadium oxide, barium oxide and iron oxide, and is obtained by heating and melting the mixture and then rapidly cooling the mixture. The manufacturing method of the vanadate glass of Claim 1 or 2.