JP6238286B2 - Zirconia continuous fiber and production method thereof - Google Patents

Description

The present invention relates to a zirconia continuous fiber, and more particularly to a zirconia continuous fiber suitable for use as a reinforcing fiber of continuous fiber reinforced ceramics.
Moreover, this invention relates to the manufacturing method of the partially stabilized zirconia continuous fiber or stabilized zirconia continuous fiber used for a zirconia continuous fiber.

  Zirconia is monoclinic at room temperature, and the crystal structure undergoes phase transition to tetragonal and cubic crystals as the temperature is raised. Since this phase transition is accompanied by a volume change, the sintered body is broken by repeatedly raising and lowering the temperature. In particular, in the phase transition from monoclinic to tetragonal, a volume shrinkage of about 4% is observed.

  When a rare earth oxide such as calcium oxide, magnesium oxide, or yttrium oxide is dissolved in zirconia, oxygen vacancies are formed in the structure, and the cubic and tetragonal crystals are stable or metastable at room temperature. Destruction can be suppressed. Zirconia to which an oxide called a stabilizer is added is called stabilized zirconia or partially stabilized zirconia.

Stabilized zirconia is superior in mechanical properties such as strength and toughness compared to oxide-free zirconia. This is because the propagation of cracks, which cause fracture, is hindered by the phase transformation from tetragonal to monoclinic and the stress concentration at the crack tip is relaxed. This unique mechanism is called “stress-induced phase transformation strengthening mechanism”, and at most about 40% of tetragonal crystals are transformed into monoclinic crystals. Further, it is known that partially stabilized zirconia in which the amount of the additive is reduced to allow slight transformation is superior to the fully stabilized zirconia in which the transformation is completely suppressed.
Furthermore, ceramic fibers are useful materials used in various fields such as electrical insulating materials, heat insulating materials, fillers, and filters, taking advantage of properties such as electrical insulation, low thermal conductivity, and high elasticity. It is the same.

Zirconia fibers can be produced by various methods. For example, they can be produced by using an aqueous solution of a zirconium salt as a starting material, which is then baked at a high temperature.
Specifically, an inorganic salt method in which a water-soluble organic polymer such as polyethylene oxide or polyvinyl alcohol is added to a zirconium salt aqueous solution to form a viscous liquid, which is blown from a nozzle and fired (Patent Document 1), ZrO _2. A slurry method in which ZrOCl ₂ is added to a fine powder and crystal stabilizer as a binder to form a viscous slurry, which is dry-spun and fired (Patent Document 2), an organic acid salt of zirconium is melted and spun and fired (Non-Patent Document 1) and the like. Conventionally, it is well known that fibers can be formed by a sol-gel method using a metal alkoxide as a raw material.

Thus, although it is possible to make zirconia into a fibrous form, since these fibers are polycrystalline, deterioration due to grain growth is likely to occur at a high temperature, and characteristics such as mechanical strength are monocrystalline. There is a problem that it is inferior to fiber.
Therefore, many methods for producing single crystal fibers of ceramic materials have been proposed. With regard to zirconia, single crystal fibers can be made by a hydrothermal synthesis method, a laser heating method, or a vapor phase method. Further, an electrospinning method is known as a method for producing a fiber thinner than a conventional fiber and increasing its strength. The electrospinning method is a method in which a high voltage is applied to a fiber-forming solution, the solution is ejected toward the electrode, the solvent is evaporated by the ejection, and an ultrafine fiber structure can be easily obtained. A zirconia fiber having an average fiber diameter of 50 to 1000 nm and a fiber length of 100 μm or more is obtained (Patent Document 3).

However, these are extremely short fibers, and there is a problem that they cannot be used as reinforcing fibers for continuous fiber reinforced ceramics.
Conventional zirconia continuous fibers, in particular, stabilized zirconia, could be melted, that is, melted into a stretched fiber, but its melting point is as high as 2700 ° C., so the production cost is very high. There was a problem. Moreover, in the manufacturing method of the stabilized zirconia fiber by the above-mentioned inorganic salt method or the sol-gel method, since the fiber obtained is a polycrystal, it is easy to cause deterioration due to grain growth at high temperature, and mechanical strength and the like There was a problem that it was not enough.

Japanese Patent Publication No.55-36726 Japanese Unexamined Patent Publication No. 60-246817 JP 2006-336121 A

J. Am. Ceram. Soc. , 70 (1987) C187

Since conventional zirconia fibers are polycrystalline, they are prone to degradation due to grain growth at high temperatures, and there are problems in handling properties due to low properties such as mechanical strength. As a fiber for long fiber reinforced composite materials, Could not be used.
Therefore, an object of the present invention is to provide a stabilized zirconia continuous fiber or a partially stabilized zirconia continuous fiber that can be used for a zirconia fiber reinforced zirconia composite material and a method for producing the same, which solve the above-mentioned problems. is there.

  As a result of intensive studies on a method for producing continuous zirconia fibers, which uses alkoxide as a raw material, has very few impurities such as alkali, and can impart an amorphous structure by controlling the amount of carbon contained therein. The present invention has been reached. That is, the present invention is as follows.

  The method for producing a continuous zirconium oxide fiber according to the present invention enables partial spinning by performing partial hydrolytic condensation of zirconium alkoxide in the presence of partially stabilized zirconia or a metal alkoxide that forms an oxide component that forms stabilized zirconia. A first step of forming a precursor, a second step of continuous spinning at a high speed by melting or dry spinning, a third step of infusibility in a controlled steam atmosphere, and low-temperature firing in an oxidizing atmosphere. A fourth step of converting to a gel fiber containing a carbon component and a fifth step of firing in a non-oxidizing atmosphere and converting to a zirconia fiber containing carbon are provided.

The method for producing a continuous zirconium oxide fiber of the present invention preferably has a sixth step of accelerating crystallization by ultra-high temperature rise.
In the method for producing a continuous zirconium oxide fiber of the present invention, preferably, in the first step, the partially stabilized zirconia or the oxide component forming the stabilized zirconia is yttria (Y ₂ O ₃ ), ceria (Ce ₂ O _3). ) Or Elvia (Er ₂ O ₃ ).

  In the method for producing a continuous zirconium oxide fiber of the present invention, preferably, in the third step, the infusibility of the precursor fiber is set to be within 24 hours in the atmosphere at room temperature or from room temperature to 30 ° C. It is good to carry out by hold | maintaining in 0.5 to 2 hours in the saturated water vapor atmosphere.

In the method for producing a continuous zirconium oxide fiber of the present invention, preferably, the infusible precursor fiber in the fourth step is heated at 10 to 100 ° C./hour in an oxidizing atmosphere in the air or in dry air. It is good to heat to 150-500 degreeC by speed | rate, hold | maintain for 10 hours or less, low-temperature baking, and to convert into the gel fiber containing a carbon component.
In the method for producing a zirconium oxide continuous fiber of the present invention, preferably, in the fifth step, the gel fiber obtained in the fourth step is heated in a non-oxidizing atmosphere such as nitrogen gas or argon gas at a heating rate of 500 to 1000. It is good to calcinate at 800 ° C. or more at ° C./hour and convert to zirconia fiber containing about 1 to 6% by mass of carbon.

  In the method for producing a continuous zirconium oxide fiber of the present invention, preferably, in the sixth step, the gel fiber obtained in the fifth step is 1000 to 1600 at a temperature rising rate of 800 to 20000 ° C./hour in the air. It is preferable to heat up to ° C., promote crystallization while oxidizing and removing carbon, and advance sintering to obtain a stabilized zirconia fiber or a partially stabilized zirconia fiber.

The zirconium oxide continuous fiber of this invention says the zirconium oxide continuous fiber which contains about 1-6 mass% of carbon obtained at the 5th process of the said manufacturing method.
Moreover, the zirconium oxide continuous fiber containing about 1 to 6% by mass of carbon of the present invention is a stabilized zirconium oxide continuous fiber or a partially stabilized zirconium oxide continuous fiber having a carbon content of 1% by mass or less in the sixth step. Can be converted to

In the present invention, partially stabilized zirconia continuous fibers or stabilized zirconia continuous fibers can be obtained.
Further, according to the present invention, by adding a small amount of carbon in the zirconia continuous fiber, the fiber porosity due to crystallization can be suppressed, and a fiber having excellent mechanical strength can be obtained. Further, by adding the sixth step to the present invention, a dense highly crystallized zirconia fiber having a lower carbon content can be obtained by a firing step at a higher temperature by rapid temperature increase.

It is a SEM photograph of 3YSZ fiber obtained by baking at 1000 ° C at 800 ° C / hour in nitrogen gas. This is an XRD of 3YSZ fiber obtained by firing at 1000 ° C. in nitrogen gas at 800 ° C./hour. It is a SEM photograph of the section of 3YSZ fiber obtained by baking at 1000 ° C. at 800 ° C./hour in nitrogen gas. It is a SEM photograph of 3YSZ fiber obtained by baking at 1500 degreeC at 1666 degreeC / hour in air | atmosphere. It is a SEM photograph of the section of 3YSZ fiber obtained by firing at 1500 ° C. at 1666 ° C./hour in the air. It is an XRD of 3YSZ fiber obtained by firing at 1500 ° C. at 1666 ° C./hour in the air. It is XRD of 6YSZ fiber obtained by baking at 1500 degreeC at 1666 degreeC / hour in air | atmosphere. It is an XRD of 8YSZ fiber obtained by firing at 1500 ° C. at 1666 ° C./hour in the air. It is a SEM photograph of the section of Elvia 6 mol% stabilized zirconia fiber obtained by firing at 1400 ° C. in the atmosphere at 15000 ° C./hour.

The present invention will be specifically described below.
The manufacturing method of the zirconia fiber of this invention is as follows.
In the first step of the zirconia fiber production method of the present invention, a partial hydrolysis condensation of zirconium alkoxide is performed in the presence of a metal alkoxide to synthesize a precursor capable of continuous spinning. Here, this metal alkoxide generates partially stabilized zirconia or an oxide component that forms stabilized zirconia. When zirconium alkoxide is used as the metal alkoxide, for example, zirconium tetra-n-butoxide Zr (OC ₄ H ₉ ) ₄ is preferable, but zirconium tetra-i-propoxide, zirconium tetra-sec-butoxide, zirconium tetra- It may be t-butoxide.
The stabilizer may include a compound that serves as a stabilizer, that is, a rare earth element such as yttrium, cerium, or erbium, or a compound such as an alkaline earth metal such as calcium or magnesium, but is uniformly mixed with the zirconium alkoxide. For this purpose, an alkoxide is preferable, and yttrium tetraisopropoxide is preferable. An alkoxide is dissolved in isopropanol and a predetermined amount is mixed with zirconium alkoxide. Preferably the amount of mixing is 2 to 12 mol% in terms of oxide stabilizer against ZrO _2, is less than 2 mol% poor effect, oxide is more than 12 mol% is It is not preferable because the properties of the fiber deteriorate due to precipitation.

In order to partially hydrolyze the mixture of zirconium alkoxide and the above stabilizer, chelation is performed with β-diketon. As β-diketon, ethyl 3-oxobutanoate is preferred. The amount of ethyl 3-oxobutanoate used is preferably 0.1 to 2 moles of the metal alkoxide.
In order to hydrolyze zirconium tetra-n-butoxide, a mixed solution of water, hydrochloric acid and isopropanol is added and stirred. Although each usage-amount is not specifically limited with respect to a metal alkoxide, Isopropanol may be about 3 times mole. Water is preferably 0.3 to 2 moles, and hydrochloric acid is preferably 0.1 to 0.5 moles as HCl. When the amount of water relative to the alkoxide is 0.3 times mol or less, the reaction does not proceed sufficiently and the molecular weight is not increased. If it is 2 moles or more, high molecular weight is excessively advanced, and spinning becomes difficult or gelation occurs, which is not preferable.
Mixing of the stabilizer may be after this reaction.

Next, concentration is performed while proceeding hydrolysis under reduced pressure while gradually raising the temperature from room temperature to obtain a spinnable precursor. The concentration temperature may be up to approximately 90 ° C.
In the second step of the present invention, the precursor obtained in the first step is continuously spun at a high speed by a melt spinning method. The spinning temperature is preferably about 90 ° C. If the spinning temperature is high, the reaction proceeds in the spinning cylinder, and foaming, gelation, etc. may occur. The precursor obtained in the first step can be dissolved once again in a solvent such as isopropanol, and a precursor solution having an appropriate viscosity can be similarly dry-spun.

  In the third step of the present invention, the obtained precursor fiber is infusibilized in a controlled water vapor atmosphere. The purpose of infusibilization is to prevent hydrolysis and condensation of alkoxy groups or chelate moieties remaining in the precursor to cross-link between the molecules to melt and fuse the fibers in the third step. However, if this infusibilization is advanced too much, the fiber becomes brittle and in some cases powders, so the degree of hydrolysis condensation is controlled. The holding time in the air is within 24 hours, and in a saturated water vapor atmosphere, it is preferably 0.5 hours or more and 2 hours or less at 30 ° C. Further steam treatment is not preferred for the above reasons.

  In the fourth step of the present invention, the infusible fiber obtained in the third step is fired at a low temperature in an oxidizing atmosphere to convert it into a gel fiber containing a carbon component. The oxidizing atmosphere may be in the air, but may be dry air. The purpose is to appropriately remove organic substances such as solvents and alkoxy groups remaining in the infusible fiber, and to produce zirconia fiber having strength by firing in the fifth step. Therefore, when infusibilization is completely performed in the third step, dry air or a non-oxidizing atmosphere such as dry nitrogen gas may be used. The temperature for low-temperature firing is preferably around 150 to 500 ° C., more preferably 200 to 300 ° C., around the temperature at which the solvent is removed and the alkoxy groups and chelates are decomposed and removed. The holding time is preferably within 10 hours so that the organic matter does not decrease too much. If the rate of temperature increase is too high, bubbles are likely to be generated in the fiber or a non-uniform structure is likely to be generated, so 10 to 100 ° C./hour is preferable.

  In the fifth step of the present invention, the gel fiber is baked in a non-oxidizing atmosphere and converted to carbon-containing zirconia fiber. The non-oxidizing atmosphere may be an inert gas such as nitrogen gas or argon gas, but argon gas is used when a nitriding reaction of the stabilizer occurs to produce nitride. By this firing, a stabilized zirconia fiber or a partially stabilized zirconia fiber characterized in that carbon remains in the fiber and has low crystallinity (referred to as amorphous) is obtained. The calcination temperature is preferably 800 ° C. or higher, and if it is lower than 800 ° C., the organic carbon component is large (hydrocarbon remains), which is not preferable. The heating rate is preferably 500 to 1000 ° C./hour. Below 500 ° C./hour, the crystallization of zirconia progresses and the fiber strength decreases due to the formation of pores in the fiber, which is considered to be caused by separation from the carbon component. Degradation of organic matter is too rapid and fiber strength is reduced.

  In the sixth step of the present invention, crystallization can be further promoted by an ultra-high temperature rise if necessary. Since the fiber obtained in the fifth step contains carbon, if it is better to have a low carbon content according to the application, the temperature is increased from 1000 to 1600 ° C. at a heating rate of 800 to 20000 ° C./hour in the atmosphere. Sintering is advanced while heating and removing carbon by oxidation, and sinterable stabilized zirconia fibers or partially stabilized zirconia fibers having a low carbon content can be obtained. If the rate of temperature rise is less than 800 ° C./hour, crystallization proceeds excessively, resulting in a fiber having developed pores. The oxidizing firing atmosphere may be oxygen or dry air.

By the above production method, a dense stabilized zirconia fiber or partially stabilized zirconia fiber having low crystallinity can be obtained. The reason is estimated as follows, but the reason is not necessarily limited to this estimation.
Unlike the conventional zirconia fiber, the fiber obtained by the 5th process of this invention contains about 1-6 mass% carbon as shown in an Example. As is apparent from the results of powder X-ray diffraction of the fiber obtained by firing at 1000 ° C., the half-width of the diffraction line is large, indicating that it is amorphous. Therefore, the residual carbon suppresses zirconia crystallization, and as a result, the fiber shows a cross section without pores in which crystal grains are not grown, as can be seen from the SEM photograph. In addition, even when firing at a higher temperature in an oxidizing atmosphere to promote crystallization, firing is performed at an ultra-high temperature while suppressing crystallization by the carbon component, thus minimizing void formation and promoting densification. Estimated.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
<Example 1>
First, in the first step, an equimolar amount of ethyl 3-oxobutanoate was mixed with a predetermined amount of zirconium tetra-n-butoxide, and after the exothermic reaction was completed, 1.2 times the molar amount of H _{2 of} zirconium tetra-n-butoxide. O and hydrochloric acid were made into a solution using 2-propanol and mixed with the zirconia precursor. At this time, hydrochloric acid was used as HCl to make 0.3 mol of zirconium tetra-n-butoxide. After the exothermic reaction, the calculated amount of yttrium tri-2-propoxide in 2-propanol was mixed with the zirconia precursor solution so that Y ₂ O ₃ was 3, 6 or 8 mol% with respect to ZrO ₂ . The mixture was stirred for 15 minutes. Then, using a rotary evaporator, the reaction proceeds while gradually heating from room temperature in a water bath to remove low-boiling components such as solvent and 2-propanol, a hydrolysis product, and concentrate to 85 ° C to stabilize yttria. A zirconia fiber precursor was obtained.

In the next second step, the precursor obtained in the first step is put into a spinning cylinder, the spinning cylinder is heated, the precursor is heated to about 85 ° C., and the inside of the spinning cylinder is pressurized to about 2 MPa with nitrogen gas. The precursor was continuously wound at a speed of about 100 m / min while extruding the precursor from a nozzle having a diameter of 180 μm.
In the next third step, the obtained raw fiber was infusibilized by being kept in saturated steam at 30 ° C. for 1 hour or in the atmosphere at room temperature for 12 hours or 24 hours. Infusibilization was confirmed by not melting on a hot plate at 150 ° C.

In the next fourth step, the infusible fiber was heated to 200 ° C. or 300 ° C. at 50 ° C./hour in the air, and held at 200 ° C. for 5 hours or 300 ° C. for 1 hour to obtain a gel fiber. All fibers are colored from yellow to brown, and it can be confirmed that carbon derived from organic components is contained. Gel fibers containing 3 mol% of yttria contain 15.2% by mass of carbon as a result of carbon analysis. Was.
In the next fifth step, these gel fibers were baked in nitrogen gas at a heating rate of 800 ° C./hour and held at 1000 ° C. for 1 hour to convert them into zirconia fibers containing carbon. The fiber diameter was approximately 10-50 μm (FIG. 1).

  Table 1 shows examples of infusibilization conditions, carbon content and mechanical properties of the zirconia continuous fibers obtained in this example (yttria is referred to as xYSZ fiber, where x is the number of moles of yttria). As can be seen from the result of X-ray diffraction of the 3YSZ fiber in FIG. 2, zirconia fibers having low crystallinity were obtained by this firing.

  FIG. 3 shows an SEM photograph of a cross section of 3YSZ fiber. Formation of zirconia grains in the fiber was not observed.

<Example 2>
In Example 1, 3YSZ, 6YSZ, and 8YSZ fibers obtained by insolubilization in the atmosphere and gelling at 200 ° C. and then firing at 1000 ° C. were heated to 1500 ° C. at 1666 ° C. · h ⁻¹ in the atmosphere. Holding for 5 minutes, 3YSZ, 6YSZ, and 8YSZ fibers were obtained. The carbon contents of these fibers were 0.07, 0.02, and 0.03% by mass, respectively, and it was found that they were almost disappeared by firing in the atmosphere. However, as shown in FIGS. 4 and 5, it was found that the fiber diameter was approximately 10 to 50 μm and the cross section was relatively dense.
From the XRD of these fibers, it was found that 3YSZ fibers were a mixed system of cubic and tetragonal crystals, and 6YSZ fibers and 8YSZ fibers were almost cubic and stabilized (FIGS. 6, 7, and 8). .

<Example 3>
Ceria-stabilized zirconia fiber precursor in the same manner as in Example 1 except that cerium tri-2-propoxide is mixed in an amount of 12 mol% with respect to ZrO ₂ instead of yttrium tri-2-propoxide. Got. This precursor was pressurized to about 2.5 MPa with nitrogen gas at 90 ° C. and continuously wound at a speed of about 80 m / min while being extruded from a nozzle having a diameter of 180 μm.
The obtained raw fiber was kept in the atmosphere at room temperature for 15 hours to be infusible.
The infusible fiber was heated to 200 ° C. at 50 ° C./hour in the air and held at 200 ° C. for 5 hours to obtain a gel fiber.

  This gel fiber was fired in nitrogen gas at a heating rate of 800 ° C./hour, held at 800 ° C. for 1 hour, converted to zirconia fiber containing carbon, and further fired to 1500 ° C. at 1000 ° C./hour. Hold for 1 hour. The fiber diameter was approximately 30 μm and the carbon content was 1.2% by mass. This fiber was found to be almost cubic from the XRD measurement results. The cross section showed a dense structure with almost no voids.

<Example 4>
Mixing erbium tri-2-propoxide instead of yttrium tri-2-propoxide to ₆ , 8, 12 mol% with respect to ZrO ₂ , and adding them to zirconium tetra-n-butoxide in 50% A precursor of erbia (erbium oxide) stabilized zirconia fiber was obtained in the same manner as in Example 1 except that it was added after partial hydrolysis to ° C. This precursor was pressurized to about 2.2 MPa with nitrogen gas at 87 ° C. and continuously wound at a speed of about 80 to 150 m / min while being extruded from a nozzle having a diameter of 180 μm.
The obtained raw fiber was kept in the atmosphere at room temperature for 12 hours to be infusible.

The infusible fiber was heated up to 200 ° C. at 40 ° C./hour in the air and held at 200 ° C. for 1 hour to obtain a gel fiber.
This gel fiber was baked in nitrogen gas at a heating rate of 750 ° C./hour and held at 1000 ° C. for 1 hour to obtain a zirconia fiber containing carbon. The crystal structure of the fibers stabilized with Elvia 6, 8, and 12 mol% was amorphous stabilized zirconia fibers, and the fiber diameter was approximately 18 to 30 μm. All the fibers had tensile strengths and Young's modulus in the range of 0.8 to 1.5 GPa and 150 to 190 GPa. The carbon content was 2.9% by mass with 6% by mass erbia-stabilized zirconia fiber.
Further, the 8 mass% erbia-stabilized zirconia fiber was fired in Ar gas at 10000 ° C./hour to 1400 ° C. and held for 5 minutes to obtain a stabilized zirconia fiber containing 1.0 mass% carbon. The fiber diameter was approximately 20 μm, and the results of XRD revealed that the fiber was almost cubic. The carbon content was 1.2% by mass.

Moreover, the 6 mass% elvia-stabilized zirconia fiber was fired in the atmosphere at 15000 ° C./hour to 1400 ° C. and held for 5 minutes to obtain a stabilized zirconia fiber containing 0.3 mass% of carbon. The fiber diameter was approximately 15 μm, and the results of XRD revealed that the fiber was almost cubic.
As shown in FIG. 9, the cross section of the fiber showed a dense structure with crystal growth and almost no voids.

According to the production method of the present invention, by containing a small amount of carbon in the zirconia continuous fiber, the porosity of the fiber due to crystallization can be suppressed, and a fiber having excellent mechanical strength can be obtained. Further, if necessary, a dense highly crystallized zirconia fiber having a low carbon content by firing at a higher temperature by subsequent rapid temperature increase can be obtained. Therefore, these zirconia continuous fibers are suitable for use in the production of a zirconia fiber reinforced oxide ceramic composite material having an oxide as a matrix.

Claims (7)

A first step of performing a partial hydrolytic condensation of zirconium alkoxide in the presence of partially stabilized zirconia or a metal alkoxide that forms an oxide component forming stabilized zirconia to form a precursor capable of continuous spinning;
A second step of continuously spinning this at a high speed by a melt or dry spinning method;
A third step infusible in a controlled water vapor atmosphere;
A fourth step of low-temperature firing in an oxidizing atmosphere to convert to a gel fiber containing a carbon component;
A fifth step of firing in a non-oxidizing atmosphere and converting to carbon-containing zirconia fibers;
The manufacturing method of a zirconium oxide continuous fiber provided with this.   Furthermore, the manufacturing method of the zirconium oxide continuous fiber of Claim 1 which has a 6th process of promoting crystallization by ultra high-speed temperature rising.   3. The partially stabilized zirconia or the oxide component that forms the stabilized zirconia in the first step is yttria (Y 2 O 3), ceria (Ce 2 O 3), or erbia (Er 2 O 3). A method for producing a continuous zirconium oxide fiber.   In the third step, the infusibilization of the precursor fiber is maintained at room temperature in the atmosphere for 24 hours or in a saturated steam atmosphere at room temperature to 30 ° C. for 0.5 hours to 2 hours. The method for producing a continuous zirconium oxide fiber according to any one of claims 1 to 3, wherein the method is performed.   In the fourth step, the infusible precursor fiber is heated to 150 to 500 ° C. at a temperature rising rate of 10 to 100 ° C./hour in an oxidizing atmosphere in the air or in dry air and held for 10 hours or less. The method for producing a continuous zirconium oxide fiber according to any one of claims 1 to 4, wherein the method is converted to a gel fiber containing a carbon component by firing at a low temperature.   In the fifth step, the gel fiber obtained in the fourth step is baked at 800 ° C. or higher at a temperature rising rate of 500 to 1000 ° C./hour in a non-oxidizing atmosphere such as nitrogen gas or argon gas. The method for producing a continuous zirconium oxide fiber according to any one of claims 1 to 5, wherein the continuous zirconia fiber is contained in an amount of about 6% by mass. In the sixth step, the zirconium oxide continuous fiber obtained in the fifth step is heated to 1000 to 1600 ° C. at a temperature rising rate of 800 to 20000 ° C./hour in the air to crystallize while removing carbon by oxidation. The method for producing a continuous zirconium oxide fiber according to any one of claims 2 to 6, wherein the stabilized zirconia fiber or the partially stabilized zirconia fiber is obtained by promoting the sintering.