WO2023238861A1 - ジルコニア焼結体とその製造方法 - Google Patents

ジルコニア焼結体とその製造方法 Download PDF

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WO2023238861A1
WO2023238861A1 PCT/JP2023/020999 JP2023020999W WO2023238861A1 WO 2023238861 A1 WO2023238861 A1 WO 2023238861A1 JP 2023020999 W JP2023020999 W JP 2023020999W WO 2023238861 A1 WO2023238861 A1 WO 2023238861A1
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Prior art keywords
sintered body
zirconia
heating
zirconia sintered
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French (fr)
Japanese (ja)
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瑛 川合
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Hitachi Construction Machinery Co Ltd
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KCM Corp
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Priority to US18/869,069 priority Critical patent/US12497333B2/en
Priority to JP2024524565A priority patent/JP7523724B2/ja
Publication of WO2023238861A1 publication Critical patent/WO2023238861A1/ja
Priority to JP2024070618A priority patent/JP7523710B1/ja
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Priority to US19/381,637 priority patent/US20260062354A1/en
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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
    • A61K6/00—Preparations for dentistry
    • A61K6/80—Preparations for artificial teeth, for filling teeth or for capping teeth
    • A61K6/802—Preparations for artificial teeth, for filling teeth or for capping teeth comprising ceramics
    • A61K6/818—Preparations for artificial teeth, for filling teeth or for capping teeth comprising ceramics comprising zirconium oxide
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
    • C04B35/48—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on zirconium or hafnium oxides, zirconates, zircon or hafnates
    • C04B35/486—Fine ceramics
    • C04B35/488—Composites
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61C—DENTISTRY; APPARATUS OR METHODS FOR ORAL OR DENTAL HYGIENE
    • A61C13/00—Dental prostheses; Making same
    • A61C13/08—Artificial teeth; Making same
    • A61C13/083—Porcelain or ceramic teeth
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61C—DENTISTRY; APPARATUS OR METHODS FOR ORAL OR DENTAL HYGIENE
    • A61C7/00—Orthodontics, i.e. obtaining or maintaining the desired position of teeth, e.g. by straightening, evening, regulating, separating, or by correcting malocclusions
    • A61C7/12—Brackets; Arch wires; Combinations thereof; Accessories therefor
    • A61C7/14—Brackets; Fixing brackets to teeth
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    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
    • C04B35/48—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on zirconium or hafnium oxides, zirconates, zircon or hafnates
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    • C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/626—Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B
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    • C04B2235/32—Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
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    • C04B2235/32—Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
    • C04B2235/3224—Rare earth oxide or oxide forming salts thereof, e.g. scandium oxide
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    • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
    • C04B2235/65—Aspects relating to heat treatments of ceramic bodies such as green ceramics or pre-sintered ceramics, e.g. burning, sintering or melting processes
    • C04B2235/656—Aspects relating to heat treatments of ceramic bodies such as green ceramics or pre-sintered ceramics, e.g. burning, sintering or melting processes characterised by specific heating conditions during heat treatment
    • C04B2235/6565—Cooling rate
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    • C04B2235/66—Specific sintering techniques, e.g. centrifugal sintering
    • C04B2235/661—Multi-step sintering
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    • C04B2235/661—Multi-step sintering
    • C04B2235/662—Annealing after sintering
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Definitions

  • the present invention relates to a zirconia sintered body and a method for manufacturing the same.
  • This application claims priority based on Japanese Patent Application No. 2022-094106 filed on June 10, 2022 and Japanese Patent Application No. 2023-031663 filed on March 2, 2023. , the entire contents of which are incorporated herein by reference.
  • Zirconia sintered bodies with a small amount of yttria (Y 2 O 3 ) dissolved in solid solution are used as dental materials (for example, dentures) due to their high strength, toughness, and aesthetics. It is widely used as a biomaterial for products such as dental prosthetics, denture mill blanks, orthodontic brackets), etc.
  • Patent Document 1 discloses a translucent zirconia sintered body containing more than 4.0 mol% and 6.5 mol% of yttria and less than 0.1 wt% of alumina. This zirconia sintered body has a high sintered body density and excellent translucency, so it is said to have both translucence and strength particularly suitable for a denture for front teeth.
  • Patent Documents 2 and 3 disclose that by setting the sintering temperature of the zirconia sintered body to at least 1350° C. or lower, a zirconia sintered body with excellent hydrothermal deterioration resistance can be realized.
  • molded object or "workpiece” containing partially stabilized zirconia containing yttria and/or ytterbia (Yb 2 O 3 ) in a predetermined proportion. It was discovered that a zirconia sintered body with excellent translucency and hydrothermal deterioration resistance can be realized by sintering a zirconia sintered body (also referred to as zirconia) by microwave heating and then rapidly cooling it to 1300°C.
  • zirconia sintered body also referred to as zirconia
  • a zirconia sintered body having excellent translucency and hydrothermal deterioration resistance can be manufactured.
  • the heating method of the microwave heating is multi-mode. Thereby, heating can be performed while suppressing the generation of plasma. As a result, the occurrence of cracks in the zirconia sintered body is suppressed, and a zirconia sintered body with excellent translucency and hydrothermal deterioration resistance can be manufactured.
  • the microwave heating is performed in an oxidizing atmosphere in the second heating step.
  • the microwave heating is performed in an atmosphere with an oxygen concentration of 30 vol% or more and 100 vol% or less. This effectively prevents the zirconia sintered body from darkening, making it possible to produce a zirconia sintered body that is more aesthetically pleasing and has excellent translucency and hydrothermal deterioration resistance. .
  • SiC susceptors are placed at positions that sandwich the object to be processed from both sides in a predetermined direction. Thereby, the sintering inside the object to be processed can proceed more suitably, so that a zirconia sintered body with excellent translucency and hydrothermal deterioration resistance can be manufactured.
  • the zirconia includes granular particles. This improves shape stability and improves handling and workability.
  • the present disclosure provides a zirconia sintered body.
  • This zirconia sintered body can be manufactured, for example, by any of the manufacturing methods described above.
  • the zirconia sintered body disclosed herein is a zirconia sintered body containing zirconia, yttria, and ytterbia, and when the total of zirconia, yttria, and ytterbia is 100 mol%, yttria and ytterbia are The total proportion of is 4 mol% or more and 6 mol% or less, and the coefficient of variation of the characteristic X-ray intensity of yttrium or ytterbium measured by line analysis using EPMA is 0.04 or less. According to this configuration, excellent light transmittance and hydrothermal deterioration resistance can be achieved.
  • the c/a axis length ratio of the unit cell is within the range of 1.0055 or more and less than 1.010 when the entire crystal phase is 100% by mass.
  • the proportion of crystalline phase is 40% by mass or more. This improves translucency and hydrothermal deterioration resistance.
  • the c/a axis length ratio of the unit cell of the zirconia sintered body and its ratio are determined by Rietveld analysis using RIETAN-FP as an analysis program for the profile of the X-ray diffraction pattern of the zirconia sintered body. You can get it by doing
  • the total light transmittance of a 1 mm thick test piece to a D65 light source in the thickness direction is 40% or more. As a result, a highly aesthetic zirconia sintered body is realized.
  • the proportion of monoclinic crystals after immersion in hot water at 140°C for 100 hours is 10% or less.
  • the zirconia sintered body disclosed herein can have such excellent hydrothermal deterioration resistance.
  • the c/a axis length ratio of the unit cell when the entire crystal phase is 100% by mass, the c/a axis length ratio of the unit cell is within the range of 1 or more and less than 1.0055.
  • the proportion of a certain crystalline phase is 25% by mass or less. According to such a configuration, the crystal phase becomes more homogeneous, so better light transmittance and hydrothermal deterioration resistance can be realized.
  • the zirconia sintered body further includes alumina, and the proportion of the alumina is 0.15% by mass or less when the entire zirconia sintered body is 100% by mass.
  • the present disclosure also provides a dental material containing the zirconia sintered body disclosed herein.
  • One preferred embodiment of the dental material disclosed herein is a denture, a denture mill blank, or an orthodontic bracket.
  • the zirconia sintered body disclosed herein has excellent translucency and hydrothermal deterioration resistance, and therefore can be suitably used as a dental material.
  • FIG. 1 is a flowchart outlining one aspect of the method for producing a zirconia sintered body disclosed herein.
  • FIG. 2 is a schematic diagram illustrating an example of a method of microwave heating a target object (temporary sintered body).
  • FIG. 3 is a graph showing the results of line analysis by EPMA of the surface of the zirconia sintered body of Example 2.
  • FIG. 4 is a graph showing the results of line analysis by EPMA of the surface of the zirconia sintered body of Example 4.
  • FIG. 5 is a graph showing the results of line analysis by EPMA of the surface of the zirconia sintered body of Example 7.
  • FIG. 6 is a graph showing the results of line analysis by EPMA of the surface of the zirconia sintered body of Example 8.
  • FIG. 1 is a flowchart outlining one aspect of the method for producing a zirconia sintered body disclosed herein.
  • FIG. 2 is a schematic diagram illustrating an example of a method of microwave heating a target object
  • FIG. 7 shows a mapping image (on the left) and a secondary electron image (on the right) of yttrium on the surface of the zirconia sintered body of Example 4.
  • FIG. 8 shows a mapping image (on the left) and a secondary electron image (on the right) of yttrium on the surface of the zirconia sintered body of Example 7.
  • FIG. 9 shows a mapping image (left side) and a secondary electron image (right side) of yttrium on the surface of the zirconia sintered body of Example 8.
  • the zirconia sintered body disclosed herein contains at least zirconia (ZrO 2 ). Further, this zirconia sintered body contains at least one of yttria (Y 2 O 3 ) and ytterbia (Yb 2 O 3 ). That is, the zirconia sintered body disclosed herein has an embodiment containing both yttria and ytterbia, an embodiment containing yttria but not ytterbia, and an embodiment containing ytterbia but not yttria.
  • the zirconia sintered body contains zirconia as a main component.
  • "containing zirconia as a main component” means that zirconia accounts for the largest proportion of the compounds constituting the zirconia sintered body.
  • the proportion of zirconia is, for example, 70% by mass or more, preferably 80% by mass or more, and more preferably 90% by mass or more.
  • a high proportion of zirconia can improve the strength, toughness, hydrothermal deterioration resistance, etc. of the zirconia sintered body.
  • Yttria and/or ytterbia contained in the zirconia sintered body may be contained, for example, as a part of partially stabilized zirconia (so-called stabilizer) partially dissolved in zirconia.
  • partially stabilized zirconia the proportion of monoclinic crystals is suppressed at room temperature, so that strength and toughness can be improved.
  • variations in the crystal phase constituting the zirconia sintered body are suppressed, so that the light transmittance can be improved.
  • the total proportion of yttria and ytterbia (in other words, the total of the stabilizer.
  • the elements not included are 0 mol%.
  • the same applies hereinafter) is, for example, 4 mol% or more, and may be 4.1 mol% or more.
  • the total proportion of such yttria and/or ytterbia may be, for example, 6 mol% or less, or 5.6 mol% or less.
  • the proportion of yttria may be greater than that of ytterbia, and the proportion of yttria may be less than that of ytterbia.
  • all of yttria and/or ytterbia may be dissolved in zirconia as a solid solution, or may include yttria and/or ytterbia in an undissolved state that is not dissolved in zirconia.
  • the zirconia sintered body may further contain alumina (Al 2 O 3 ). Since abnormal grain growth is suppressed in a zirconia sintered body containing alumina, the strength and translucency of the zirconia sintered body can be improved. Furthermore, since the low temperature deterioration resistance can be improved, the strength and translucency of the zirconia sintered body can be maintained for a long period of time. On the other hand, since alumina remains as an impurity inside the sintered body and acts as a light scattering factor, the alumina content should not be too high.
  • the content of alumina is preferably 0.15% by mass or less, for example, 0.125% by mass or less, 0.1% by mass or less, or 0.1% by mass or less, when the entire zirconia sintered body is 100% by mass. It can be up to .05% by weight.
  • the zirconia sintered body may contain a conventionally known coloring agent to the extent that the effects of the technology disclosed herein are not significantly impaired.
  • the colorant include transition metal elements, lanthanoid rare earth elements, and the like. Examples of such elements include iron, nickel, cobalt, manganese, niobium, praseodymium, neodymium, europium, gadolinium, and erbium.
  • the amount of the colorant may be, for example, 2% by mass or less, 1% by mass or less, and 0.5% by mass or less based on the entire zirconia sintered body.
  • the zirconia sintered body may contain elements that may be unavoidably mixed. Examples include hafnium, magnesium, silicon, titanium, and the like. The total content of these elements is preferably 2.5% by mass or less, more preferably 2% by mass or less, for example 1.8% by mass or less in terms of oxide, based on the entire zirconia sintered body. It would be good if it were.
  • FIG. 1 is a flowchart outlining one aspect of the method for producing a zirconia sintered body disclosed herein.
  • the method for manufacturing a zirconia sintered body disclosed herein includes a process object preparation step S10 of preparing a process object containing zirconia and yttria and/or ytterbia, and a first heating step S20 of heating the process object.
  • a second heating step S30 in which the object to be processed (hereinafter also referred to as "temporary sintered body") that has passed through the first heating step S20 is heated by microwave heating; and a cooling step in which the object to be processed that has undergone the second heating step is lowered in temperature.
  • Step S40 may be included.
  • the processing object preparation step S10 includes preparing a material constituting the processing object (hereinafter also referred to as “processing object material”) (hereinafter also referred to as “processing object material preparation step”), and preparing the processing object material. (hereinafter also referred to as “molding step”).
  • a zirconia raw material is prepared.
  • the zirconia raw material is not particularly limited, for example, a zirconium salt or a hydrate thereof can be used.
  • the zirconium salt include zirconium oxychloride, zirconium chloride, zirconium sulfate, and zirconium nitrate. These may be used alone or in combination of two or more.
  • a zirconia sol is prepared by preparing an aqueous solution of a zirconia raw material and performing a hydrolysis reaction.
  • the hydrolysis reaction can be carried out by adding an alkali metal hydroxide, an alkaline earth metal hydroxide, an ammonia aqueous solution, etc. to the aqueous solution.
  • an alkali metal hydroxide for example, lithium hydroxide, sodium hydroxide, potassium hydroxide, etc. can be used
  • the alkaline earth metal hydroxide for example, magnesium hydroxide, calcium hydroxide, etc. can be used. be able to.
  • yttria and/or ytterbia is mixed into the zirconia sol (ZrO 2 .nH 2 O) obtained by hydrolysis.
  • the raw material for yttria is a yttrium-containing compound that can be turned into yttria by firing.
  • Examples of the yttrium-containing compound include yttrium chloride and yttrium nitrate.
  • the raw material for ytterbium may be a ytterbium-containing compound that can be turned into ytterbium by firing.
  • the ytterbium-containing compound include ytterbium chloride and ytterbium nitrate.
  • the ratio of yttria and/or ytterbia to be mixed may be the same as the ratio of yttria and/or ytterbia in the zirconia sintered body described above.
  • the total proportion of yttria and ytterbia is, for example, 4 mol% or more, even if it is 4.1 mol% or more. good.
  • the upper limit of the total proportion of yttria and ytterbia is, for example, 6 mol% or less, and may be 5.6 mol% or less.
  • the amount of yttria and/or ytterbia obtained by firing these raw materials is within the range of the above-mentioned ratio of yttria and/or ytterbia. All you have to do is make it happen.
  • yttrium chloride (YCl 3 ) (X is a positive number)
  • X is a positive number
  • yttrium chloride may be mixed in twice the amount of substance.
  • a dry powder in which each raw material is homogeneously dispersed can be obtained.
  • the drying method is not particularly limited, and for example, natural drying, blow drying, hot air drying, drying by heating using a heating furnace, vacuum drying, suction drying, freeze drying, etc. can be appropriately selected.
  • a calcined powder containing yttria and/or ytterbia partially stabilized zirconia By calcining the powder obtained by drying, a calcined powder containing yttria and/or ytterbia partially stabilized zirconia can be obtained.
  • the calcination temperature is not particularly limited, but can be, for example, 800°C to 1200°C, preferably 1000°C to 1200°C.
  • the yttria raw material can be oxidized to yttria
  • the ytterbia raw material can be oxidized to ytterbia.
  • the heating device for calcination a conventionally known heating device can be used, and examples of the heating device include an electric furnace, a muffle furnace, a tunnel type heating furnace, a microwave firing furnace, and the like.
  • the pulverization method is not particularly limited, and, for example, pulverization can be performed using a known pulverizer (for example, a ball mill, etc.).
  • a ball mill it is preferable to use, for example, zirconia balls having a diameter of about 0.1 mm to 5 mm.
  • the powder after pulverization is sorted to a desired particle size.
  • zirconia powder with a desired particle size can be obtained using a mesh sieve, and the opening size of the mesh may be appropriately selected according to the desired particle size.
  • the preferred average particle size of the zirconia powder used as the material to be treated is, for example, 100 nm to 300 nm, more preferably 150 nm to 200 nm. If the average particle size is within this range, sinterability is high and strength and translucency can be improved.
  • average particle size refers to the particle size (D 50 ) corresponding to 50% cumulatively from the fine particle side in the volume-based particle size distribution measured by laser diffraction/light scattering method. say. For such measurement, for example, a particle size distribution measuring device LA950V2 (manufactured by Horiba, Ltd.) can be used.
  • the zirconia powder produced as described above mainly contains yttria and/or ytterbia partially stabilized zirconia particles.
  • the proportion of yttria and/or ytterbia partially stabilized zirconia particles in the zirconia powder is 50% by number or more, preferably 60% by number or more, 70% by number or more, 80% by number or more, 90% by number or more, 95% by number or more. It can be more than % by number.
  • the zirconia powder may include completely stabilized zirconia.
  • the zirconia powder may contain zirconia particles in which yttria and/or ytterbia are not solidly dissolved.
  • the zirconia powder may contain yttria particles and/or ytterbia particles.
  • zirconia powder as the material to be processed can be obtained, but the material to be processed is not limited to such zirconia powder.
  • an aluminum compound may be mixed with the zirconia powder.
  • the aluminum compound can be oxidized to alumina by heating in the first heating step S20 and/or the second heating step S30. Therefore, the amount of the aluminum compound to be mixed may be determined to match the alumina content in the zirconia sintered body described above, assuming that all the aluminum contained in the aluminum compound is oxidized to alumina.
  • alumina powder, alumina sol, hydrated alumina, aluminum hydroxide, aluminum chloride, aluminum nitrate, aluminum sulfate, etc. can be used. Note that it may be a slurry in which zirconia powder and an aluminum compound are dispersed in a solvent such as water. When a slurry is used, zirconia powder in which the aluminum compound is suitably dispersed can be obtained by drying the slurry.
  • the average particle size of the aluminum compound is preferably the same as or smaller than that of the zirconia powder.
  • the average particle size of the aluminum compound is, for example, preferably 300 nm or less, more preferably 200 nm or less, and may be 150 nm or less, 100 nm or less (for example, 20 nm to 50 nm).
  • the aluminum compound can be suitably dispersed in the zirconia powder. Therefore, alumina can be more uniformly distributed in the zirconia sintered body, and abnormal grain growth in the zirconia sintered body can be suitably suppressed.
  • the material to be processed can be suitably used in granule form as well as powder form.
  • the average particle size of the granular material to be treated is, for example, from 10 ⁇ m to 100 ⁇ m, and may be from 20 ⁇ m to 90 ⁇ m, or from 40 ⁇ m to 80 ⁇ m.
  • shape stability can be improved, and handling and workability can be improved.
  • by easing residual stress during molding it is possible to suppress the generation of hot spots caused by differences in powder density during microwave heating.
  • zirconia is sintered by heating with microwaves, even if the granules have a larger average particle size than the powder, the inside of the granules can be suitably heated.
  • the method for producing the granular molded body material is not particularly limited, but it can be produced, for example, by spray drying zirconia powder.
  • the zirconia powder may contain an aluminum compound and may further contain a binder.
  • a slurry is prepared by mixing zirconia powder and a dispersion medium (for example, water), and the slurry is sprayed onto droplets and dried to obtain a granular material to be processed. can.
  • the binder is preferably a component that burns through at the heating temperature in the first heating step or second heating step, which will be described later.
  • the binder include acrylic resins, epoxy resins, phenol resins, amine resins, alkyd resins, and cellulose polymers.
  • acrylic resins acrylic resins
  • epoxy resins epoxy resins
  • phenol resins phenol resins
  • amine resins alkyd resins
  • cellulose polymers Among these, it is preferable to include an acrylic resin.
  • acrylic resin By including the acrylic resin, the adhesion between zirconia powders increases, and zirconia granules can be suitably manufactured. Moreover, the shape stability of the molded object to be processed is increased, and the object to be processed can be stably held.
  • Acrylic resins include polymers containing alkyl (meth)acrylate as a main monomer (component accounting for 50% by mass or more of the total monomers), and secondary monomers that are copolymerizable with the main monomer and the main monomer. Examples include copolymers containing the following.
  • (meth)acrylate is a term meaning acrylate and methacrylate.
  • the binder content may be, for example, 10% by mass or less, and preferably 5% by mass or less, when the entire powder used for spray drying is 100% by mass. Furthermore, if the amount of binder is too small, the effect of the binder may be insufficient. Therefore, the binder content may be, for example, 0.5% by mass or more, and may be 1% by mass or more.
  • the method for molding the material to be processed is not particularly limited, and for example, pressure molding, injection molding, extrusion molding, casting molding, etc. can be employed.
  • pressure molding for example, cold isostatic pressing (CIP), hot isostatic pressing (HIP), etc. are preferably adopted.
  • CIP or HIP a processed object (molded object) with high homogeneity and high density can be manufactured.
  • the object to be processed is preliminarily sintered by heating the object to obtain a preliminarily sintered body.
  • Such heating may remove components such as moisture, binder, and impurities that may be contained in the object to be processed.
  • pre-sintering can reduce voids that may exist in the object to be processed, cracks that may occur during sintering due to high-temperature and high-speed heating can be suitably prevented.
  • Preliminary sintering can be carried out at a heating temperature of, for example, 800°C to 1200°C, preferably 1000°C to 1100°C.
  • the pre-sintering time may vary depending on the shape, size, composition, etc.
  • the object to be processed can be heated by a known method, and for example, a heating device such as a muffle furnace, an electric furnace, or a microwave firing furnace can be used.
  • a heating device such as a muffle furnace, an electric furnace, or a microwave firing furnace can be used.
  • the temperature increase rate in heating in the first heating step S20 is not particularly limited, but for example, it may be 100°C/h to 250°C/h until reaching 800°C, or a predetermined temperature (for example, 1000°C to 1200°C) ) can be set at 50°C/h to 150°C/h. This can prevent rapid sintering and suppress the occurrence of cracks.
  • the object to be processed (temporary sintered body) that has passed through the first heating step S20 is sintered by microwave heating to obtain a sintered product.
  • microwave heating By performing microwave heating, the inside of the pre-sintered body can be heated quickly, so the difference between the progress of sintering on the surface side of the pre-sintered body and the progress of sintering on the inside is small. Therefore, the voids inside the zirconia sintered body can be further reduced.
  • the microwave heating method is not limited to the following example.
  • FIG. 2 is a schematic diagram illustrating an example of a method of microwave heating a temporary sintered body. Note that the dimensional relationships (length, width, thickness, etc.) in FIG. 2 do not reflect the actual dimensional relationships. The directions of upward, downward, left, and right are indicated by arrows U, D, L, and R, respectively, in the figure. Here, the directions of top, bottom, left, and right are only determined for convenience of explanation, and do not limit the installation form.
  • the microwave heating device 10 has a partition wall 12 and a heating space 14.
  • a heat insulating container 20 is installed in the heating space 14, and a susceptor 40 and a temporary sintered body 50 are accommodated in the housing space 22 of the heat insulating container 20.
  • a gas supply machine 30 is connected to the housing space 22 of the heat insulating container 20 .
  • the radiation thermometer 60 is installed at a remote location outside the microwave heating device 10.
  • the microwave heating device 10 has a heating space 14 surrounded by partition walls 12.
  • the heating space 14 is a space that accommodates an object to be heated with microwaves.
  • the side wall, ceiling, and/or bottom wall of the heating space 14 has a microwave irradiation part, and can irradiate microwaves to the object accommodated in the heating space 14 to heat it. can.
  • the microwave only needs to have a frequency conventionally used for microwave heating, and for example, microwaves with a frequency of 0.3 GHz to 3 GHz (for example, 2.45 GHz) can be used.
  • the partition wall 12 insulates the heating space 14 of the microwave heating device 10 from the outside, and a commercially available microwave device can be used. Further, from the viewpoint of improving heat insulation properties, the heating space 14 side of the partition wall 12 may be lined with a heat insulating material.
  • the partition wall 12 is provided with a through hole 16 for measuring the temperature of an object within the heating space 14 .
  • the through hole 16 penetrates so as to connect the heating space 14 and the outside of the microwave heating device 10 .
  • the microwave heating device 10 having such a configuration, for example, ⁇ -Reactor EX or ⁇ -Reactor Mx manufactured by Shikoku Keizoku Kogyo Co., Ltd. can be used.
  • the heat insulating container 20 has a housing space 22 that can house the susceptor 40 and the temporary sintered body 50 therein.
  • the heat insulating container 20 has a gas introduction hole 24 for connecting the housing space 22 and the gas supply device 30, and a gas introduction hole 24 for communicating the housing space 22 and the heating space 14. It has a gas exhaust hole 26 and a through hole 28 for measuring the temperature of the object to be heated in the accommodation space 22.
  • the heat insulating container 20 is a rectangular box-shaped container, but its shape is not particularly limited, and may be, for example, cylindrical, prismatic, or the like.
  • the heat insulating container 20 is designed to be separable into a lid part and a case part, so that objects to be heated can be easily put in and taken out of the accommodation space 22. Designed.
  • the material of the heat insulating container 20 may be, for example, ceramic fiber such as alumina silica fiber.
  • the gas introduction hole 24 is a through hole that communicates the housing space 22 and the heating space 14, and is designed so that the pump 32 connected to the gas supply device 30 can be inserted therethrough. Thereby, a desired gas can be supplied to the housing space 22 and the atmosphere within the housing space 22 can be controlled.
  • the gas discharge hole 26 is a through hole that communicates the housing space 22 and the heating space 14, and is designed so that the housing space 22 is not sealed. This can prevent the oxygen in the accommodation space 22 from being consumed and the accommodation space 22 from becoming a reducing atmosphere as the firing of the temporary sintered body 50 progresses. Further, the gas discharge hole 26 can prevent the gas supplied from the gas introduction hole 24 from staying in the accommodation space 22 .
  • one gas exhaust hole 26 is provided, but a plurality (two or more) may be provided. Further, in this embodiment, the gas exhaust hole 26 is provided in a wall opposite to the wall in which the gas introduction hole 24 is provided, but the position of the gas exhaust hole 26 is not particularly limited.
  • the diameter of the gas discharge hole 26 is not particularly limited, but may be, for example, about 5 mm to 50 mm, or, for example, about 5 mm to 20 mm.
  • a through hole 28 that communicates the storage space 22 and the heating space 14 is provided on the upper side of the heat insulating container 20. Further, here, the through hole 28 and the through hole 16 of the microwave heating device 10 are arranged in a straight line. Thereby, the temperature of the object to be heated placed in the housing space 22 can be measured by the radiation thermometer 60 installed outside the microwave heating device 10.
  • the through hole 28 is not particularly limited as long as it has a size that allows the radiation thermometer 60 to measure the temperature of the heated object, but for example, the diameter of the through hole 28 is about 5 mm to 10 mm. be able to.
  • the gas exhaust hole 26 and the through hole 28 are provided, but even one through hole can perform the functions of both the gas exhaust hole 26 and the through hole 28 described above. In order to obtain this, a configuration may be adopted in which only one of them is provided.
  • the gas supply device 30 can supply a desired gas to the accommodation space 22 of the heat insulating container 20 via the pump 32, and can adjust the atmosphere of the accommodation space 22.
  • the gas supply device 30 can be changed as appropriate depending on the desired gas, and any commercially available gas supply device (for example, an oxygen supply device) can be used without particular limitation. Note that when adjusting the accommodation space 22 to an atmospheric atmosphere, a blower or the like may be employed as the gas supply device 30.
  • the microwave heating is performed in an oxidizing atmosphere.
  • the oxidizing atmosphere include an atmospheric atmosphere and an atmosphere having a higher oxygen concentration than the atmospheric atmosphere.
  • the oxygen concentration is 30 vol% or more, and may be, for example, 50 vol% or more, or 70 vol% or more. Under such an oxidizing atmosphere, darkening of the zirconia sintered body can be further suppressed.
  • the upper limit of the oxygen concentration in the atmosphere is not particularly limited, and the oxygen concentration can be 100 vol % or less, but if the oxygen concentration is too high, abnormal heating due to oxygen plasma may occur. Therefore, the oxygen concentration is preferably 95 vol% or less, more preferably 90 vol% or less, for example. Note that such control of the oxidizing atmosphere may be performed in the housing space 22 of the heat insulating container 20 in which the temporary sintered body 50 is installed.
  • the temporary sintered body 50 in order to control the oxidizing atmosphere, it is preferable to continue supplying the atmosphere or a gas containing the above oxygen concentration to the accommodation space 22 (specifically, the temporary sintered body 50). . Thereby, it is possible to suppress fluctuations in the atmosphere in the housing space 22 (for example, a decrease in oxygen concentration) due to firing. Further, as indicated by arrows in FIG. 2, the gas supplied from the gas supply device 30 flows into the accommodation space 22 and is then discharged from the gas discharge hole 26 and/or the through hole 28. By forming such an oxygen flow environment around the temporary sintered body 50, it is possible to suppress the occurrence of abnormal heating due to oxygen plasma.
  • the susceptor 40 is a heating auxiliary member that can improve the efficiency of microwave heating by efficiently converting microwave energy into thermal energy. Specifically, since the susceptor 40 becomes hotter more quickly than the temporary sintered body 50 by absorbing microwaves, it can assist in increasing the temperature of the temporary sintered body 50 through heat conduction. When the temporary sintered body 50 reaches a high temperature, the temporary sintered body 50 itself becomes easy to absorb microwaves, and can act as a microwave absorber. When the temporary sintered body 50 easily absorbs microwaves, the internal heating mechanism of the temporary sintered body 50 is easily promoted by microwave heating. As a result, sintering inside the temporary sintered body 50 is promoted, voids are less likely to remain inside, and a zirconia sintered body with excellent strength and translucency can be manufactured.
  • the susceptor 40 is preferably placed at a position sandwiching the pre-sintered body 50 from both sides in a predetermined direction before the microwave heating.
  • the susceptors 40 are arranged on both sides (i.e., the upper and lower sides) of the temporary sintered body 50 in the vertical direction (up and down direction), or on both sides of the temporary sintered body 50 in at least one horizontal direction. Examples include aspects in which the Thereby, the surfaces on both sides of the pre-sintered body 50 in the predetermined direction are heated by the susceptor 40, so that the microwave absorption efficiency of the pre-sintered body 50 can be increased in a shorter time.
  • the internal heating of the temporary sintered body 50 by microwave heating can be realized in a shorter time, so that the voids inside the zirconia sintered body can be further reduced.
  • the susceptor 40 is typically placed in contact with the surface of the temporary sintered body 50, there may be a gap between the susceptor 40 and the surface of the temporary sintered body 50. .
  • a gap is not particularly limited, it is, for example, preferably 3 mm or less, more preferably 2 mm or less, and even more preferably 1 mm or less.
  • the temporary sintered body 50 is not sealed by the susceptor 40.
  • the microwave is easily absorbed directly into the temporary sintered body 50 without being hindered by the susceptor 40. Therefore, the internal heating of the pre-sintered compact is more efficient than when the susceptor completely encloses the pre-sintered compact (for example, when the pre-sintered compact is installed inside a closed box-shaped susceptor). It can be induced from low temperature range. As a result, the number of pores remaining inside the zirconia sintered body can be reduced compared to the sintering mode caused by heat conduction from the surface. Furthermore, since the temporary sintered body 50 is not sealed by the susceptor 40, oxygen around the temporary sintered body 50 can be prevented from being consumed and a reducing atmosphere is created.
  • the susceptors 40 are not installed (open) on both sides of at least one direction different from the predetermined direction in which the susceptors 40 are arranged. This makes it easier for microwaves to be directly absorbed into the temporary sintered body 50, and internal heating can be induced from a lower temperature range and more uniformly. Furthermore, by providing one direction in which the susceptor 40 is not installed, the pre-sintered body 50 can be placed in the flow of gas supplied from the gas supply device 30, so that the surrounding area of the pre-sintered body 50 can be The atmosphere can be controlled more suitably.
  • a temporary sintered body 50 is sandwiched between two plate-shaped susceptors 40 from above and below, and the horizontal direction of the temporary sintered body 50 is covered by the susceptors 40. Not yet.
  • the susceptor 40 is not arranged in any horizontal direction of the temporary sintered body 50, microwaves are particularly easily absorbed into the temporary sintered body 50, and the zirconia sintered body with reduced internal voids is easily absorbed. It becomes easier to produce a body.
  • a SiC susceptor whose main component is silicon carbide (SiC) is preferably employed.
  • SiC susceptor whose main component is silicon carbide (SiC)
  • "containing SiC as a main component” refers to a compound constituting the susceptor 40 in which SiC accounts for 50% by mass or more.
  • the SiC susceptor include single crystal SiC, recrystallized SiC, reaction sintered SiC, nitride bonded SiC, oxide bonded SiC, and silicon carbide fiber.
  • recrystallized SiC and silicon carbide fibers which are materials with relatively high porosity, can be preferably used.
  • recrystallized SiC can be particularly preferably used because it has excellent heat resistance.
  • the microwave absorption efficiency may decrease in dense recrystallized SiC, so the porosity of recrystallized SiC may be, for example, 10% to 90%, preferably 10% to It is 30%.
  • the porosity can be measured by a conventionally known method, for example, by mercury porosimetry.
  • the thickness per sheet is preferably, for example, 1 mm to 4 mm, more preferably 2 mm to 3 mm. If the susceptor 40 is too thin, the strength of the susceptor may be reduced. Moreover, if the susceptor 40 is too thick, it will be difficult to heat the susceptor 40, and the rate of temperature increase may become slow. Therefore, within the above thickness range, the strength of the susceptor 40 and the rate of temperature increase of the susceptor 40 are well balanced. Thereby, the voids inside the zirconia sintered body can be reduced more suitably.
  • one plate-shaped susceptor 40 is arranged above and below the temporary sintered body 50, but in the case of a plurality of plate-shaped susceptors 40 (two or more),
  • the number is not particularly limited.
  • two or more susceptors 40 may be stacked on each of the upper and lower sides of the temporary sintered body 50.
  • different numbers of susceptors 40 may be used on the upper side and the lower side of the temporary sintered body 50.
  • the susceptor 40 is plate-shaped, but the susceptor 40 is not particularly limited as long as it is placed on both sides of the pre-sintered body 50 in a predetermined direction.
  • Examples include a box-shaped (for example, hexahedral shape) susceptor in which a pair of opposing surfaces are provided with through holes, a columnar susceptor (for example, cylindrical shape, prismatic shape), and the like.
  • the radiation thermometer 60 can measure the temperature of an object without contact. As shown in FIG. 2, in this embodiment, the radiation thermometer 60 is installed at a location away from the microwave heating device 10, and measures the surface temperature of the susceptor 40 above the temporary sintered body 50. There is.
  • the heating temperature in the microwave heating in the second heating step S30 and the temperature used to calculate the temperature decreasing rate in the cooling step S40 described below refer to the temperature measured by the radiation thermometer 60. Note that from the viewpoint of more accurately measuring temperature changes due to microwave heating, it is preferable to fix the radiation thermometer 60 at a predetermined position using a clamp or the like.
  • an OPTCTRF1MHSFVFC3 sensor manufactured by Optris (pseudo emissivity setting 1.0) can be used.
  • the microwave heating may be performed at, for example, 1600°C or higher (e.g., higher than 1600°C), preferably 1620°C or higher, more preferably 1650°C or higher, even more preferably 1700°C or higher (for example, higher than 1700°C), and 1720°C or higher.
  • the above is particularly preferable.
  • the mechanism is not particularly limited, by setting the microwave heating temperature to a high temperature of 1,600°C or higher, a dense sintered body with suppressed voids that may occur inside the zirconia sintered body can be manufactured. . Further, in the crystal phase of the zirconia sintered body, variations in the crystal phase can be reduced, and discontinuity in grain boundaries can be reduced.
  • microwave heating it is appropriate for microwave heating to be, for example, 2000°C or lower, 1900°C or lower, 1800°C or lower, 1750°C or lower. , or 1730°C or lower.
  • the holding time for microwave heating may be changed as appropriate depending on the shape, size, composition, etc. of the temporary sintered body 50, and may be, for example, about 1 minute to 20 minutes, or, for example, about 1 minute to 10 minutes. . Note that the holding time herein does not include the temperature rising time until the micro heating temperature is reached.
  • the heating method of microwave heating is not particularly limited, and for example, either single mode or multi-mode can be used, but multi-mode is preferably adopted.
  • single mode plasma may be generated in the temporary sintered body 50 depending on the arrangement position, size, etc. of the temporary sintered body 50, and cracks may occur in the zirconia sintered body.
  • multi-mode concentration of the electromagnetic field within the heating space 14 is suppressed, making it difficult to generate plasma. This can suppress the occurrence of cracks in the zirconia sintered body.
  • the temperature increase rate of microwave heating is not particularly limited, since it is appropriately changed depending on the shape, size, composition, etc. of the temporary sintered body. For example, if the total proportion of yttria and ytterbia in the zirconia sintered body is 4 mol% to 5 mol%, the temperature increase rate until reaching about 1000°C to 1150°C should be 500°C/min to 900°C/min. I can do it. Thereby, the zirconia sintered body can be manufactured in a shorter time. Further, it is preferable that the temperature increase rate is, for example, 20° C./min to 50° C./min until the temperature reaches about 1150° C. to 1200° C. thereafter.
  • the temperature increase rate can be set to, for example, 40°C/min to 100°C/min, preferably 40°C/min to 60°C/min.
  • the progress of sintering of the temporary sintered body can be appropriately controlled, and a zirconia sintered body with better translucency and hydrothermal deterioration resistance can be manufactured.
  • the temperature increase rate until reaching about 1100° C.
  • the temperature increase rate be set at, for example, 5° C./min to 50° C./min until the temperature reaches about 1250° C. to 1550° C. Further, it is preferable that the temperature increase rate thereafter until reaching approximately 1600°C to 2000°C is, for example, 40°C/min to 100°C/min, preferably 40°C/min to 60°C/min.
  • the shape of the temporary sintered body 50 is not particularly limited, but is preferably, for example, disc-shaped from the viewpoint of more uniform sintering using microwaves.
  • the thickness of the pre-sintered body 50 is, for example, preferably 0.5 mm to 10 mm, more preferably 0.5 mm to 2 mm. Within this range, sintering using microwaves can be efficiently performed while maintaining the strength of the temporary sintered body 50.
  • the maximum diameter of the temporary sintered body 50 is, for example, preferably 10 mm to 60 mm, more preferably 10 mm to 20 mm. Within this range, more uniform microwave sintering can be performed.
  • the cooling step S40 the object to be processed that has undergone the second heating step S30 is rapidly cooled to 1300°C.
  • the cooling step S40 is a step performed after the object to be processed, which has been subjected to microwave heating in the second heating step S30, is heated and maintained at a predetermined temperature (for example, 1600° C. to 2000° C.), and is typically , carried out continuously from microwave heating. Through such rapid cooling, the zirconia sintered body disclosed herein can be obtained.
  • the temperature decreasing rate when cooling the object to be processed to 1300°C is, for example, 50°C/min or more, preferably 100°C/min or more, and more preferably 200°C/min or more.
  • the upper limit of the temperature decreasing rate is not particularly limited, but may be, for example, 1000° C./min or less, or 500° C./min or less.
  • the cooling method is not particularly limited as long as it can achieve the temperature drop rate within the above range, but examples include controlling microwave irradiation, natural cooling, and blowing air. Note that in the cooling step S40, if the gas containing oxygen was being supplied from the gas supply device 30 in the second heating step S30, the supply of the gas may be continued or may be stopped.
  • the zirconia sintered body by stopping the supply of the gas while the temperature is decreasing, the zirconia sintered body can be more stably manufactured.
  • the "temperature fall rate" in the cooling step S40 refers to the average temperature fall rate from when the temperature starts to fall until it reaches 1300°C.
  • the object to be processed is sintered by microwave heating, it is possible to obtain a dense zirconia sintered body with few internal voids. Furthermore, by performing microwave heating, the temperature of the heating space itself of the microwave heating device does not become as high as that of the object to be processed and the susceptor, making it possible to rapidly cool the zirconia sintered body at the temperature reduction rate mentioned above. It is possible to increase the proportion of crystal phases in which the c/a axis length ratio of the unit cell is within the range of 1.0055 or more and less than 1.010. As a result, a zirconia sintered body with excellent translucency and hydrothermal deterioration resistance is realized.
  • the reason why excellent translucency and hydrothermal deterioration resistance are achieved is not particularly limited, but is presumed to be as follows.
  • the rate of temperature drop after sintering is slow, so the c/a axis length ratio of the unit cell exceeds 1.012 and is 1.017.
  • the yttrium concentration is locally segregated.
  • a crystal phase having a unit cell c/a axis length ratio of more than 1.012 and less than 1.017 (for example, a crystal phase having a unit cell c/a axis length ratio of more than 1.012 and less than 1.017) It is thought that the crystal structure precipitates as a tetragonal crystal, which is more homogeneous than before. A homogeneous crystal structure makes it difficult to induce hydrothermal deterioration and suppresses reflection and refraction of light at crystal interfaces.
  • microwave heating produces a highly dense zirconia sintered body with few voids, making it difficult for water to penetrate into the zirconia sintered body. From the above, it is presumed that the zirconia sintered body disclosed herein has excellent translucency and hydrothermal deterioration resistance.
  • the proportion of the crystal phase in which the c/a axis length ratio of the unit cell is within the range of 1.0055 or more and less than 1.010, when the entire crystal phase is 100% by mass. is, for example, 40% by mass or more, preferably 45% by mass or more, more preferably 50% by mass or more.
  • the upper limit of this proportion is not particularly limited, but may be 100% by mass or less, 80% by mass or less, and 60% by mass or less. The higher the proportion of such crystalline phase, the more the translucency and hydrothermal deterioration resistance tend to improve.
  • the zirconia sintered body disclosed herein includes a crystal phase in which the c/a axis length ratio of the unit cell is in the range of 1.0055 or more and less than 1.010, when the entire crystal phase is 100% by mass;
  • the total proportion of the crystal phase in the range of more than 1.012 and less than 1.017 is, for example, 75% by mass or more, preferably 85% by mass or more, more preferably 95% by mass or more, particularly preferably 98% by mass.
  • the content may be greater than or equal to 100% by mass. The higher the ratio, the more homogeneous the crystal structure can be, and therefore, more excellent translucency and hydrothermal deterioration resistance can be achieved.
  • the proportion of the crystal phase in which the c/a axis length ratio of the unit cell is within the range of 1 or more and less than 1.0055 is: For example, 25% by mass or less, more preferably 15% by mass or less, further preferably 5% by mass or less, particularly preferably 2% by mass or less, and even 0% by mass (not included or below the detection limit).
  • the lower this ratio is, the more the segregation of yttrium and/or ytterbium is suppressed, and the more excellent translucency and hydrothermal deterioration resistance can be realized.
  • segregation of yttrium or ytterbium is suppressed.
  • segregation of yttrium or ytterbium at the boundaries of crystal grains on the surface of the zirconia sintered body is suppressed.
  • the distribution of yttrium or ytterbium can be evaluated as the distribution of yttria or ytterbia.
  • the yttria or ytterbium is homogeneously dispersed.
  • the distribution of yttrium or ytterbium can be evaluated, for example, by line analysis using a field emission electron beam microanalyzer (FE-EPMA).
  • FE-EPMA field emission electron beam microanalyzer
  • the coefficient of variation (CV) of the characteristic X-ray intensity of yttrium or ytterbium measured by line analysis using FE-EPMA is, for example, 0.04 or less, 0.035 or less, 0. It is .031 or less, or 0.02 or less.
  • the coefficient of variation is calculated based on the average value of five characteristic X-ray intensity data.
  • the coefficient of variation is the standard deviation divided by the arithmetic mean.
  • the above-mentioned line analysis is performed on the surface of a mirror-polished zirconia sintered body. Further, the measurement region of the line analysis is set so as to pass through the crystal interface of the zirconia sintered body at least once (preferably twice or more).
  • the proportion of monoclinic crystals after a hydrothermal deterioration test in which the body is immersed in hot water at 140°C for 100 hours is, for example, 10% or less, preferably 5% or less, or more. It is preferably 3% or less, particularly preferably 1% or less.
  • the hydrothermal deterioration test is conducted by immersing a zirconia sintered body with a mirror-polished surface in hot water at 140°C for 100 hours using a high-pressure microreactor (MMS-500, manufactured by O-M Labotech). I can do it.
  • the proportion of monoclinic crystal can be measured by obtaining an X-ray diffraction pattern of the polished surface of the zirconia sintered body after the hydrothermal deterioration test.
  • the zirconia sintered body disclosed herein has, for example, a total light transmittance of 40% or more, 42% or more, 44% or more, 45% or more, 46% or more, or 47% or more. If the total light transmittance is 40% or more, the excellent aesthetics required for the dental material can be achieved, for example, when the zirconia sintered body is used as the dental material. Further, although not particularly limited, the total light transmittance may be, for example, 60% or less. In this specification, the term "total light transmittance" refers to the total light transmittance of a 1 mm thick disk-shaped test piece with respect to a D65 light source in the thickness direction.
  • the zirconia sintered body disclosed herein has both excellent translucency and excellent resistance to hydrothermal deterioration, so it can be suitably used, for example, as a dental material.
  • dental materials include dentures such as dentures for front teeth and dentures for back teeth, denture mill blanks, orthodontic brackets, dental prostheses, and bridges.
  • Item 1 A method for producing a zirconia sintered body, including the following steps: A treated object containing zirconia, yttria and/or ytterbia, where the total proportion of yttria and ytterbia is 4 mol% or more and 6 mol% or less, when the total of zirconia, yttria, and ytterbia is 100 mol%.
  • a processing object preparation step for preparing a certain processing object; a first heating step of heating the object to be processed at a temperature of 800°C or more and 1200°C or less; a second heating step of heating the object to be processed that has undergone the first heating step at a temperature of 1,600° C. or more and less than 2,000° C. by microwave heating; and A method for producing a zirconia sintered body, which includes a cooling step in which the temperature is lowered to 1300°C.
  • Item 2 The manufacturing method according to item 1, wherein the heating method of the microwave heating is multimode.
  • Item 3 The manufacturing method according to item 1 or 2, wherein in the second heating step, the microwave heating is performed in an oxidizing atmosphere.
  • Item 4 The manufacturing method according to Item 3, wherein in the second heating step, the microwave heating is performed in an atmosphere having an oxygen concentration of 30 vol% or more and 100 vol% or less.
  • Item 5 The manufacturing method according to any one of items 1 to 4, wherein in the second heating step, SiC susceptors are placed at positions that sandwich the object to be processed from both sides in a predetermined direction.
  • Item 6 The manufacturing method according to any one of Items 1 to 5, wherein in the process of preparing the object to be processed, the object to be processed is prepared by molding granules containing zirconia.
  • Item 7 A zirconia sintered body containing zirconia and yttria and/or ytterbia, When the total of zirconia, yttria, and ytterbia is 100 mol%, the total proportion of yttria and ytterbia is 4 mol% or more and 6 mol% or less, The coefficient of variation of the characteristic X-ray intensity of yttrium or ytterbium measured by line analysis by EPMA is 0.04 or less, Zirconia sintered body.
  • Item 8 When the entire crystalline phase is 100% by mass, the proportion of the crystalline phase in which the c/a axis length ratio of the unit cell is within the range of 1.0055 or more and less than 1.010 is 40% by mass or more.
  • Item 9 The zirconia sintered body according to Item 7 or 8, wherein the total light transmittance for a D65 light source in the thickness direction of a test piece having a thickness of 1 mm is 40% or more.
  • Item 10 The zirconia sintered body according to any one of Items 7 to 9, wherein the proportion of monoclinic crystals after being immersed in hot water at 140° C. for 100 hours is 10% or less.
  • Item 11 When the entire crystalline phase is 100% by mass, the proportion of the crystalline phase in which the c/a axis length ratio of the unit cell is within the range of 1 or more and less than 1.0055 is 25% by mass or less.
  • Item 12 The zirconia sintered body according to any one of Items 7 to 11, further containing alumina and having a proportion of alumina of 0.15% by mass or less when the entire zirconia sintered body is 100% by mass. Concretion.
  • Item 13 A dental material comprising the zirconia sintered body according to any one of Items 7 to 12.
  • Item 14 The dental material according to Item 13, which is a denture, a denture mill blank, or an orthodontic bracket.
  • Yttria was mixed into a zirconia sol produced by hydrolyzing a zirconium oxychloride solution. At this time, yttria was set to be 4.1 mol% of the total of zirconia and yttria. After drying the mixture, it was calcined at 1120° C. for 4 hours to obtain partially stabilized zirconia powder.
  • the zirconia powder was pulverized in a ball mill using zirconia balls with a diameter of 1 mm, and then sorted through a mesh sieve to obtain a zirconia powder with an average particle size of 150 nm to 200 nm as a molded body material.
  • alumina powder with an average particle size of 30 nm was mixed with zirconia powder to prepare zirconia powder containing 0.05% by mass of alumina.
  • This zirconia powder was filled into a disk-shaped mold and a pressure of 0.78 MPa was applied, and then the molded body was taken out from the mold and CIP molded at 196 MPa. Thereafter, the obtained molded body was heated at 1100° C. for 2 hours to obtain a temporary sintered body. The heating rate at this time was 120°C/h up to 800°C and 100°C/h up to 1100°C.
  • the pre-sintered body was placed on a 2 mm-thick plate-shaped SiC susceptor, and the 2-mm-thick plate-shaped SiC susceptor was further placed on top of the pre-sintered body, which was housed in a heat insulating container.
  • the heat-insulating container used had the same configuration as the heat-insulating container 20 shown in FIG. 2.
  • the heat insulating container was placed in a microwave heating device. Recrystallized SiC was used for the SiC susceptor.
  • ⁇ -Reactor EX manufactured by Shikoku Keizoku Kogyo Co., Ltd. was used.
  • gas with an oxygen concentration of 90 vol% was supplied into the heat insulating container. Then, while supplying gas, microwave heating was started, and the temperature was increased to 1050°C at a rate of 600°C/min, and up to 1730°C at a rate of 40°C/min, and maintained at 1730°C for 1 minute. Thereafter, the temperature was lowered to 1300°C at a cooling rate of 10°C/min, and when the temperature reached 1300°C, the power to the microwave heating device was turned off to lower the temperature.
  • Example 1 the zirconia sintered body of Example 1 was manufactured. Note that the microwave heating method was multi-mode. Further, for temperature measurement, an OPTCTRF1MHSFVFC3 sensor manufactured by Optris was used to measure the temperature of the SiC susceptor above the pre-sintered body.
  • Example 2 From the manufacturing method of Example 1, the rate of cooling down to 1300°C after microwave heating was changed to 50°C/min. A zirconia sintered body of Example 2 was produced in the same manner as in Example 1 except for the above.
  • Example 3 From the manufacturing method of Example 1, the rate of cooling down to 1300°C after microwave heating was changed to 100°C/min. A zirconia sintered body of Example 3 was produced in the same manner as in Example 1 except for the above.
  • Example 4 From the manufacturing method of Example 1, the rate of cooling down to 1300°C after microwave heating was changed to 200°C/min. A zirconia sintered body of Example 4 was produced in the same manner as in Example 1 except for the above.
  • Example 5 The manufacturing method of Example 1 was changed so that the zirconia powder with an average particle size of 150 nm to 200 nm was not mixed with alumina powder, but instead a polyacrylic binder was mixed at 3% by mass as a binder. This mixture was granulated by spray drying to obtain zirconia granules with an average particle size of 70 ⁇ m. Using such zirconia granules as a material for a molded body, a pre-sintered body was obtained in the same manner as in Example 1, and then heated under the same temperature increasing conditions as in Example 1, and the temperature was lowered to 1300°C at a cooling rate of 100°C/min. Then, when the temperature reached 1300° C., the power to the microwave heating device was turned off, and the zirconia sintered body of Example 5 was manufactured.
  • Example 6 The manufacturing method of Example 5 was changed so that 0.125% by mass of alumina powder was mixed with zirconia powder having an average particle size of 150 nm to 200 nm.
  • the heating rate of microwave heating was 600°C/min up to 1150°C, 20°C/min up to 1200°C, and 40°C/min up to 1620°C, and held at 1620°C for 1 minute. Thereafter, the temperature was lowered to 1300°C at a cooling rate of 50°C/min, and when the temperature reached 1300°C, the power to the microwave heating device was turned off to produce the zirconia sintered body of Example 6.
  • Example 7 The manufacturing method of Example 4 was changed so that the yttria concentration was 5.6 mol%. Further, the proportion of alumina powder was changed to 0.015% by mass. The temperature was raised at a rate of microwave heating of 600°C/min up to 1200°C, 5°C/min up to 1500°C, and 40°C/min up to 1730°C, and held at 1730°C for 1 minute. Thereafter, the temperature was lowered to 1300°C at a cooling rate of 200°C/min, and when the temperature reached 1300°C, the power to the microwave heating device was turned off to produce the zirconia sintered body of Example 7.
  • Example 8 In the manufacturing method of Example 1, heating by microwave was changed to heating by electric furnace. Specifically, the temperature of the temporary sintered body was raised to 1450°C at a rate of 120°C/h, held for 120 minutes, and then lowered at a rate of 5°C/min. The zirconia sintered body of Example 8 was manufactured in the same manner as in Example 1 except for these operations.
  • Example 9 The manufacturing method of Example 8 was changed so that the yttria concentration was 5.6 mol%. Further, the proportion of alumina powder was changed to 0.015% by mass. The zirconia sintered body of Example 9 was manufactured in the same manner as in Example 8 except for these operations.
  • Example 10 Yttrium chloride and ytterbium chloride were mixed into a zirconia sol produced by hydrolyzing a zirconia oxychloride solution.
  • yttrium chloride is converted into yttria
  • ytterbium chloride is converted into ytterbia
  • yttrium chloride and chloride are added so that yttria is 1.7 mol% and ytterbia is 2.4 mol% with respect to the total of zirconia, yttria, and ytterbia.
  • ytterbium After drying the mixture, it was calcined at 1120° C. for 4 hours to obtain partially stabilized zirconia powder.
  • the zirconia powder was pulverized in a ball mill using zirconia balls with a diameter of 1 mm, and then sorted through a mesh sieve to obtain a zirconia powder with an average particle size of 150 nm to 200 nm as a molded body material.
  • Alumina powder having an average particle size of 30 nm was mixed into this powder at a concentration of 0.05% by mass.
  • This zirconia powder was filled into a disk-shaped mold and a pressure of 0.78 MPa was applied, and then the molded body was taken out from the mold and CIP molded at 196 MPa. Thereafter, the obtained molded body was heated at 1100° C. for 2 hours to obtain a temporary sintered body.
  • the heating rate at this time was 120°C/h up to 800°C and 100°C/h up to 1100°C.
  • microwave heating was performed in the same manner as in Example 4, and then the temperature was lowered to 1300° C. at a rate of 200° C./min to obtain a zirconia sintered body of Example 10.
  • the microwave heating conditions were changed to raise the temperature at 600°C/min up to 1050°C, 40°C/min up to 1730°C, and then maintain the temperature at 1730°C for 1 minute.
  • Example 11 In the manufacturing method of Example 10, the microwave heating was changed to heating using an electric furnace. Specifically, the temperature of the temporary sintered body was raised to 1500°C at a rate of 120°C/h, held for 120 minutes, and then lowered at a rate of 5°C/min. This temperature reduction was performed by stopping the heating of the electric furnace and allowing the sintered body to naturally radiate heat within the electric furnace. The zirconia sintered body of Example 11 was manufactured by carrying out the same operations as in Example 10 except for these operations.
  • Example 12 The manufacturing method of Example 10 was changed so that ytterbium chloride was mixed instead of yttrium chloride so that the ytterbium concentration in the zirconia sintered body was 5.6 mol%.
  • the heating rate of microwave heating was 600°C/min up to 1200°C, 5°C/min up to 1500°C, and 40°C/min up to 1730°C, and held at 1730°C for 1 minute. Changed to.
  • a zirconia sintered body of Example 12 was produced in the same manner as in Example 10 except for the above.
  • Example 13 In the manufacturing method of Example 12, the microwave heating was changed to heating using an electric furnace. Specifically, the temperature of the temporary sintered body was raised to 1500°C at a rate of 120°C/h, held for 120 minutes, and then lowered at a rate of 5°C/min. This temperature reduction was performed by stopping the heating of the electric furnace and allowing the sintered body to naturally radiate heat within the electric furnace. The zirconia sintered body of Example 13 was manufactured by carrying out the same operations as in Example 12 except for these operations.
  • Rietveld analysis was performed on the obtained XRD profile using analysis software: RIETAN-FP, and the c/a axis length ratio of the unit cell and the proportion (mass %) of the crystal phase were analyzed.
  • the analysis was conducted using a mixed phase of tetragonal, metastable tetragonal, and cubic crystals, and the temperature parameters of each element were the same.
  • metalastable tetragonal refers to a crystal phase in which only the a-axis length and c-axis length of the tetragonal crystal are different. The results are shown in Table 1.
  • the zirconia sintered body produced in each example was processed into a disk-shaped specimen with a thickness of 1 mm, and diamond slurry (average particle size 0.5 ⁇ m) was used as an abrasive to polish both sides of the specimen. After polishing, the total light transmittance of the D65 light source in the thickness direction was measured. For this measurement, a haze meter NDH4000 manufactured by Nippon Denshoku Industries was used. The results are shown in Table 1.
  • the monoclinic crystal ratio (%) of the zirconia sintered bodies produced in each example was measured according to the method shown below after hydrothermal treatment. Specifically, first, the surface of the zirconia sintered body was mirror-polished with diamond slurry (average particle size: 0.5 ⁇ m). Next, the polished sintered body was subjected to hydrothermal deterioration treatment at 140° C. for 100 hours using a high-pressure microreactor (manufactured by O-M Labotech Co., Ltd.). Thereafter, the X-ray diffraction pattern of the polished surface was measured using an X-ray diffraction device (device name: Ultima IV, manufactured by Rigaku Co., Ltd.).
  • the monoclinic crystal ratio (%) was determined from the following formula.
  • the monoclinic crystal ratio is determined by the X-ray diffraction peak intensity [I m (111)] corresponding to the monoclinic phase (111) plane, and the From the corresponding X-ray diffraction peak intensity [I m (11-1)] and the sum of the X-ray diffraction peak intensities corresponding to the (111) plane of the crystal phase other than the monoclinic phase [I o (111)], It can be calculated.
  • Table 1 The results are shown in Table 1.
  • the crystal phases of the zirconia sintered bodies of Examples 2 to 6 include a crystal phase in which the c/a axis length ratio of the unit cell is within the range of 1.0055 or more and less than 1.010, and a crystal phase in which the c/a axis length ratio of the unit cell is in the range of 1.0055 or more and less than 1.010. 017 or less, and it can be seen that a highly homogeneous crystal phase is realized.
  • Example 8 because the cooling rate was too slow, the crystal phase in which the c/a axis length ratio of the unit cell was within the range of 1.0055 or more and less than 1.010 did not precipitate, and the hydrothermal resistance It is thought that the deterioration property was insufficient. Furthermore, in Example 8, since the zirconia sintered body was produced by heating in an electric furnace, it is thought that the permeability and hydrothermal deterioration resistance are inferior to those sintered by microwave heating.
  • Example 7 has a higher total light transmittance and a lower monoclinic crystallinity after hydrothermal degradation. This is because in Example 7, microwave heating and rapid cooling were performed, and the proportion of the crystal phase in which the c/a axis length ratio of the unit cell was within the range of 1.0055 or more and less than 1.010. This is thought to be due to the fact that it is 100% by mass.
  • Example 10 is an example in which a part of the yttria in Example 4 was replaced with ytterbia, and excellent translucency and excellent hydrothermal deterioration resistance were achieved.
  • the zirconia sintered body has a crystal phase in which the c/a axis length ratio of the unit cell is in the range of 1.0055 or more and less than 1.010, and in the range of more than 1.012 and less than 1.017.
  • the ratio of the crystal phase in which the c/a axis length ratio of the unit cell is within the range of 1.0055 or more and less than 1.010 is 40% by mass or more.
  • Example 11 is an example in which heating was performed using an electric furnace instead of microwave heating, and a crystal phase in which the c/a axis length ratio of the unit cell was within the range of 1.0055 or more and less than 1.010 was measured. It wasn't done. This is thought to be because the entire heating space of the electric furnace was maintained at a high temperature and the rate of temperature drop after sintering was slow, resulting in insufficient hydrothermal deterioration resistance.
  • zirconia sintered bodies having ytterbia instead of yttria were produced. Also in the production of a zirconia sintered body having Ytterbia, microwave heating and rapid cooling produce a crystal phase in which the c/a axis length ratio of the unit cell is within the range of 1.0055 or more and less than 1.010, It can be seen that excellent translucency and excellent hydrothermal deterioration resistance are achieved.
  • ⁇ Test 2> Line analysis by FE-EPMA
  • the zirconia sintered bodies of Examples 2, 4, 7, and 8 were subjected to line analysis using FE-EPMA (manufactured by JEOL Ltd., JXA-8530F) to investigate the intensity distribution of yttrium.
  • the surface of the zirconia sintered body was mirror polished, and line analysis was performed on the surface. The conditions were as follows.
  • ⁇ Detector YWDS detector PETH ⁇ Acceleration voltage: 15kV ⁇ Irradiation current: 5 ⁇ 10 -8 A ⁇ Collection time: 500ms ⁇ Magnification: 50,000 times ⁇ Pixel size: 9.4nm ⁇ Number of measurement points: 256 ⁇ Measurement distance: 2400nm
  • the coefficient of variation of the characteristic X-ray intensity of yttrium was determined.
  • Table 2 shows the coefficient of variation for each example. Note that the measurement region of the line analysis was set to pass through the crystal interface of the zirconia sintered body at least once. Further, graphs of the line analysis results of Examples 2, 4, 7, and 8 are shown in FIGS. 3 to 6, respectively. This graph shows the characteristic X-ray intensity of yttrium on the vertical axis and the measurement distance on the horizontal axis.
  • mapping image of yttrium and a secondary electron image of the same field of view as the mapping image were obtained by STEM-EDX. Images of the zirconia sintered bodies of Examples 4, 7, and 8 are shown in FIGS. 7 to 9, respectively.
  • the left side is a mapping image of yttrium
  • the right side is a secondary electron image. The closer the mapping image is to white, the higher the yttrium intensity, and the closer to black, the lower the yttrium intensity.
  • the coefficient of variation of the characteristic X-ray intensity of yttrium is higher in the zirconia sintered body sintered by microwave heating and rapidly cooled than in the zirconia sintered body sintered in an electric furnace. was low. That is, it can be seen that yttrium is more homogeneously dispersed (concentration unevenness is suppressed) in the zirconia sintered body sintered with microwaves.

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JP2021059489A (ja) * 2019-10-08 2021-04-15 東ソー株式会社 ジルコニア焼結体及びその製造方法
WO2022065452A1 (ja) * 2020-09-25 2022-03-31 クラレノリタケデンタル株式会社 ジルコニア焼結体の製造方法

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JP7578866B1 (ja) * 2023-06-02 2024-11-06 共立マテリアル株式会社 ジルコニア焼結体とその製造方法
WO2024247873A1 (ja) * 2023-06-02 2024-12-05 共立マテリアル株式会社 ジルコニア焼結体とその製造方法
WO2025063305A1 (ja) * 2023-09-22 2025-03-27 クラレノリタケデンタル株式会社 ジルコニア仮焼体及びその製造方法
WO2025063304A1 (ja) * 2023-09-22 2025-03-27 クラレノリタケデンタル株式会社 ジルコニア仮焼体及びその製造方法
JPWO2025063306A1 (https=) * 2023-09-22 2025-03-27
JP7791367B2 (ja) 2023-09-22 2025-12-23 クラレノリタケデンタル株式会社 ジルコニア仮焼体
WO2025206349A1 (ja) * 2024-03-29 2025-10-02 クラレノリタケデンタル株式会社 セラミックス仮焼体の製造方法
JP7820618B1 (ja) * 2024-03-29 2026-02-25 クラレノリタケデンタル株式会社 セラミックス仮焼体の製造方法

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