JPH01108162A - Zirconia ceramics - Google Patents

Abstract

PURPOSE:To obtain the titled ceramics having excellent ionic conductivity, bending strength, toughness and heat resistance, by blending Nb or an Nb based substance at a specific ratio in ZrO2. CONSTITUTION:The titled ceramics obtained by blending one or more of Nb or an Nb based substance (e.g. Nb2O5) at 0.3-25% weight ratio and, as necessary, an adequate amount of a stabilizer (Y2O3) in ZrO2 and forming a solid solution by a calcining method under ordinary pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is applicable to daily necessities such as scissors, kitchen knives, and bottle openers, sporting goods such as golf heads (insert materials), and hot plugs (for diesel engines).
secondary combustion chamber).

This relates to zirconia ceramics used for rocker arm chips, etc.

Prior art zirconia (ZrO2) ceramics are similar to other engineering ceramics, silicon nitride (813N).
4) Ceramics and silicon carbide (Ji) Exhibits higher strength and toughness at room temperature than ceramics, so it is used to form daily necessities, sports goods, machine parts, etc. that are used at room temperature.

Zirconia (Zr02) is an ionic crystal consisting of Zr''' and 02-, and has a high melting point of over 2700°C and has many functions such as heat resistance, corrosion resistance, and high strength ionic conductivity. .For this zirconia alone, approximately 2
The crystal structure of the high temperature phase around 200℃ is cubic and %1
The crystal structure of the intermediate temperature phase around 200°C is tetragonal, and 12
The crystal structure of the phase at a temperature lower than around 00°C is monoclinic. For example, when cooling starts from 1500°C, approximately 120°C
At 0°C, when the tetragonal phase in the meso-temperature phase undergoes a phase transition to the monoclinic phase in the low-temperature phase, a volumetric expansion of about 4% by volume occurs.

In this way, zirconia alone becomes a brittle ceramic that is prone to cracking and cracking. For this reason, magnesia (MgO)
, calcia (Cab), yttrium oxide (Y2O
2) etc. are added as a stabilizer. By adding 16 mol% or more in the case of magnesia and calcia, and 7 mol% or more in the case of yttrium oxide, stabilized zirconia is transformed into a cubic crystal that is stable from low to high temperatures. Obtainable. For example, by adding about 3 mol% of ittrim oxide, a stabilizer, which is less than the amount required for complete stabilization, it is possible to create a mixed structure of tetragonal and cubic crystals containing a large amount of tetragonal crystals, and Partially stabilized zirconia is a metastable phase that freezes without a phase transition from tetragonal to cubic.
Ma5tabi11ized Zr02= P S Z)
can be obtained.

Problems to be Solved by the Invention However, although stabilized zirconia, which has a cubic crystal structure, has excellent ionic conductivity, it has poor mechanical properties such as bending strength and toughness, so it cannot be used as a structural ceramic. I couldn't. On the other hand, partially stabilized zirconia has a crystal structure of a metastable tetragonal phase, so it has excellent bending strength and toughness. That is, since the tetragonal grains dispersed in the cubic grains are subjected to compressive stress from the surroundings, the tetragonal grains remain as a metastable phase even at room temperature. Here, if an external stress is applied and the crack grows, and the tip of the crack hits the dispersed tetragonal phase particles, the tetragonal crystal, released from the surrounding compressive stress, undergoes a phase transition to monoclinic crystal and the volume increases. It expands and crushes the tip of the crack, and when the tetragonal grains undergo a phase transition to the monoclinic phase at the tip of the crack, they are dispersed in the direction of crack growth, and the energy of the crack is also dispersed. As a result, cracks grow in a zigzag pattern and have many branches, so the amount of energy required for fracture is enormous, making it difficult to break. Partially stabilized zirconia has excellent mechanical properties such as bending strength and toughness. However, its ionic conductivity is poor.

The present invention solves the problems of the prior art as described above, and aims to provide zirconia ceramics that are excellent in ionic conductivity, mechanical properties such as bending strength and toughness, and heat resistance. .

Means for Solving the Problems In order to achieve the above object, the present invention is made by mixing zirconia with at least 0.3 to 25% by weight of niobium and one or more niobium-based substances. It is something.

action The effects of the above technical means are as follows.

When a part of Zr"0') is replaced by a large ion of Nb"+7), the average cation radius increases and the fluorite structure, that is, the cubic structure, becomes stable in all temperature ranges from low to high temperatures. Furthermore, niobium or a niobium-based substance exists between the zirconia particles, allowing for strong and dense bonding.

In addition, niobium or niobium-based substances themselves have 1400~
It has a heat resistance of 1600℃ and has excellent heat resistance, so
Even when mixed with zirconia, it can exhibit its properties. Furthermore, by using niobium or a niobium-based substance that has electrical conductivity, the action of electrons can be activated.

Example Examples of the present invention will be described below.

In the present invention, as niobium or a niobium-based substance,
Metallic niobium (Wb), niobium carbide (NbC), niobium nitride (NbN), niobium tin (Nb3Sn)
), niobium germanide (Nb3Ge), niobium siliconide (Nb3S+), niobium aluminide (Nb3
Al).

Niobium dioxide (Nb02), Niobium pentoxide (Nb20)
5), lithium niobate (L+Nb03), niobium dichloride (NbC12), niobium trichloride (NM: +3),
Niobium tetrachloride (NM: 14), Niobium pentachloride (NbC
15), Niobium oxychloride (NbOC+3), Niobium difluoride (NbF, ), Niobium trifluoride (NbF3), Niobium tetrafluoride (NbF4), Niobium trifluoride (NbF5)
, niobium oxyfluoride (NbOF3), niobium pentabromide (N
bBrs+), niobium tribromide (NbBr3), niobium tetrabromide (NbBr4), niobium pentabromide (NbBrs), niobium oxybromide (NboBr3), niobium nyodide (N
bF2), niobium triiodide (Nb13), niobium tetraiodide (Nb14), niobium pentaiodide (Nb15)
, niobium oxydide (NbOI3), niobium alkoxide and obethoxide) (Wb(OIL, H5)5)
etc. are used.

Then, niobium and one or more kinds of niobium-based substances are added to zirconia (Zr02) in a weight ratio of at least 0.0.
Zirconia ceramics are produced by mixing 3 to 25%.

Next, the blending ratio and test results of specific examples of the present invention will be explained.

First, an example in which the zirconia ceramic of the present invention was manufactured by a known pressureless sintering method will be described. Zirconia (
Niobium pentoxide (Nb205) was mixed into Zr02) in a range of 0.3 to 25% by weight as shown in Examples 1 to 27 in the table below, and solid solution was formed by an atmospheric pressure sintering method.

According to the above example, by substituting a part of Zr''''' with Nb5+ ions, the average cation radius increases, and the fluorite structure, that is, the cubic structure, is stable at all temperatures from a low temperature range to a high temperature range. Becomes stabilized zirconia that is stable in the range. Moreover, in order to stabilize it, an oxide of a metal with a lower valence than zirconia is dissolved in solid solution, so naturally oxygen is deficient and a large number of oxygen ion vacancies are introduced as shown in the following formula.

(+〒X)ZrO+XNb0 +Zr, xNbx02
゜The zirconia ceramic of the above example was able to improve the ionic conductivity by about 10% compared to the conventional stabilized zirconia. Furthermore, as is clear from the above examples, the zirconia ceramic of the present invention has a bending strength of 160 kgf/m (1570 MPa) at room temperature.
~180 kgf/mrn' (1760 MPa), and had a high melting point of 2900°C or higher, and was found to have excellent bending strength, toughness, and heat resistance.

According to this example, a large number of oxygen ion vacancies are introduced as described above, and it has excellent ionic conductivity, so it is especially suitable for use as an oxygen sensor for automobiles and a solid electrolyte for high-temperature solid electrolyte fuel cells. be.

Next, an example in which the zirconia ceramic of the present invention was produced by a hydrolysis method will be described.

Niobium dichloride (Nb) to zirconyl chloride (ZrOCl2)
C12) from 0.3 to 2 as in Examples 28 to 54 in the table below.
This mixed salt aqueous solution was heated at 100°C.
Boil for 100 hours and hydrolyze as described below.

2+ Z "(OH)2+nH2O→Zro2・(n-2)↓+
2H3o+ Crystalline hydrated zirconia is thus precipitated, and in a similar reaction niobium pentoxide (Nb 205 ) is precipitated and mixed homogeneously into the zirconia. At this time, the solvent (
Itria (Y2O2) is used as a stabilizer to prevent the precipitate from agglomerating. Then, dry the precipitate,
Calcinate to create a powder, crush this powder to create a fine powder, create a green compact from this fine powder, and sinter it to add niobium pentoxide (Nb20) to zirconia (ZrO2).
．． ) was prepared as a solid solution in zirconia ceramics.

In this example as well, as in the case produced by the above-mentioned pressureless sintering method, the cubic crystal structure becomes stabilized zirconia that is stable in the entire temperature range from a low temperature range to a high temperature range, and has excellent ionic conductivity. And the bending strength at room temperature is 160ksrf
/mrn' (1570MPa) ~180kgf/m
m' (17B0 MPa) and has a high melting point of 2900° C. or higher, so it was found that bending strength, toughness, and heat resistance can be improved.

Next, an example in which the zirconia ceramic of the present invention was produced by a coprecipitation method will be described. Zirconyl chloride (Zr
Add niobium dichloride (NbCI2) to OC+) from 0.3 to
It is mixed in an amount of 25% by weight, and an alkali such as N)1408 is added thereto to form a hydroxide sol and co-precipitated to precipitate amorphous hydrated zirconia and niobium pentoxide (Nb205). At this time, itria (Y2O2) is used as a solvent (stabilizer) to prevent the precipitate from agglomerating. Then, the precipitate is dried and calcined to produce a powder, this powder is pulverized to produce a fine powder, a green compact is produced from this fine powder, and zirconia (Z r
Zirconia ceramics were prepared by dissolving niobium pentoxide (Nb205) in O2).

In this example as well, as in the case produced by the above-mentioned hydrolysis method, the cubic crystal structure becomes stabilized zirconia that is stable in the entire temperature range from a low temperature range to a high temperature range, and has excellent ionic conductivity. Furthermore, it was possible to improve bending strength, toughness, and heat resistance.

Note that if the amount of niobium pentoxide mixed with zirconia is 0.
If it is less than 3% by weight, the bending strength, toughness, heat resistance, and ionic conductivity will be poor; if it exceeds 25% by weight, the bending strength, toughness, heat resistance, and ionic conductivity will not improve and the product will be expensive. Become.

In each of the above specific examples, the case where niobium pentoxide was used was explained, but niobium other than niobium pentoxide,
Alternatively, the same effect can be obtained by using one or more niobium-based substances.

Further, the present invention can be manufactured by an alkoxide method in addition to the above-mentioned pressureless sintering method, hydrolysis method, coprecipitation method. In addition to the above-mentioned yttriya (Y2O2), magnesia (MgO), calcia (Cab), cerium oxide (Ce 02 ), etc. can be used as a stabilizer. In addition, since niobium or a niobium-based substance plays the role of the above-mentioned stabilizer or sintering aid, the above-mentioned stabilizer does not have to be used, but even if it is used, it can be used in the conventional manner! /lO
It can be suppressed to about 1/15, and there is no risk of deteriorating the physical properties of zirconia, niobium, or niobium-based materials.

Effects of the Invention In short, according to the present invention, 0.3 to 25% of niobium and one or more of niobium-based substances are added to zirconia.
By making it a solid solution by weight%, a part of Zr becomes Wb”
By replacing the ions with large ions, the average cation radius increases, the cubic crystal structure becomes stable over the entire temperature range from low to high temperatures, and the ionic conductivity can be improved. Also.

Since niobium or niobium-based substances exist between zirconia particles and can be strongly and densely bonded,
Bending strength and toughness can be improved. Furthermore, since niobium or a niobium-based substance itself has excellent heat resistance, heat resistance can be improved. therefore,
In addition to the above-mentioned applications, it can be used in an extremely wide range of applications as described below, which could not be used with conventional stabilized zirconia or partially stabilized zirconia.

(1) Oxygen sensor for automobiles (2) Solid electrolyte for high-temperature solid electrolyte fuel cells (3) Cutlery for general users, industrial use, hairdressing, scissors for magnetic tape, table knife, kitchen knife, fruit knife, chestnut leather Cutters for peeling machines, horizontal cutting machines, paper processing machines, metal thin plate cutting machines, electric clippers, planers, and noodle making machines.

(4) Ball for crusher (5) Sports and daily necessities Golf clubs, fishing gear, spiked shoes.

watch bearing.

(6) Mechanical parts Printer wire guides, guide rollers for VTRs, pump parts, various bearings, wire guides for wire-cut electric discharge machines, bearing rollers for robot rotary tables, rotary bearings for stirrers, valve seats for silk machines , thread guide, and parts for wire drawing machines.

(7) Other bin sets, drivers for electrical work, adjusters, dies, nozzles, punches, and springs.

Claims (1)

[Claims] A zirconia ceramic characterized by being formed by mixing at least 0.3 to 25% by weight of niobium and one or more niobium-based substances into zirconia.