JP2001139371A - Zirconia sintered compact for optical connector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a zirconia sintered compact for an optical connector having execute durability in a high-temperature atmosphere where moisture exists. SOLUTION: This zirconia sintered compact for the optical connector consisting of ZrO2 as an essential component and containing Y2O3 as a stabilizer is composed mainly of a crystal phase of a tetragonal crystal and is constituted by specifying the solid solution quantity of the Y2O3 in the tetragonal crystal phase to 2.6 to 4 mol%, the average crystal grain size to <=0.5 μm and the ratio of the cubic crystal phase determined by a Rietveld method to 14 to 25 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a zirconia sintered body suitable for optical connector members such as ferrules and sleeves.

[0002]

2. Description of the Related Art In recent years, with an increase in the amount of information in communication, optical communication using optical fibers has been used. In this optical communication, an optical connector is used for connection between optical fibers or connection between an optical fiber and various optical elements.

For example, in the case of a connector for connecting optical fibers, an end of the optical fiber is held in a through hole formed in a ferrule, a pair of ferrules are inserted from both ends of a sleeve, and a convex spherical shape is formed inside. The structure is such that the processed end faces are brought into contact with each other.

Various materials such as ceramics, metals, plastics and glass have been produced as materials for the ferrules and sleeves, but most are now made of ceramics. The reason is that ceramics have high processing accuracy, so that the tolerance of the inner diameter and outer diameter can be as high as 1 μm or less, and ceramics have a low coefficient of friction, so they have excellent optical fiber insertion properties, and have high rigidity and high heat resistance. This is because the low expansion coefficient is stable against external stress and temperature change, and is excellent in corrosion resistance.

Further, in recent years, most ceramics have been replaced with zirconia from alumina. Since this zirconia sintered body has a Young's modulus as low as about half that of alumina, when the tip surfaces of two ferrules come into contact with each other, it is possible to increase the adhesion with a small stress and to have high strength and toughness. Therefore, the reliability can be improved (see Japanese Patent Publication No. 8-30775).

The zirconia sintered body for an optical connector includes ZrO ₂ as a main component and a stabilizer of 2.5 to 2.5%.
About 3.5 mol% (about 4.5 to 6.2 wt%) of Y ₂ O ₃
Is formed and fired to obtain an average grain size of 0.4
A partially stabilized zirconia sintered body mainly composed of a tetragonal crystal phase having a thickness of about 0.6 μm has been proposed (Japanese Patent Laid-Open No. 6-3).
No. 37327).

A raw material containing ZrO ₂ as a main component and Y ₂ O ₃ as a stabilizer and 0.2 to 0.3% by weight of Al ₂ O ₃ added to the raw material is molded and fired. A partially stabilized zirconia for an optical connector mainly composed of the above-mentioned crystal phase has been proposed (see Japanese Patent Application Laid-Open No. 10-260336).

Further, in a zirconia sintered body for an optical connector containing ZrO ₂ as a main component and Y ₂ O ₃ as a stabilizer, the concentration of Y ₂ O ₃ in a tetragonal phase is adjusted to 3.0 mol% or more. Retained partially stabilized zirconia has been proposed (Jour
nal of the Ceramic Society of Japan, September 1999).

[0009]

However, in any of the above-mentioned conventional examples, the partially stabilized zirconia sintered body containing Y ₂ O ₃ cannot be made into a tetragonal crystal when exposed to a high-temperature atmosphere in which water is present. There is a problem in that the crystal of (1) undergoes a phase transformation to monoclinic to deteriorate properties such as strength and toughness.

[0010] Further, the above-mentioned optical connector may be used for a long time in a bad environment depending on the use purpose.
As an accelerated test, a test is performed in which a pair of ferrules are inserted from both ends of the sleeve and the optical connector is exposed to hot water at 85 ° C with the end surfaces processed into a convex spherical shape in contact with each other. There is. At this time, the optical connector member such as a ferrule made of a zirconia sintered body is likely to cause a phenomenon that the connected surface is deformed by the above-described phase transformation and the radius of curvature of the convex spherical surface of the ferrule end surface is increased, As a result, there has been a problem that poor connection or excessive connection loss occurs.

[0011]

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above-mentioned problems, and has been made in view of the above-mentioned problems, and is directed to a zirconia sinter for an optical connector containing ZrO ₂ as a main component and Y ₂ O ₃ as a stabilizer. In the body, the main component is a tetragonal crystal phase, the amount of solid solution of Y ₂ O ₃ in the tetragonal phase is 2.6 to 4 mol%, the average crystal grain size is 0.5 μm or less, and it is determined by Rietveld method The ratio of the cubic phase is 14 to 25% by volume.

That is, as a result of various experiments conducted by the present inventors, a partially stabilized zirconia sintered body containing Y ₂ O ₃ as a stabilizing agent has an average crystal grain size of 0.5 μm or less. It has been found that the durability in high-temperature water is improved by setting the solid solution amount of Y ₂ O ₃ to 2.6 to 4 mol% and the ratio of the cubic phase to 14 to 25 vol%. The reason for this is that the effect of water is reduced by increasing the amount of Y ₂ O ₃ that suppresses the phase transformation to monoclinic in the tetragonal crystal and increasing the proportion of the cubic phase that does not undergo phase transformation. It is considered that the phase transformation at the step was reduced.

[0013]

Embodiments of the present invention will be described below.

As shown in FIG. 1A, a ferrule 1 for an optical connector has a through hole 1 for inserting an optical fiber in the center.
The rear end of the through hole 1a is provided with a conical portion 1b for facilitating insertion of an optical fiber, and the distal end outer periphery is provided with a spherical portion 1c serving as a guide surface when the sleeve is inserted.

As shown in FIG. 1 (b), the sleeve 2 is a cylindrical body, and has a slit 2a in the axial direction to elastically hold the ferrule 1; May not be required. Further, about three convex portions may be formed on the inner peripheral surface, and the ferrule 1 may be supported by these convex portions.

The ferrule 1 is formed of a zirconia sintered body which will be described in detail later. As shown in FIG. 2, the rear side thereof is joined to a metal support 3, and an optical fiber 4 is inserted into the through hole 1a. After joining, the tip surface 1d has a radius of curvature of 1
Polish to a convex spherical shape of about 0 to 25 mm. The optical fibers 4 can be connected to each other by inserting such a pair of ferrules 1 from both ends of the sleeve 2 and pressing them with a spring or the like to bring the tip surfaces 1d into contact with each other.

The zirconia sintered body forming the ferrule 1 and the sleeve 2 contains ZrO ₂ as a main component, contains Y ₂ O ₃ as a stabilizer, and mainly has a tetragonal crystal phase. Has a Y ₂ O ₃ solid solution amount of 2.6 to 4 mol%, an average crystal grain size of 0.5 μm or less, and has a cubic phase ratio of 14 to 25% by volume determined by the Rietveld method. By doing so, it is possible to prevent phase transformation in a high temperature where moisture exists.

Since the zirconia sintered body of the present invention is mainly composed of a tetragonal phase, when subjected to a stress, the tetragonal crystal is transformed into a monoclinic crystal and expands in volume, so that the crack progresses. The mechanism of preventing stress-induced transformation can improve the strength and toughness of the sintered body, and is called partially stabilized zirconia.

Further, the zirconia sintered body of the present invention does not include a monoclinic phase, but also includes a cubic crystal which is stable against phase transformation in addition to a tetragonal phase which is a main component, so that the stress-induced transformation can be prevented. The phase transformation characteristics in high-temperature water can be greatly improved without substantially impairing the mechanism.

Here, the reason why the ratio of the cubic phase determined by the Rietveld method is 14 to 25% by volume is that if it is less than 14% by volume, phase transformation easily occurs in high-temperature water,
On the other hand, if it exceeds 25% by volume, mechanical properties such as bending strength are deteriorated.

The cubic and tetragonal abundances in the zirconia sintered body were determined from the peak heights and area ratios of the tetragonal crystals from the results of X-ray diffraction measurement. Since the peaks overlap, it is very difficult to separate the peaks, so that an accurate crystal ratio cannot be obtained. Therefore, when the characteristics are controlled based on the crystal ratio determined by the conventional method, there is a problem that the characteristics are varied, and even if the crystal ratio is the same in the conventional method, the characteristics are completely different.

On the other hand, in the present invention, the ratio of the cubic phase is determined by X-ray diffraction measurement of the sintered body using CuKα radiation.
is measured in the range of 20 to 80 °, and a mixture of tetragonal and cubic crystals is obtained from this diffraction pattern by the Rietveld method (Fujio Izumi, Journal of the Crystallographic Society of Japan, vol. 27, paragraph 23 (1985)). The difference between the X-ray diffraction pattern calculated by using the ratio, the lattice constant, and the like as parameters and the measured X-ray diffraction pattern of the sample was analyzed and approximated by approximating the least-squares method.

The relationship between the ratio of the cubic phase calculated using the Rietveld method and the phase transformation characteristics in high-temperature water is very excellent, and the ratio of the cubic phase determined by this method is very high. It is very reproducible when controlling the phase transformation characteristics in high-temperature water by using this method, and concluded that the Rietveld method can be used to determine the true crystal phase ratio. By controlling the temperature in the specific range described above, it is possible to stably produce a good crystal having excellent phase transformation characteristics in high-temperature water and little variation.

The reason why the average crystal grain size of the zirconia sintered body of the present invention is set to 0.5 μm or less is that if the average crystal grain size is larger than this, phase transformation is likely to occur, and required characteristics cannot be obtained.

Furthermore, the reason why the Y ₂ O ₃ solid solution amount in tetragonal zirconia is set to 2.6 to 4 mol% is that if it is less than 2.6 mol%, phase transformation occurs in high-temperature water and deformation occurs. However, this is because required characteristics such as an increase in the radius of curvature of the convex spherical surface of the ferrule end surface cannot be obtained. On the other hand, if it exceeds 4 mol%, cubic crystals increase in zirconia, and the proportion of tetragonal crystals that exhibit high strength and high toughness of zirconia due to the stress-induced transformation decreases.

The amount of solid solution of Y ₂ O ₃ in the tetragonal crystal was calculated by the following equation 1 after determining the lattice constants a and c of the tetragonal crystal by the Rietveld method.

[0027]

(Equation 1)

Next, a method of manufacturing the ferrule 1 and the sleeve 2 will be described.

First, ZrO _{2 as} a starting material contains Al ₂ O ₃ , SiO ₂ , TiO ₂ , or CaO, Na as impurities.
_Although it contains ₂ O, Fe ₂ O _3, etc., this raw material is treated with a chemical such as acid or alkali, or purified by a method such as gravity separation utilizing a specific gravity difference to increase the purity. And
The Y ₂ O ₃ was added and mixed 3-5 mol% ZrO _2, was sink neutralizing co is reacted, solid solution by a method such as hydrolysis.

Next, the obtained raw material is formed into a predetermined shape by extrusion molding, press molding, injection molding, or the like, and if necessary, cut and the like, and then fired in the air atmosphere.

At this time, in order to obtain a small average crystal grain size of 0.5 μm or less, it must be fired at a low temperature of 1200 to 1550 ° C. to form a dense sintered body. Can be achieved by making the specific surface area smaller and increasing the specific surface area. Ferrule 1
The sleeve 2 can be obtained by further polishing and grinding this sintered body.

Here, the firing temperature and the average crystal grain size are in a proportional relationship, and the higher the firing temperature, the larger the average crystal grain size. In the zirconia sintered body of the present invention, the average particle size is 0.12 μm at 1200 ° C., 0.23 μm at 1370 °, and 0.5 μm at 1550 °.

In the zirconia sintered body for an optical connector according to the present invention, the average crystal grain size is 0.5 μm or less, and the main component is a tetragonal crystal phase, and the amount of Y ₂ O ₃ solid solution in the tetragonal phase is small. 2.
In order to make 6 to 4 mol% and the ratio of the cubic phase determined by the Rietveld method to 14 to 25 vol%, as described above, ₃ to 5 mol% of Y ₂ O ₃ is added to ZrO ₂ and mixed. It can be achieved by firing at a firing temperature in the range of 1200 to 1550 °, but as the firing temperature is higher and the firing temperature holding time is longer, the proportion of the cubic phase increases, and Y ₂ in the tetragonal crystal is increased. The amount of O ₃ solid solution tends to decrease and the particle size tends to increase.

FIG. 2 shows an optical connector for connecting the optical fibers 4 to each other. However, the ferrule 1 and the sleeve 2 are used for an optical module for connecting an optical element such as a laser diode or a photodiode to the optical fiber. It can also be used.

The zirconia sintered body for an optical connector according to the present invention can be applied to various members used for connecting the optical fibers described above or between the optical fibers and various optical elements. It is not limited to the sleeve 2. For example, the present invention can be applied to a splicer used for completely connecting optical fibers to each other, a dummy ferrule used for an optical module, and the like.

[0036]

Embodiments of the present invention will be described below.

Zirconia raw materials having various compositions were prepared by changing the amount of Y ₂ O ₃ added to ZrO ₂ as a starting material.

Each of the final products has an outer diameter of 2.5 m.
m and a length of 10.5 mm are extruded into the shape of the ferrule shown in FIG.
It was baked at 50 ° C., and ferrule 1 was produced by changing the amount of Y ₂ O ₃ dissolved in tetragonal zirconia and the ratio of the cubic phase as shown in Table 1. The average crystal grain size was measured by a code method using an image taken with a scanning electron microscope.

A ferrule 1 was prepared for each composition, an optical fiber 4 was adhered, and the tip surface 1d was polished so that the radius of curvature of the convex spherical surface was about 15 mm on average. Then, as shown in FIG. 1 was connected in the sleeve 2 and left in hot water at 85 ° C. for 14 days. Then, the amount of change (increase) in the radius of curvature of the tip surface 1d of the ferrule 1 before and after the test was examined using a shape measuring instrument. Table 1 shows the amount of change in the radius of curvature under each condition.

From these results, it was found that Y _{2 in} tetragonal zirconia
O ₃ which amount of solid solution exceeds or 4 mole% less than 2.6 mol%, or / and that the proportion of cubic phase obtained by Rietveld method exceeds or 25% by volume less than 14 vol% (No .1,2,3,4,5,6,7,12,13,18,19,24,25,30,
31, 36), the variation in the radius of curvature is as large as 5.7 mm at least.

On the other hand, the amount of Y ₂ O ₃ dissolved in the tetragonal zirconia of the present invention is 2.6 to 4 mol%, and the ratio of the cubic phase determined by the Rietveld method is 14 to 25 vol%.
(No. 8, 9, 10, 11, 14, 15, 16, 17, 20, 21, 22, 22, 23, 26, 2
7, 28, 29, 32, 33, 34, and 35), the amount of change in the radius of curvature is less than 1 mm, which is a small value that falls within the range of the error in the radius of curvature measurement.

That is, the solid solution amount of Y ₂ O ₃ in tetragonal zirconia is 2.6 to 4 mol%, the average crystal grain size is 0.5 μm or less,
And the ratio of the cubic phase determined by the Rietveld method is 1
By setting the content to 4 to 25% by volume, there was no change in the radius of curvature of the end face of the ferrule even in a test in hot water.

[0043]

[Table 1]

[0044]

As described above, according to the present invention, ZrO ₂
It was the main component, in the optical connector zirconia sintered body containing Y ₂ O ₃ as a stabilizer, mainly the tetragonal phase, Y ₂ O ₃ solid solution amount in the positive direction phase two. By forming the zirconia sintered body for an optical connector with 6 to 4 mol%, an average crystal grain size of 0.5 μm or less, and a cubic phase ratio of 14 to 25% by volume determined by the Rietveld method, the water content is reduced. A zirconia sintered body for optical connectors having excellent durability in an existing high-temperature atmosphere can be obtained.

Further, according to the present invention, by forming the optical connector member from the above-mentioned zirconia sintered body, the amount of change in the radius of curvature of the end face of the ferrule is drastically reduced even in a test in hot water. And can be favorably used for a long period of time.

[Brief description of the drawings]

FIGS. 1A and 1B are views showing a member for an optical connector using a zirconia sintered body of the present invention.

FIG. 2 is a sectional view showing an optical connector using an optical connector member made of a zirconia sintered body of the present invention.

[Explanation of symbols]

 1: Ferrule 2: Sleeve 3: Support 4: Optical fiber

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H036 QA16 QA20 QA45 4G031 AA08 AA12 BA14 BA21 CA01 CA04

Claims (1)

[Claims] 1. ZrO ₂ as a main component and Y ₂ as a stabilizer.
In a zirconia sintered body for an optical connector containing O ₃ , a tetragonal crystal phase is mainly used, and Y ₂ O ₃
2.6-4 mol% solid solution, average crystal grain size 0.5 μm
A zirconia sintered body for an optical connector, wherein the ratio of a cubic phase determined by a Rietveld method is 14 to 25% by volume.