JP6473495B1 - Crystalline oxide ceramic short-time firing method and apparatus - Google Patents

Abstract

The present invention provides a method for firing crystalline oxide ceramics in a short time and an apparatus for carrying out the method. A mixed powder S1 obtained by mixing oxide and / or carbonate and / or phosphate powders of elements other than oxygen contained in crystalline oxide ceramics is obtained by molding S2. Preliminary firing step S3 for prefiring the molded body, and average grain size of crystal grains at a main firing temperature of 1000 to 1100 ° C. in a pressurized gas atmosphere with compressed air using an absolute pressure of 0.33 to 0.38 MPa. The main body includes a main baking step S4 that is fired until the diameter reaches 2 to 5 μm, and the time required for the main baking step S4 is less than a quarter of that in the case where the main baking step S4 is performed in an air atmosphere. Oxide ceramics short-time firing method and manufacturing equipment for carrying out the method. [Selection] Figure 14

Description

  The present invention relates to a production method for firing crystalline oxide ceramics in a short time and an apparatus for carrying out the production method.

  In order to produce crystalline oxide ceramics by the solid phase method, first, the raw material powder is mixed well, molded by pressing, etc., and then calcined at a low temperature to remove moisture and unnecessary elemental components. After firing in the form of water vapor, carbon dioxide, etc., the main firing is performed. Thereafter, if necessary depending on the application, a post-treatment process such as a reduction treatment or an annealing treatment at a high temperature may be performed.

  Japanese Patent Laid-Open No. 11-116330 (Patent Document 1) discloses a low-pressure sintering at a relatively low temperature of 1150 ° C. or lower in the first stage as a main firing method for producing a translucent high-density PLZT ceramic. Is followed by a continuous two-stage sintering method in which a second stage of pressurized oxygen sintering at a high temperature of 1200 ° C. or higher is performed. Since the firing method of Patent Document 1 has a problem of ensuring the translucency and denseness of ceramics, the densification is advanced and the translucency is ensured in the pressurized oxygen sintering at a high temperature in the second stage. To the extent possible, it is necessary to reduce the scattering of light by grain boundaries and pores. However, for example, for phosphors, it is necessary to determine whether or not it is possible to manufacture by a main firing in a pressurized gas atmosphere of less than 1200 ° C. in a method for firing a general crystalline oxide ceramic that does not necessarily require translucency and denseness. The conditions are not clear at all.

JP 2009-185202 A (Patent Document 2) discloses a composition formula Li _{1 + xy} Nb _1-x-3y Ti _{x + 4y} O ₃ (x) in which titanium is dissolved in lithium niobate activated by europium. And y satisfy 0.04 ≦ x ≦ 0.33 and 0 ≦ y ≦ 0.09, and the addition amount of Eu ₂ O ₃ is 0.5 to 3.0 wt%. It is described that a crystalline oxide ceramic phosphor can be manufactured by a solid phase method. However, the production method involves dry mixing the raw materials and baking in an air atmosphere at 1000 ° C. for 3 hours and 1120 ° C. for 10 to 15 hours, and the production takes a very long time.

H. Nakano et al, Materials Research Bulletin 83 (2016) 502-506 (Non-patent Document 1) is a kind of crystalline oxide ceramics and has a composition formula (Ca _{2-x / 2-y} Eu _y □ _{x / 2} ) (Si _1-x P _x ) O ₄ (where 0 ≦ x ≦ 0.20 and 0.02 ≦ y ≦ 0.05) In the case where the main baking is performed at a temperature of ˜1500 ° C., it is described that homogeneous baking can be performed after repeating pulverization and mixing and baking many times over a long time of 24 hours or more.

Shohei Furuya, Asuka Okumi, Hiromi Nakano, Journal of Powder Engineering, Vol. 53, No. 5, 2016, 4-8 pages (Non-patent Document 2) is a kind of crystalline oxide ceramics and has a composition formula ( Ba _1-x Eu _x ) _0.79 (Al _1-y Zn _y ) _10.9 O _17.14- δ (where 0.01 ≦ x ≦ 0.2 and 0 ≦ y ≦ 0.1) It is described that can be baked and produced in an air atmosphere by a solid phase method. However, for homogeneous firing in which the average grain size of the crystal grains reaches 2 to 5 μm, after repeatedly firing and mixing and firing at a temperature of 1200 ° C. many times for the fired body after temporary firing, Furthermore, as a post-treatment step, it is necessary to calcinate at 1550 ° C. for 4 hours, and synthesis (firing production) requires a very long time and labor.

JP-A-11-116330 JP 2009-185202 A

H. Nakano et al, Materials Research Bulletin 83 (2016) 502-506. Shohei Furuya, Asuka Okumi, Hiromi Nakano, Journal of Powder Engineering, Vol. 53, No. 5, 2016, 4-8 pages

  Therefore, the object of the present invention is to use a pressurized gas atmosphere furnace in the firing of crystalline oxide ceramics, and to control an optimum pressurized gas atmosphere so far, an electric furnace in an air atmosphere has been used. To find a firing condition for realizing homogeneous grain growth at a low temperature and in a short time for a material that has required a long time for firing, and to provide a short-time firing method for crystalline oxide ceramics using the firing condition, And it is providing the apparatus for it.

The present invention has been made to solve the above problems, and a first aspect of the present invention is a method for producing a crystalline oxide ceramic by firing,
Using compressed air, the average pressure of the crystal grains reaches the target crystal grain size according to the application at a main firing temperature of less than 1200 ° C under a pressurized gas atmosphere in which the absolute pressure is included in the preferred absolute pressure section. A crystalline oxide ceramic comprising a main baking step for baking until the main baking step is performed in an air atmosphere, and the time required for the main baking step is one quarter or less. This is a short-time firing method.

  In the second embodiment of the present invention, prior to the main firing step, oxides and / or carbonates and / or phosphates of elements other than oxygen contained in the crystalline oxide ceramics are mixed. This is a crystalline oxide ceramic short-time firing method including a pre-firing step of forming a mixed powder and pre-firing the obtained compact.

According to a third aspect of the present invention, the preferred absolute pressure section is 0.33 to 0.38 MPa, the main firing temperature is 1000 to 1100 ° C., and the target crystal grain size is 2 to 5 μm. This is a ceramic short-time firing method.

According to a fourth aspect of the present invention, the crystalline oxide ceramic has a composition formula Li _{1 + xy} Nb _1-x-3y Ti _{x + 4y} O ₃ (where 0.07 ≦ x ≦ 0.33 and 0 ≦ y ≦ 0.175), which is an LNT ceramic that forms a superstructure having a constant periodic interval, and the mixed powder is a mixed powder obtained by mixing LiCO ₃ , Nb ₂ O ₅ , and TiO ₂ powders, The superstructure is a crystalline oxide ceramic short-time firing method that is a periodic structure formed by diffusion of Ti atoms.

According to a fifth aspect of the present invention, when the composition of LNT ceramics is changed within a Ti concentration range of 15 to 30 mol%, the higher the Ti concentration, the smaller the periodic interval of the superstructure becomes. This is a ceramic short-time firing method.

In a sixth aspect of the present invention, the mixed powder contains a total of 0.5 to 5 % by mass of RE ₂ O ₃ powder, and the LNT ceramic is a crystalline oxide ceramic in which RE is activated, and the RE Is a crystalline oxide ceramic short-time firing method that is one or more of the rare earth elements Dy, Er, Eu, Nd, Pr, Sm, Tm, Tb, and Yb.

According to a seventh aspect of the present invention, the crystalline oxide ceramics has a composition formula (Ca _{2−x / 2−y} Eu _y □ _{x / 2} ) (Si _1−x P _x ) O ₄ (where 0 ≦ x ≦ 0.20 and 0.02 ≦ y ≦ 0.5), and the mixed powder is made of CaCO ₃ , SiO ₂ , CaHPO ₄ .2H ₂ O, Eu ₂ O ₃ . It is a mixed powder in which powder is mixed, and includes a post-processing step performed after the main baking step. In the post-processing step, annealing is performed in an air atmosphere, and Eu ³⁺ ions are further reduced in a reducing gas. This is a crystalline oxide ceramic short-time firing method in which reduction treatment to reduce Eu ²⁺ ions is performed.

In an eighth aspect of the present invention, the crystalline oxide ceramics has a composition formula (Ba _1-x Eu _x ) _0.79 (Al _1-y Zn _y ) _10.9 O _17.14- δ (where 0.01 ≦ x ≦ 0 .2 and 0 ≦ y ≦ 0.1), and the mixed powder is a mixed powder obtained by mixing powders of BaCO ₃ , Al ₂ O ₃ , ZnO, and Eu ₂ O _3. Yes, including a post-treatment step performed after the main firing step, in which the annealing treatment is performed in an air atmosphere, and Eu ³⁺ ions are reduced to Eu ²⁺ ions in a reducing gas. It is a crystalline oxide ceramic short-time firing method for performing reduction treatment.

A ninth aspect of the present invention is an apparatus for carrying out the above-mentioned crystalline oxide ceramic short-time firing method, a firing furnace that can be kept airtight, and a raw material that is disposed in the firing furnace. A holding unit for holding the mixed powder or a molded body thereof, a heating unit, a pressurized gas introduction unit that pressurizes and feeds a mixed gas containing oxygen into the firing furnace, and releases the gas in the firing furnace to the outside. A crystalline oxide ceramic short-time firing apparatus having at least a gas discharge means.

A tenth aspect of the present invention is a crystalline material comprising a control unit that includes a timer and performs program control for automatically adjusting the temperature of the mixed powder or the molded body thereof and the pressure of the gas in the firing furnace. This is an oxide ceramic short-time firing device.

According to the first aspect of the present invention, there is provided a method for producing a crystalline oxide ceramic by firing, using compressed air, and an absolute pressure of less than 1200 ° C. under a pressurized gas atmosphere included in a preferred absolute pressure section. In comparison with the case where the main baking step is performed in an air atmosphere, the main baking step is performed until the average particle size of the crystal grains reaches the target crystal particle size according to the application. It is possible to provide a crystalline oxide ceramic short-time firing method characterized in that the time required for the main firing step is ¼ or less.
When using compressed air and firing at a main firing temperature of less than 1200 ° C. in a pressurized gas atmosphere where the absolute pressure is 0.6 MPa or less and the absolute pressure is not so high, the absolute pressure is optimal for homogeneous grain growth. Conventionally, it has not been known that grain growth may be hindered when the absolute pressure is higher than that. The present invention significantly shortens the time required for the main baking process compared to the prior art by performing baking in a pressurized gas atmosphere of an absolute pressure included in a preferred absolute pressure section close to the optimum absolute pressure. It is.
Here, the preferred absolute pressure section is 0.6 MPa or less, in which the time required for the main baking step is one quarter or less, compared to the case where the main baking step is performed under the same temperature conditions in an air atmosphere. It is an arbitrary section of absolute pressure. The inventor's discovery is that the diffusion mechanism depends on the crystal structure (space group), but there may be many crystalline oxide ceramics capable of setting a preferred absolute pressure interval. It is in. The preferred absolute pressure section does not necessarily include the optimum absolute pressure described above, but it is desirable to include it.

According to the second aspect of the present invention, there is provided a crystalline oxide ceramic short-time firing method including a pre-firing step of forming a mixed powder obtained by mixing raw material powders and pre-firing the obtained compact. can do.
The pre-baking process is carried out to make it easy to handle fragile compacts as they are, and prior to the main firing process, the unnecessary elements contained in the compacts are blown out in the form of gases such as moisture and carbon dioxide. Is done. The calcination temperature can be selected, for example, from 500 to 850 ° C.

  According to the third aspect of the present invention, the preferred absolute pressure section is 0.33 to 0.38 MPa, the main firing temperature is 1000 to 1100 ° C., and the target crystal grain size according to the application is 2 to 5 μm. A crystalline oxide ceramic short-time firing method can be provided.

  The present inventor performs main firing at a low temperature of 1000 to 1100 ° C. in a pressurized gas atmosphere using compressed air to produce LNT ceramics which are typical crystalline oxide ceramics. The growth rate of the average particle diameter is maximized when the absolute pressure is about 0.35 MPa or within the range of 0.33 to 0.38 MPa. We found that homogeneous grain growth was hindered. Furthermore, when firing in a pressurized gas atmosphere having an absolute pressure of 0.33 to 0.38 MPa, the average grain size of the crystal grains becomes the target crystal grain size compared to firing in an air atmosphere. It was confirmed with LNT ceramics and some ceramic phosphors, which are crystalline oxide ceramics, that the time required for the main firing step of firing until reaching the required time is one quarter or less.

  When producing crystalline oxide ceramics by firing in a pressurized gas atmosphere at a low temperature of 1000 to 1100 ° C., the optimum absolute pressure (about 0.35 MPa) that maximizes the growth rate of the average grain size of the crystal grains It has not been conventionally known that homogeneous grain growth may be hindered by an absolute pressure higher than 0.33 to 0.38 MPa). The mechanism is 0.33-0.38MPa in oxide, the most efficient, and oxygen between quasi-lattices cooperates with vacancies, while oxygen atoms push out oxygen like a ball and promote diffusion of atoms. I think. On the other hand, if the absolute pressure becomes too high, the concentration of gas (oxygen) molecules increases, so that the oxygen ions repel each other and the diffusion of atoms is conversely inhibited. Note that the present inventor uses a mixed gas of oxygen and nitrogen to maintain the average pressure of the crystal grains even if the molar ratio of oxygen in the mixed gas is changed while keeping the absolute pressure constant at 1 atm (0.1 MPa). Experimental results have shown that the growth rate of diameter may not change much, and the mechanism may involve not only the oxygen partial pressure but also the absolute pressure.

  In this embodiment, compressed air is used as the pressurized gas. However, for example, it is considered that the same effect can be obtained if the pressurized gas is a mixed gas of oxygen and an arbitrary gas.

  The main firing step of the present embodiment is completed when the average crystal grain size reaches the target crystal grain size of 2 to 5 μm. The crystal grains of the crystalline oxide ceramics need to have an optimum particle size that satisfies a certain condition with respect to the grain size of the crystal grains, depending on the application. In the main firing step of this embodiment, it is confirmed that the crystal grains of the obtained crystalline oxide ceramics have an average particle size of 2 to 3 μm or more, which is a particle size suitable for at least phosphor use.

According to a fourth aspect of the present invention, the crystalline oxide ceramic is an LNT ceramic that is expressed by the composition formula and forms a superstructure having a constant periodic interval, and the superstructure is composed of Ti atoms. A crystalline oxide ceramic short-time firing method having a periodic structure formed by diffusion can be provided.
The LNT ceramics represented by the composition formula has a periodic structure formed by diffusion of Ti atoms, called a superstructure. Whether or not the superstructure is formed by firing, and whether or not the periodic interval of the formed superstructure is constant, is it possible to achieve uniform crystal grain growth along with the average grain diameter of the crystal grains? This is a good index for determining
Conventionally, in order to form a superstructure having a constant periodic interval, for example, in an air atmosphere, at a temperature of 1120 ° C., for a long time of a total of 24 to 240 hours, that is, grinding / mixing and firing It was necessary to repeat. In this embodiment of the present invention, the absolute pressure is 0.33 to 0.33.
By firing at a low temperature of 1000 to 1100 ° C. in a pressurized gas atmosphere of 0.38 MPa, the firing process is completed in a time that is less than a quarter of the conventional structure, and a superstructure having a constant periodic interval. Can be formed.

  When the composition of the LNT ceramic is changed within a Ti concentration range of 15 to 30 mol%, the time required for the main firing step is shortened as the Ti concentration is increased. Therefore, the time required for the main firing step can be controlled by changing the Ti concentration.

According to the fifth aspect of the present invention, when the composition of the LNT ceramic is changed in the range of Ti concentration of 15 to 30 mol%, the crystalline structure in which the constant period interval of the superstructure becomes narrower as the Ti concentration is higher. An oxide ceramic short-time firing method can be provided.
The superstructure is a periodic structure in which an intergrowth layer is formed of Ti atoms. More precisely, an intergrowth layer containing a large amount of Ti atoms and a matrix layer containing a minimum amount of Ti atoms are periodically stacked. It is. Therefore, as the Ti concentration increases, the interval between the inter-growth layers becomes narrower. In other words, when a large number of Ti atoms enter, they are difficult to dissolve in the matrix phase, so that excess Ti atoms form a larger number of intergrowth layers, and the constant periodic interval of the superstructure is narrowed.

  Since the intergrowth layer has a structure different from that of the parent phase, the formation mechanism is different from that of other general periodic structures of oxide ceramics, for example, the periodicity of the stack, the periodicity of the layered structure, the Ruddlesden-Popper phase, etc. Different. Therefore, the presence or absence of the formation of a superstructure having a constant periodic interval is a good index for determining whether or not uniform crystal growth is realized. The present inventor has realized the uniform crystal growth in the main firing of the crystalline oxide ceramics in a pressurized gas atmosphere at a low temperature by investigating whether or not a superstructure having a certain periodic interval is formed. The absolute pressure range that maximizes the growth rate of the average grain size of the grains has been found.

According to the sixth aspect of the present invention, the mixed powder contains a total of 0.5 to 5 % by mass of RE ₂ O ₃ powder, and the LNT ceramic is a crystalline oxide ceramic activated RE. The RE can provide a crystalline oxide ceramic short-time firing method that is one or more of the rare earth elements Dy, Er, Eu, Nd, Pr, Sm, Tm, Tb, and Yb. The crystalline oxide ceramics in which RE is activated in this embodiment can be used for phosphors.

According to a seventh aspect of the present invention, the crystalline oxide ceramic is a silicate ceramic phosphor represented by the composition formula, and the mixed powder is CaCO ₃ , SiO ₂ , CaHPO ₄ .2H _2. A mixed powder in which powders of O and Eu ₂ O ₃ are mixed, and a crystalline oxide ceramics short-time firing method including a post-treatment step performed after the main firing step can be provided.
In the case of producing the silicate ceramic phosphor, after the preliminary firing, a main firing step of firing in an air atmosphere is performed using an electric furnace or the like, and then a post-processing step is performed. In the case of firing at a low temperature of 1000 to 1100 ° C. in the conventional main firing process, a planetary ball mill is used for pulverization and mixing many times for homogeneous firing in which the average grain size of the crystal grains reaches 2 to 5 μm. It was necessary to repeat firing, and the production required a time and labor of the main firing process of 24 hours or more. In the present embodiment of the present invention, by performing the main baking step in a pressurized gas atmosphere having an absolute pressure of 0.33 to 0.38 MPa, the time of the main baking step is less than a quarter of that in the conventional case. The main calcination step is completed by one-time calcination, and then a post-treatment step is performed to manufacture the silicate ceramic phosphor.

According to an eighth aspect of the present invention, the crystalline oxide ceramic is a barium-based ceramic phosphor represented by the composition formula, and the mixed powder is BaCO ₃ , Al ₂ O ₃ , ZnO, Eu. It is a mixed powder obtained by mixing ₂ O ₃ powder, and can provide a crystalline oxide ceramic short-time firing method including a post-treatment step performed after the main firing step.

  In the case of producing the barium-based ceramic phosphor, after the preliminary firing, a main firing step of firing in an air atmosphere is performed using an electric furnace or the like, and then a post-processing step is performed. In the conventional main firing step, when firing at a low temperature of 1000 to 1100 ° C., no matter how much firing time is taken and the pulverization / mixing and firing are repeated many times, the homogeneous firing cannot be succeeded. Even in the case where the main baking process is performed in an air atmosphere at a high temperature of 1200 ° C., in order to perform uniform baking in which the average grain size of the crystal grains reaches 2 to 5 μm, a planetary ball mill is used. In addition, it was necessary to repeat the pulverization and mixing and firing, and the production required a time and labor of the main firing process of 50 hours or more. In the present embodiment of the present invention, by performing the main baking step in a pressurized gas atmosphere having a low temperature of 1000 to 1100 ° C. and an absolute pressure of 0.33 to 0.38 MPa, the time of the main baking step is only 2 hours. The main firing step can be completed by one firing, and then a post-treatment step can be performed to produce the barium-based ceramic phosphor.

According to a ninth aspect of the present invention, there is provided an apparatus for carrying out the above-mentioned crystalline oxide ceramic short-time firing method, a firing furnace that can be kept airtight, and disposed in the firing furnace, A holding unit for holding the mixed powder or a molded body thereof, a heating unit, a pressurized gas introduction unit that pressurizes and feeds a mixed gas containing oxygen into the firing furnace, and releases the gas in the firing furnace to the outside. A crystalline oxide ceramic short-time firing apparatus having at least a gas discharge means can be provided.
Since the apparatus of this embodiment of the present invention has a firing furnace, pressurized gas introduction means and gas discharge means that can be kept airtight, it is possible to keep the absolute pressure in the firing furnace within the range of the preferred absolute pressure section. Moreover, since it has a heating means, the mixed powder or a molded product thereof can be fired in a pressurized gas atmosphere at a temperature of at least 1200 ° C. or less. Therefore, the crystalline oxide ceramic short-time firing method can be carried out using the apparatus.

  According to a tenth aspect of the present invention, a timer is provided, and a control unit is provided that performs program control for automatically adjusting the temperature of the mixed powder or its molded body and the pressure of the gas in the firing furnace. A crystalline oxide ceramic short-time firing apparatus can be provided.

FIG. 1 is a flowchart showing a general firing method for crystalline oxide ceramics. FIG. 2 is a scanning electron microscope (SEM) photograph showing the degree of growth of crystal grains by changing the absolute pressure of the pressurized gas in the main firing step of LNT ceramics in four ways. FIG. 3 is a graph showing the relationship between the absolute pressure of the pressurized gas and the average grain size of the crystal grains in the main firing step of LNT ceramics. FIG. 4A is a diffractogram of a transmission electron microscope (TEM) of LNT ceramics produced by the crystalline oxide ceramic short-time firing method according to the present invention, and FIG. It is a TEM photograph figure shown. FIG. 5 shows X-rays of LNT ceramics produced by firing at a main firing temperature of 1000 ° C. for 1 hour in the crystalline oxide ceramic short-time firing method according to the present invention, with the composition being changed in four ways with different Ti concentrations. It is a diffraction (XRD) pattern figure (4 composition). FIG. 6 is a SEM photograph (4 compositions) of LNT ceramics fired and produced at a main firing temperature of 1000 ° C. for 1 hour. FIG. 7 is also a TEM image of a LNT ceramic (Ti concentration: 15 mol%) produced by firing at a main firing temperature of 1000 ° C. for 1 hour and a TEM photograph showing inhomogeneous formation of the superstructure. FIG. 8 is also a TEM image of a LNT ceramic (Ti concentration 30 mol%) baked and manufactured at a main calcination temperature of 1000 ° C. for 1 hour and a TEM photograph showing homogeneous formation of the superstructure. FIG. 9 is an XRD pattern of LNT ceramics produced by firing at a main firing temperature of 1100 ° C. for one hour by changing the composition in four ways with different Ti concentrations and using the crystalline oxide ceramic short-time firing method according to the present invention. It is a figure (4 compositions). FIG. 10 is an SEM photograph (4 compositions) of LNT ceramics fired and manufactured at a main firing temperature of 1100 ° C. for 1 hour. FIG. 11 is a graph showing the lattice constant of LNT ceramics (4 compositions) synthesized (fired and manufactured) at 1000 ° C. and 1100 ° C. main firing temperatures for 1 hour, with the Ti concentration on the horizontal axis. FIG. 12 shows a sample obtained by subjecting the silicate-based ceramic phosphor to a main firing step for 24 hours in an air atmosphere and a main firing step for 6 hours using the crystalline oxide ceramic short-time firing method according to the present invention. It is a comparison figure of an XRD pattern of a sample. FIG. 13 shows a sample obtained by subjecting the barium-based ceramic phosphor to a firing process in an air atmosphere for 50 hours, and a firing process for 2 hours in the crystalline oxide ceramic short-time firing method according to the present invention. It is a comparison figure of an XRD pattern of a sample. FIG. 14 is a flowchart of the crystalline oxide ceramic short-time firing method and optional post-treatment process according to the present invention. FIG. 15 is a schematic cross-sectional view of a crystalline oxide ceramics short-time firing apparatus according to the present invention, including an explanatory diagram of a control unit of the apparatus.

  Next, the form for implementing the crystalline oxide ceramics short time baking manufacturing method and apparatus of this invention is demonstrated in detail, referring drawings and a table | surface.

  The feature of the present invention is that, with respect to the method for firing crystalline oxide ceramics, a pressurized gas atmosphere furnace is used, and the optimum pressurized gas atmosphere is controlled, so that an electric furnace in an atmospheric atmosphere has long been synthesized. It is the point which discovered the optimal conditions which carry out homogeneous baking and the growth of a crystal grain in low temperature and a short time about the required material.

  FIG. 1 shows a general method for producing crystalline oxide ceramics by a solid phase method. The average particle size of the oxide or the like powder used as a raw material is desirably equal to or less than the reference powder particle size. The standard powder particle size is, for example, 0.1 to 0.3 μm. First, after mixing the powder used as a raw material and shape | molding the obtained mixed powder, the temporary baking process which pre-bakes a molded object is implemented, and the main baking process which performs main baking is then implemented. When post-treatment such as reduction treatment or annealing treatment is performed on the obtained fired body, a post-treatment process is performed to complete the firing production. In the case where no post-treatment is performed, the baking production is completed by the end of the main baking step.

The crystalline oxide ceramic short-time firing method of the present invention relates to the main firing step among the above steps. In the case where the main baking is performed in two stages, ie, a first stage baking performed at a relatively low temperature and a second stage baking performed at a relatively high temperature, the first stage baking is performed according to the present invention. In some cases, the “firing process” and the second stage firing correspond to the “annealing process” of the present application.
Conventionally, the firing process, which has been performed in an air atmosphere for a long time, is performed at a temperature of less than 1200 ° C., for example, 1000 to 1000 ° C. in a pressurized gas atmosphere at an optimum absolute pressure using a pressurized gas atmosphere furnace. By carrying out at a low temperature of 1100 ° C., homogeneous firing and crystal grain growth could be realized in a short time of the main firing step. In addition, in the conventional firing process in the conventional atmospheric atmosphere, the firing process according to the firing method of the present invention is also applicable to materials that normally have to be repeatedly pulverized, mixed, and fired to promote the sintering reaction. Then, the repetition of pulverization / mixing and firing is unnecessary, and the firing is performed only once, and no sintering aid is required.
Table 1 below shows a difference between the conventional firing process and the firing process of one embodiment of the present invention.

  Table 2 above shows the relationship between absolute pressure, gauge pressure, and oxygen partial pressure for the pressurized gas in the firing furnace. The gauge pressure is smaller than the absolute pressure by atmospheric pressure (0.101 MPa). When compressed air is used for firing, oxygen is contained in the air in a molar ratio of 20.6%, so the oxygen partial pressure in the firing furnace is 0.206 times the absolute pressure. The present invention mainly assumes the use of compressed air as a pressurized gas, but uses a mixed gas of oxygen and any gas, for example, a mixed gas in which nitrogen in compressed air is replaced with a rare gas. However, it is considered that the same actions and effects as those of the present invention are exhibited.

<Example 1: LNT ceramics>
LNT ceramics, which are typical crystalline oxide ceramics, have a composition formula Li _{1 + xy} Nb _1-x-3y Ti _{x + 4y} O ₃ (where 0.07 ≦ x ≦ 0.33 and 0 ≦ y ≦ 0. 175) and can form a superstructure. This superstructure is a periodic structure formed by diffusion of Ti element. Conventionally, when firing in an electric furnace in an air atmosphere, a long firing time of 24 to 240 hours at a main firing temperature of 1120 ° C. was required to form this superstructure (H. Nakano et al. Journal of Alloys and Compounds 618 (2015) pp. 504-507).
This time, by using a pressurized gas atmosphere furnace, when compressed air is used and the absolute pressure is 0.35 MPa (oxygen partial pressure 0.7 atm), the main firing temperature of 1100 ° C. is as short as 30 minutes to 1 hour. Since it became clear that crystal grains grew over time and formed a uniform periodic structure, the following data is shown.

<Example 1-1> Examination of the most suitable absolute pressure In the case of firing and manufacturing LNT ceramics (x = 0.160, y = 0.020) having a Ti concentration of 20 mol%, the pressure of compressed air is We changed the pressure to examine the most grain growth. The scanning electron microscope which imaged the degree of grain growth in a calcination object (sample numbers # 1- # 4) at the time of changing absolute pressure from 0.30MPa to 0.45MPa in a figure (2A)-figure (2D). (SEM) A photograph is shown. Crystal grains 11 and pores 12 can be confirmed. From FIG. 2, it can be seen that the grain growth is the most when the absolute pressure is 0.35 MPa (sample number # 2) and the grain growth is homogeneous. When the absolute pressure is 0.30 MPa or 0.45 MPa, the degree of grain growth does not progress as much as when the degree of grain growth is 0.35 MPa, and the uniformity of grain growth is not good. The conditions for the main firing are shown in Table 3 below.

  Table 3 shows the above samples (# 1 to # 4) and additional samples (# 5 and # 6) obtained by performing the main firing in a pressurized gas atmosphere having absolute pressures of 0.50 MPa and 0.60 MPa. About the conditions of this baking and the average particle diameter of the obtained crystal grain are shown. The average particle size is calculated according to the normal particle size measurement method, using the commercially available measurement software for the crystal grains in the SEM photograph, measuring the maximum diameter for 200 or more crystal grains, and calculating the average value. It is a thing.

  FIG. 3 is a graph of Table 3, and is a graph showing the relationship between the absolute pressure in the main firing step and the average grain size of the crystal grains. The average grain size of the crystal grains becomes maximum when the absolute pressure is 0.35 MPa. Although the firing temperature is as low as 1100 ° C. and the firing time is as short as 30 minutes, the average grain size grows to 2.6 μm in a pressurized gas atmosphere with an absolute pressure of 0.35 MPa. To do. Also, in a pressurized gas atmosphere having an absolute pressure of 0.33 to 0.38 MPa, the average grain size of the crystal grains grows to 2.4 μm or more, and in a pressurized gas atmosphere having an absolute pressure of 0.30 to 0.42 MPa. It can be seen that the average grain size grows to 2.0 μm or more.

FIG. 4 shows a transmission electron microscope (TEM) photograph taken from the [010] orientation for the case where the absolute pressure is 0.35 MPa (sample number # 2) where the most grains have grown. FIG. 4A is a TEM diffraction pattern showing the presence of a regular crystal lattice. FIG. 4B is a TEM photograph showing the formation of the superstructure, and it can be seen that a uniform periodic structure was formed at intervals of 4.5 nm.
That is, a superstructure having a constant periodic interval 21 of 4.5 nm is formed.

<Example 1-2> Examination of influence of Ti concentration and main baking temperature on superstructure formation Absolute pressure was fixed to 0.35 MPa, main baking time was fixed to one hour, and main baking temperature was 1000 ° C. and 1100. In the case of ° C., the composition of LNT ceramics (x = 0.125-0.176, y = 0-0.063) was changed in the range of Ti concentration of 15-30 mol%, and the formation of a homogeneous superstructure was examined. did.
The results are shown in Table 4 and FIGS.

At a main firing temperature of 1000 ° C., a superstructure was formed when the Ti concentration was as small as 15 mol%, but the periodic interval of the superstructure was different depending on the location and the homogeneity was poor (sample number # 7). On the other hand, when the Ti concentration is higher than 15 mol%, a superstructure having a constant periodic interval was formed, and a uniform superstructure formation could be confirmed. That is, the condition of the main firing of “1000 ° C., 15 mol%, 1 hour” corresponds to a boundary case. Compared to this case, the main firing temperature is higher, the Ti concentration is higher, or the main firing step. If the time is long, it is considered that a homogeneous superstructure is formed.
Further, at a main firing temperature of 1100 ° C., formation of a homogeneous superstructure was confirmed with all compositions.

  FIG. 5 is a diagram showing X-ray diffraction (XRD) patterns 32 of four different composition LNT ceramics (sample numbers # 7 to # 10) that were fired and manufactured at a main firing temperature of 1000 ° C. for 1 hour. In all four compositions, the diffraction peak at an angular position of about 24 degrees is split into two satellite peaks (33 and 34). The higher the Ti concentration, the farther the angular positions of both peaks are. Reflecting the formation of the structure, the higher the Ti concentration, the narrower the (constant) periodic interval 21 of the superstructure.

  FIG. 6 is an SEM photograph of four different composition LNT ceramics (sample numbers # 7 to # 10) that were fired and manufactured at a main firing temperature of 1000 ° C. for 1 hour.

  FIG. 7A is a TEM image of an LNT ceramic (sample number # 7) having a composition of Ti concentration of 15 mol%, which is produced by firing at a main firing temperature of 1000 ° C. for 1 hour. FIG. 7B is also a TEM photograph. Although the superstructure is formed, the periodic interval 21 of the superstructure differs from 5.5 nm or 7.0 nm depending on the location, indicating that the periodicity of the superstructure is inhomogeneous.

The figure (8A) shows a Ti concentration of 30 mo produced by firing at a main firing temperature of 1000 ° C. for 1 hour.
It is a diffraction image figure by LEM of LNT ceramics (sample number # 10) of a composition of 1%. FIG. 8B is also a TEM photograph showing the formation of a homogeneous superstructure. It can be seen that the period interval 21 is constant at 3.0 nm, and the superstructure is formed uniformly.

  FIG. 9 is an X-ray diffraction (XRD) pattern diagram of LNT ceramics (Sample Nos. # 11 to # 14) having four different compositions that were fired and manufactured at a main firing temperature of 1100 ° C. for 1 hour. In all four compositions, satellite peaks (33 and 34) are observed around the (012) reflection, and the higher the Ti concentration, the farther the angular positions of both peaks are. This splitting reflects the formation of the superstructure, indicating that the higher the Ti concentration, the narrower the (constant) periodic interval 21 of the superstructure.

  FIG. 10 is an SEM photograph of four different composition LNT ceramics (sample numbers # 11 to # 14) that were fired and manufactured at a main firing temperature of 1100 ° C. for 1 hour. Homogeneous growth of crystal grains is observed, and the average grain size reaches about 3 μm or more.

FIG. 11 shows LNT ceramics (sample numbers # 7 to # 10) fired (synthesized) for 1 hour at a main firing temperature of 1000 ° C. and LNT ceramics (sample number) fired (synthesized) for 1 hour at a main firing temperature of 1100 ° C. Each of the lattice constants of # 11 to # 14) is compared with the vertical axis representing the Ti concentration and the horizontal axis representing the Ti concentration. FIG. 11A shows the length of the a-axis (a-axis lattice constant), and FIG. 11B shows the length of the c-axis (c-axis lattice constant).
The crystal grains of LNT ceramics are isotropic when no superstructure is formed, but when superstructures are formed, they become crystal grains having plate-like anisotropy. This narrow plate-like direction corresponds to the c-axis, and anisotropy appears when the length of the c-axis suddenly decreases.
Considering the case where the Ti concentration is 15 mol%, the length of the a-axis is reduced by about 0.01% in proportion to the length of the c-axis when the main baking temperature is 1100 ° C. compared to 1000 ° C. Is approximately 0.73% shorter in proportion. That is, the length of the c-axis is abruptly shortened. This is considered to be because, although the superstructure is formed at 1000 ° C., the homogeneity thereof is poor, whereas at 1100 ° C., a homogeneous superstructure is formed and anisotropy appears.
Even in the case where the Ti concentration is higher than 15 mol%, anisotropy in which the length of the c-axis is shortened when the firing temperature is 1100 ° C. as compared with the case where the main baking temperature is 1000 ° C. is observed. Is smaller than 15 mol%. This is considered to be because in the case where the Ti concentration is higher than 15 mol%, the formation of a homogeneous superstructure is almost completed even when the main firing temperature is 1000 ° C.

<Example 2: In the case of ceramic phosphor>
The two ceramic phosphors shown in the following Table 5 are both crystalline oxide ceramics, and conventionally it was difficult to produce them by solid phase reaction. In order to advance the reaction, it was necessary to repeat the pulverization and mixing to bring out a new surface many times and promote the reaction. In order to perform homogeneous firing by the solid-phase method in an air atmosphere, it was necessary to repeat crushing, mixing and firing many times using a planetary ball mill. This time, by using a pressurized gas atmosphere furnace and using a pressurized gas atmosphere having an optimum absolute pressure, a homogeneous phase was successfully formed by a short firing process at a low temperature without using a sintering aid. did.

<Example 2-1> silicate-based ceramic phosphors when the composition formula _{(Ca 2-x / 2-} y Eu y □ x / 2) (Si 1-x P x) O 4 ( provided that 0 ≦ x ≦ 0. In the solid phase method, the silicate ceramic phosphor represented by 20 and 0.02 ≦ y ≦ 0.5) is formed by forming a mixed powder as a raw material, pre-baking the formed body, and performing the main firing step. Then, it is manufactured by performing a post-treatment process. When performing the main firing step in an air atmosphere, for homogeneous firing in which the average grain size of the crystal grains reaches 2 to 5 μm, it is repeatedly performed at 1000 ° C. by pulverization and mixing using a planetary ball mill. It is necessary to repeat pulverization / mixing and firing (Non-patent Document 1). However, according to the crystalline oxide ceramics short-time firing method of the present invention, by firing and producing in a pressurized gas atmosphere with an absolute pressure of 0.35 MPa, the time of the main firing step is 6 hours, Below, pulverization and mixing and firing were repeated in an electric furnace, and crystal grain homogeneity and average grain size equivalent to those obtained by firing for a total time of 24 hours could be obtained.

FIG. 12 shows that the silicate ceramic phosphor with y = 0.3 and x = 0.06 was repeatedly pulverized and mixed and fired while confirming the XRD pattern until a homogeneous phase was obtained. After baking at the main baking temperature for a total baking time of 24 hours, the post-processing step (sample number # 115) and the crystalline oxide ceramics short-time baking manufacturing method according to the present invention Comparison of XRD patterns of those manufactured by performing a post-treatment process after firing at a main firing temperature of 1000 ° C. in a pressurized gas atmosphere with an absolute pressure of 0.35 MPa for 6 hours (sample number # 15) FIG.
The peak angle positions and the relative intensities of the peaks found in the XRD patterns of Sample No. # 115 and Sample No. # 15 are almost the same, and the main firing step was performed by the crystalline oxide ceramic short-time firing method of the present invention. It can be seen that the sample (sample number # 15) and the sample subjected to the main baking step for a long time in the air atmosphere (sample number # 115) are substantially equivalent in the regularity of the crystal structure of the crystal grains.

In addition, before the main baking step at the above main baking temperature, a preliminary baking step was performed in which the contained gas components and the like were sufficiently skipped at 700 to 800 ° C. for several hours in the air atmosphere. Further, in the main firing step, a reaction is formed in which a parent phase crystal structure formed by the reaction of CaO and SiO _{2 has} a crystal structure in which P ions and Eu ions as activators (emission center ions) are replaced by solid solution. Is happening. Furthermore, the post-processing process was implemented after the main baking process. The post-treatment step is a step performed for use as a phosphor. After the main firing step, an annealing treatment is performed for forming a final crystal structure in an air atmosphere at 1100 ° C. to 1500 ° C. for 4 hours according to the desired light emission characteristics. After that, a reduction treatment is performed to reduce Eu ³⁺ to Eu ²⁺ ions at 1200 ° C. in 97% Ar-3% H ₂ reducing gas for 3 hours. The annealing treatment in the post-treatment process of this example (sample number # 15) and the comparative example (# 115) was performed at 1200 ° C.

<Example 2-2> In the case of a barium-based ceramic phosphor The inventor is working on firing production (synthesis) with a new base material by controlling the composition and crystal structure of the barium-based ceramic phosphor.
Compositional formula (Ba _1-x Eu _x ) _0.79 (A
l _1-y Zn _y ) _10.9 O _17.14- δ (where 0.01 ≦ x ≦ 0.2 and 0 ≦ y ≦ 0.1), the blue barium-based ceramic phosphor is a raw material in the solid phase method. After the mixed powder to be formed is molded and the compact is temporarily fired, the main firing step is performed, and then the post-processing step is performed. When performing the main firing step in an air atmosphere, for homogeneous firing in which the average grain size of the crystal grains reaches 2 to 5 μm, pulverization / mixing using a planetary ball mill is performed at 1200 ° C. many times. It is necessary to repeat pulverization / mixing and firing (Non-patent Document 2). However, according to the crystalline oxide ceramics short-time firing method of the present invention, the atmospheric atmosphere has hitherto been produced by firing in a pressurized gas atmosphere having an absolute pressure of 0.35 MPa and a firing time of 2 hours. Below, pulverization and mixing and firing were repeated in an electric furnace, and the same crystal grain homogeneity as that obtained by firing for a total of 50 hours in the main firing step could be obtained.

FIG. 13 shows that the blue barium ceramic phosphor having x = 0.1 and y = 0.01 was repeatedly pulverized and mixed and fired while confirming the XRD pattern until it became a homogeneous phase, and was 1200 ° C. in an air atmosphere. At the main baking temperature, after baking for a total baking time of 50 hours, the post-processing step (sample number # 116) and the crystalline oxide ceramics short-time baking according to the present invention The XRD pattern of the production method (sample number # 16) produced by performing a post-treatment process after firing at a main firing temperature of 1100 ° C. in a pressurized gas atmosphere with an absolute pressure of 0.35 MPa for 2 hours. FIG.
The peak angle positions and the relative intensities of the peaks found in the XRD patterns of Sample No. # 116 and Sample No. # 16 are almost the same, and the main firing step was performed by the crystalline oxide ceramic short-time firing method of the present invention. It can be seen that the sample (sample number # 16) and the sample subjected to the main baking step for a long time in the air atmosphere (sample number # 116) are substantially equivalent in the regularity of the crystal structure of the crystal grains.

In addition, before the main baking step at the above main baking temperature, a preliminary baking step was performed in which the contained gas components and the like were sufficiently skipped at 700 to 800 ° C. for several hours in the air atmosphere. Further, in the main firing step, a reaction is formed in which a parent phase crystal structure formed by the reaction of CaO and SiO ₂ is substituted with Zn ions and Eu ions as an activator (emission center ion) as a solid solution. Is happening. Furthermore, the post-processing process was implemented after the main baking process. The post-processing step is a step performed for use as a phosphor. After the main baking step, an annealing treatment is performed for forming a final crystal structure in an air atmosphere at 1500 ° C. to 1600 ° C. for 4 hours according to the desired light emission characteristics. After that, a reduction treatment is performed to reduce Eu ³⁺ to Eu ²⁺ ions at 1200 ° C. in 97% Ar-3% H ₂ reducing gas for 3 hours. The annealing treatment in the post-treatment process of the present example (sample number # 16) and the comparative example (# 116) was performed at 1550 ° C.

<Example 3: Flow chart of typical series of steps>
FIG. 14 is a flow chart of a typical series of steps of the crystalline oxide ceramic short-time firing method and optional post-treatment step according to the present invention.
In step S1, an oxide and / or carbonate and / or phosphate powder of an element other than oxygen contained in the crystalline oxide ceramic to be baked and manufactured, the average particle size of which is a reference powder particle size The following powders are mixed to obtain a mixed powder. The reference powder particle size can be selected from 0.1 to 0.3 μm, for example 0.2 μm. In step S2, the mixed powder is molded into a molded body. Step S3 is a pre-baking step of pre-baking the obtained molded body. Pre-baking is usually performed at a temperature of 500 to 850 ° C., for example, in an air atmosphere.

Steps S4 and S5 represent the main firing step in the present invention. In step S4, the compressed air is used and the absolute pressure is included in the preferred absolute pressure section, for example, at a main firing temperature of less than 1200 ° C., for example, 1000 to 1100 ° C. in a pressurized gas atmosphere of 0.33 to 0.38 MPa, for example. Then, a main firing step is performed in which the average grain size of the crystal grains reaches the target crystal grain size. The target crystal grain size is usually 2 to 3 μm in the case of crystalline oxide ceramics for phosphors.
Although it is selected as m or more, other values may be used depending on the application. In step S5, it is determined whether or not the average grain size of the crystal grains has reached the target crystal grain size. If YES, the process proceeds to step S6, and if NO, the process returns to step S4 to perform the main firing step. Will continue. In addition, since it is difficult to measure the average grain size of the sample crystal grains in real time, the growth rate of the average grain size of the crystal grains according to the firing conditions is examined in advance, and based on the elapsed time from the start of the main firing step. Whether or not the average grain size of the crystal grains has reached the target crystal grain size may be determined in step S5. Alternatively, the relationship between the growth of the average grain size of the crystal grain and the feature appearing in the XRD pattern diagram, TEM diffraction image diagram, or SEM photograph diagram is examined in advance, and the average grain size of the crystal grain is determined based on the feature. It may be determined in step S5 whether or not the crystal grain size is reached.
In step S6, it is determined whether or not to perform the post-processing step based on the type and application of the crystalline oxide ceramics. If YES, the process proceeds to step S7, and if NO, the process proceeds to step S8. In step S7, a post-processing process is performed. For example, in the case of a phosphor, the post-treatment process is an annealing treatment or a reduction treatment according to the required light emission characteristics.
In step S8, all processes are completed.

The fired body, which is the crystalline oxide ceramic produced using the crystalline oxide ceramic short-time firing method of the present invention, may or may not be used as a powder depending on its use. In the former case, the fired body is pulverized to particles having a particle size of 1 to 5 μm and used as a powder. In that case, the powder basically consists of uniformly grown crystal grains. In the latter case, the fired body is used as it is or after being cut into a plurality of pieces. In the case of phosphor applications, there can be both usage aspects.
In addition, the fired body that has completed the firing process may be pulverized into a powder, and a post-treatment process may be performed on the powder.

<Example 4: Apparatus for carrying out firing method>
FIG. 15 is a schematic cross-sectional view of an apparatus 1 for carrying out the crystalline oxide ceramic short-time firing method according to the present invention. The apparatus 1 includes a firing furnace 10 that can be kept airtight, and a firing furnace 10. A holding unit 2 for holding a workpiece 3 which is a mixed powder or a molded body thereof, a heating unit 4 such as a heating element, a pressurized gas introducing unit 5, a gas discharging unit 6, and a pressure gauge. 7 and a control unit 8.
The firing furnace 10 has a furnace wall 15, and the inner surface of the furnace wall 15 is covered with a heat insulating member 16. The pressurized gas introducing means 5 includes a compressor 52 that compresses a mixed gas containing oxygen and supplies a pressurized gas, a gas introducing pipe 51 that communicates air between the compressor 52 and the inside of the firing furnace 10, and a gas introducing pipe 51. The gas introduction valve 53 provided in the middle is included. The gas discharge means 6 includes an exhaust pipe 61, an exhaust valve 63 provided in the middle of the exhaust pipe 61, and an optional exhaust processing unit 62. One end of the exhaust pipe 61 communicates with the inside of the firing furnace 10 and the other end of the exhaust pipe 61 is connected to the exhaust processing unit 62. The exhaust processing unit 62 renders the gas sent through the exhaust pipe 61 harmless if necessary and releases it to the atmosphere. The exhaust pipe 61 is provided with a pressure gauge 7 at a portion between the firing furnace 10 and the exhaust valve 63 so that the pressure of the gas inside the firing furnace 10 can be measured.
A heating means 4 such as a heating element is provided on the inner surface of the furnace wall 15 covered with the heat insulating member 16, and the gas inside the firing furnace 10 can be heated. Further, a part of the outer surface of the gas introduction pipe 51 and the exhaust pipe 61 may be covered with the heat insulating member 16, and in addition, a heating means is provided so as to cover part of the outer surface of the gas introduction pipe 51 and the exhaust pipe 61 4 may be provided. The heating means 4 may not only heat the gas inside the firing furnace 10 but also heat the workpiece 3 using radiation of electromagnetic waves such as infrared rays and microwaves. The heating means 4 can heat the gas inside the firing furnace 10 and the object to be processed to a temperature of at least 1000 to 1100 ° C., or 1000 ° C. or more and less than 1200 ° C., and preferably the annealing temperature in the post-processing step It is desirable that it can be heated to a temperature of 1100 to 1500 ° C or 1500 to 1600 ° C.

FIG. 16 is an explanatory diagram of the control unit 8 of the crystalline oxide ceramic short-time firing apparatus according to the present invention. The control unit 8 includes a central processing unit (CPU) 81, a storage unit 82 such as a memory or a hard disk drive, an input unit 83, and a display unit 84 such as a display, and includes a pressure gauge 7, a temperature sensor 9, and a heating unit 4. The compressor 52, the gas introduction valve 53, and the exhaust valve 63 are connected by a communication line.
The control unit 8 transmits the pressure of the gas in the firing furnace 10 transmitted from the pressure gauge 7, the temperature of the workpiece 3 or the gas in the firing furnace 10 transmitted from the temperature sensor 9, and a timer (not shown). The elapsed time calculated from the time at which the firing is performed, and the firing temperature and the pressure of the gas in the firing furnace 10 previously stored in the storage means 82, or the firing temperature and the firing furnace 10 that are previously stored in the storage means 82 Based on the fluctuation profile of the gas pressure, the heating means 4, the compressor 52, the introduction valve 53, and the exhaust valve 63 are controlled to determine the gas pressure in the firing furnace 10 and the object 3 or the firing furnace 10. Program control to automatically adjust the gas temperature.

  The present invention is not limited to the above-described embodiment, and various modifications, design changes, and other examples within the scope not departing from the technical idea of the present invention are included in the technical scope. Not too long.

Crystalline oxide ceramics are widely used in industry as phosphor materials for white LEDs and displays.
The crystalline oxide ceramics short-time firing method of the present invention is a conventional method for firing materials in an atmospheric atmosphere using an electric furnace, and for materials that have taken a long time to manufacture, in a pressurized gas atmosphere of optimum absolute pressure. By carrying out the baking, the main baking step is completed at a low main baking temperature and in a short time of a quarter or less of the conventional one, thereby realizing growth of an average grain size of uniform crystal grains. Therefore, it is possible to greatly reduce the labor and time of manufacturing, and it is not only advantageous in terms of cost because it does not require a sintering aid, but the number of parameters involved in the manufacturing process is small. It has the advantage of being easy to optimize. The manufacturing method and manufacturing apparatus of the present invention have wide industrial applicability.

DESCRIPTION OF SYMBOLS 1 Firing furnace 2 Holding part 3 To-be-processed object 4 Heating means 5 Pressurized gas introduction means 6 Gas discharge means 7 Pressure gauge 8 Control part 9 Temperature sensor 11 Crystal grain 12 Pore 15 Furnace wall 16 Thermal insulation member 21 Periodic interval 31 Lithium niobate XRD pattern 32 XRD pattern 33 satellite peak 34 satellite peak 51 gas introduction pipe 52 compressor 53 gas introduction valve 61 exhaust pipe 62 exhaust treatment part 63 exhaust valve 81 CPU
82 storage means 83 input means 84 display section

Claims (12)

This is a method for producing crystalline oxide ceramics by firing. The average grain size of the crystal grains at a main firing temperature of less than 1200 ° C. in a pressurized gas atmosphere in which the absolute pressure is included in the preferred absolute pressure section using compressed air. Including a main baking step of baking until the diameter reaches a target crystal grain size, and the time required for the main baking step is less than a quarter of that required when the main baking step is performed in an air atmosphere. The crystalline oxide ceramic is represented by the composition formula Li _{1 + xy} Nb _1-x-3y Ti _{x + 4y} O ₃ (where 0.07 ≦ x ≦ 0.33 and 0 ≦ y ≦ 0.175), and is constant. A crystalline oxide ceramic short-time firing method, characterized in that it is an LNT ceramic with a superstructure having a periodic interval of This is a method for producing crystalline oxide ceramics by firing. The average grain size of the crystal grains at a main firing temperature of less than 1200 ° C. in a pressurized gas atmosphere in which the absolute pressure is included in the preferred absolute pressure section using compressed air. Including a main baking step of baking until the diameter reaches a target crystal grain size, and the time required for the main baking step is less than a quarter of that required when the main baking step is performed in an air atmosphere. The crystalline oxide ceramic has a composition formula (Ca _{2−x / 2−y} Eu _y □ _{x / 2} ) (Si _1−x P _x ) O ₄ (where 0 ≦ x ≦ 0.20 and 0.02). A crystalline oxide ceramic short-time firing method, characterized in that it is a silicate ceramic phosphor represented by ≦ y ≦ 0.5) . A method for producing crystalline oxide ceramics by firing, wherein compressed grains are used, and a crystal grain is formed at a firing temperature of less than 1200 ° C. under a pressurized gas atmosphere in which the absolute pressure is included in a preferred absolute pressure section.
Compared with the case where the main baking step is performed in an air atmosphere, the time required for the main baking step is a quarter of that of the main baking step. The crystalline oxide ceramic has a composition formula (Ba _1-x Eu _x ) _0.79 (Al _1-y Zn _y ) _10.9 O _17.14-δ (where 0.01 ≦ x ≦ 0.2 and 0 ≦ y ≦ 0.1) A crystalline oxide ceramic short-time firing method, characterized in that the phosphor is a barium-based ceramic phosphor. Prior to the main firing step, a mixed powder obtained by mixing oxide and / or carbonate and / or phosphate powders of elements other than oxygen contained in the crystalline oxide ceramics is formed. The crystalline oxide ceramics short time baking manufacturing method in any one of Claims 1-3 including the temporary baking process which pre-fires the obtained molded object. 5. The crystalline material according to claim 1, wherein the preferred absolute pressure section is 0.33 to 0.38 MPa, the main firing temperature is 1000 to 1100 ° C., and the target crystal grain size is 2 to 5 μm. Oxide ceramics short-time firing method. The crystalline oxide ceramic is the LNT ceramic, and the mixed powder is a mixed powder obtained by mixing LiCO ₃ , Nb ₂ O ₅ , and TiO ₂ powders, and the superstructure is formed by diffusion of Ti atoms. The crystalline oxide ceramic short-time firing method according to claim 4 or 5 , wherein the method is a periodic structure. 7. The crystalline oxide ceramics according to claim 6 , wherein when the composition of the LNT ceramic is changed in a range of Ti concentration of 15 to 30 mol%, the constant period interval of the superstructure is narrowed as the Ti concentration is increased. Firing method. The mixed powder contains a total of 0.5 to 5 % by mass of RE ₂ O ₃ powder, and the LNT ceramic is a crystalline oxide ceramic activated by RE, and the RE is a rare earth element Dy, Er, Eu. The crystalline oxide ceramics short-time firing method according to claim 6 or 7 , which is one or more elements of Nd, Pr, Sm, Tm, Tb, and Yb. The crystalline oxide ceramic is the silicate ceramic phosphor, and the mixed powder is a mixed powder obtained by mixing powders of CaCO ₃ , SiO ₂ , CaHPO ₄ .2H ₂ O, and Eu ₂ O ₃ , Including a post-treatment step performed after the main firing step, in which the annealing treatment is performed in an air atmosphere, and further, a reduction treatment is performed in which Eu ³⁺ ions are reduced to Eu ²⁺ ions in a reducing gas. The crystalline oxide ceramics short time baking manufacturing method of Claim 4 or 5 . The crystalline oxide ceramic is the barium-based ceramic phosphor, and the mixed powder is a mixed powder obtained by mixing powders of BaCO ₃ , Al ₂ O ₃ , ZnO, and Eu ₂ O ₃ , and the main firing step. includes a post-treatment step more is performed later, in the post-treatment step, annealing is performed in an air atmosphere, further, subjected to reduction processing for reducing the Eu ³⁺ ions Eu ²⁺ ions in a reducing gas, according to claim 4 Or the crystalline oxide ceramics short time baking manufacturing method of 5. It is an apparatus for implementing the crystalline oxide ceramics short time baking manufacturing method in any one of Claims 1-10 , It arrange | positions in the said baking furnace and it becomes a raw material arrange | positioned in the said baking furnace A holding unit for holding the mixed powder or a molded body thereof, a heating unit, a pressurized gas introduction unit that pressurizes and feeds a mixed gas containing oxygen into the firing furnace, and releases the gas in the firing furnace to the outside. A crystalline oxide ceramic short-time firing apparatus having at least a gas discharge means. The crystalline oxide ceramics according to claim 11 , comprising a timer, and a control unit that performs program control for automatically adjusting the temperature of the mixed powder or the molded body and the pressure of the gas in the firing furnace. Short-time firing device.