JPH07187708A - Fluoride glass - Google Patents

Abstract

PURPOSE:To obtain fluoride glass being transparent in a wide wavelength range from the ultraviolet range to the infrared range, having more excellent chemical permanence and mechanical strength than those of ZBLAN-based glass and stability to crystallization. CONSTITUTION:This fluoride glass comprises 2-28mol% ZnF2, 5-22mol% AlF3 5-40mol% ZrF4 or HfF4 or the total of both 12-45 mol % SrF2 or BaF2 or the total of both, 0-15mol% CaF2, 0-10mol% MgF2 0-15mol% PbF2 and 0.5-30mol% YbF3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluoride glass which can be used as an infrared ray transmitting fiber for optical communication and medical use, laser glass, up-conversion laser glass, optical glass, etc. The present invention relates to a fluoride glass having higher mechanical durability and mechanical strength than the ZBLAN type.

[0002]

2. Description of the Related Art Fluoride glass such as ZrF ₄ system is transparent over a wide wavelength range from ultraviolet to infrared, and particularly 2 to
The theoretical optical transmission loss in the 4 μm band is as small as 0.01 dB / km, and is expected as a fiber for next-generation optical communication. It can also be used for various lenses, prisms, filters used in the infrared region, fibers for laser power transmission for optical measurement, and the like. Since the phonon energy is smaller than that of oxide glass, it is a promising material for optical amplification and up-conversion laser host material in the 1.3 μm band.

Since the discovery of ZrF ₄ type fluoride glass in 1974, research and development on fluoride glass have been actively conducted, and ZBLAN (JP-A-57-166335), ZBGA (JP-A-SHO).
58-49644), YABC (JP-A-57-123843), IGTBY (JP-A-62-171944), and many new types of fluoride glass have been developed. However, fluoride glass has a drawback that it is much more easily crystallized than ordinary oxide glass. What is considered to be a fluoride glass that is currently in practical use is the ZBLAN system (JP-A-57-166335).
Gazette) and AlF ₃ -ZrF ₄ -CaF ₂ system (JP-A-62-275039) and InF ₃ -ZnF ₂ system (Proceedings of the 8th International Halide Glass Symposium, p380 (1992)). Among them ZBLA
N-based glass is the most stable glass against crystallization. However, since ZBLAN-based glass contains a large amount of NaF introduced to improve the stability against crystallization,
Its chemical durability is quite poor, its mechanical strength is low, and it has the major drawbacks that when it is normally used in the atmosphere, it reacts with water and is prone to deterioration and damage. On the other hand, AlF ₃ -ZrF ₄ -CaF ₂ type glass has stronger mechanical strength and better chemical durability than ZBLAN type glass, so it is thought that it can be used for various optical devices, but it is thermally It is unstable and has the drawback of being easier to crystallize than ZBLAN glass. Although this glass exhibits the above-mentioned good chemical durability and mechanical strength, it is more thermally unstable than ZBLAN glass,
It is still difficult to prepare a uniform and large sample and to make it into a fiber.

[0004]

Therefore, the present invention solves the above-mentioned drawbacks of conventional glass, is transparent over a wide wavelength range from ultraviolet to infrared, and has chemical durability and mechanical strength superior to that of ZBLAN glass. An object of the present invention is to provide a fluoride glass which is excellent and stable against crystallization.

[0005]

[Means for Solving the Problems] In order to increase the stability of the fluoride glass against crystallization, the Tm
Based on the idea that it is necessary to lower (liquidus temperature of glass) and raise Tx (temperature at which glass begins to crystallize), as a result of intensive research, ZnF ₂ -AlF ₃ -ZrF ₄ (HfF ₄ ) -S
In the rF ₂ (BaF ₂ ) -LnF ₃ (Ln = Yb, La, Gd, Y) system, Tx is the crystallization start temperature of the glass, Tg is the glass transition temperature, and ΔT (= Tx−Tg) is large. Wide allowable temperature range for fiber drawing, small critical cooling rate, and
We obtained a fluoride glass that has better chemical durability than ZBLAN glass. The larger the ΔT (= Tx−Tg), the higher the stability against crystallization.

That is, the fluoride glass of the present invention is expressed in mol% as ZnF ₂ is ₂ to 28%, AlF ₃ is 5 to 22%, and ZrF ₄ is
5-40% of either or both of HfF ₄ and SrF ₂
12 to 45% of Ca or BaF ₂ or both in total, Ca
F ₂ 0 to 15%, MgF ₂ 0 to 10%, PbF ₂ 0 to 15%, YbF ₃
The first feature is to contain 0.5 to 30%.
Further, the fluoride glass of the present invention has a ZnF ₂ content expressed in mol%.
10-25%, AlF ₃ 10-18%, ZrF ₄ and / or HfF ₄ 10-25% in total, SrF ₂ and BaF _{2 1} or both in total 15-30 %, CaF ₂ 0-10%, Mg
The second feature is that it contains 0 to 8% of F ₂ , 0 to 10% of PbF ₂ , and 5 to 25% of YbF ₃ . Further, the fluoride glass of the present invention, in mol% display, ZnF ₂ is ₂ to 28%, AlF ₃ is 5 to 22%, either or both of ZrF ₄ and HfF ₄ are 5 to 40% in total, Either or both of SrF ₂ and BaF ₂ are 12-45% in total, CaF ₂ is 0-15%, MgF ₂ is 0-10%, PbF ₂
The third characteristic is to contain 0 to 15% of YbF ₃ , LaF ₃ , GdF ₃ and YF _{3 in} a total amount of 0.5 to 30%. Further, the fluoride glass of the present invention, in mol% display, ZnF ₂ is 10 to 25%, AlF ₃ is 10 to 18%, one or both of ZrF ₄ and HfF ₄ is 10 to 25% in total, Either or both of SrF ₂ and BaF ₂ are 15 to 30% in total, and CaF ₂ is 0 to 0%.
10%, MgF ₂ 0-8%, PbF ₂ 0-10%, YbF ₃ and LaF ₃
The fourth characteristic is that a total of 5 to 25% of one or more of GdF ₃ and YF ₃ is contained.

In the above characteristics, among the rare earth fluorides, YbF ₃ is more preferable than the other rare earth fluorides because it is more effective in increasing the stability against crystallization and is most preferable. This is Yb
^{It is considered that the 3+} ion is heavier than other rare earth ions and has a small ionic radius, so that the bond with F is strong, and thus it is difficult for the transition in the glass network structure. CaF ₂ , Mg
F ₂ and PbF ₂ are used for adjusting the refractive index of glass. The more PbF _2, the higher the refractive index. CaF ₂ and MgF ₂ raise or lower the refractive index depending on the partner with which they are replaced. If the composition of the present fluoride glass is outside the range shown in the first characteristic or outside the range shown in the third characteristic, the glass tends to crystallize, and a uniform and large glass cannot be obtained. Further, in consideration of fiber moldability, stability against crystallization, chemical durability, mechanical strength, etc., the range is preferably the range shown in the second characteristic or the fourth characteristic. Within the composition range shown in the first to fourth features of the present invention, colorless and transparent glass having a thickness of 6 mm or more can be obtained by a conventional casting cooling method. In addition, the melt is poured into a mold heated near the glass transition temperature (Tg),
It is possible to make a transparent glass rod of φ10 × 80 mm.

[0008]

Example 30 kinds of glass samples having compositions within the composition ranges shown in the first and third characteristics of the present invention were prepared. High-purity fluoride raw material was weighed in a glove box replaced with argon gas, and about 10 wt% of NH ₄ HF ₂ was added and mixed so that 30 g of glass was finally obtained for each sample. Platinum, gold, alloys of gold and platinum,
Or put it in a glassy carbon crucible and place it in an Ar atmosphere at 80
After melting at 0-1100 ℃ for about 45 minutes, pour into a brass mold,
A colorless and transparent glass having a thickness of 6 mm or more was obtained. Tables 1-3
The measurement results of the glass composition and physical properties of each sample are shown.

[0009]

[Table 1]

[0010]

[Table 2]

[0011]

[Table 3]

The stability of the glass against crystallization was evaluated using DTA. The obtained glass transition temperature (Tg) and crystallization temperature (Tx), and ΔT (= Tx-Tg) are also shown in the table. Figure 1 shows an example of DTA curve of this glass (Sample 23)
The difference between Tx (glass crystallization onset temperature) and Tg (glass transition temperature) obtained from this figure is 142 ° C.
82 ° C of system (H. Tokiwa et., Al, J. Lightwave Technol.
Lt-3, 574-578 (1985)) and AlF ₃ -ZrF ₄ -CaF ₂ system 107 ℃
(Fluoride Glasses, Edited by Alan E. Comyns, p41
(1989), John Wiley & Sons). Fig. 2 shows 25ZnF ₂・ 15AlF ₃・ 23ZrF ₄・ 12 when the kind of rare earth is changed.
SrF ₂・ 15BaF ₂・ 10LnF ₃ (Ln = La, Y, Gd, Yb) glass
The DTA curve is shown. From this figure, when the type of Ln is changed, the transition temperature (Tg) of the glass hardly changes, but ΔT (=
Tx-Tg) is Ln = La (Sample 30), Y (Sample 26), Gd (Sample)
29), Yb (Sample 1), 137 ℃, 142 ℃,
It becomes 156 ℃ and 160 ℃, increasing in this order. That is, it was found that Yb was the most effective in improving the stability of the glass against crystallization. This is related to the ionic radius, the ease of transition of Ln ³⁺ ions in the glass network structure, etc. Further, as can be seen from Tables 1 to 3, in the composition within the composition range of the present invention, ΔT (= Tx−Tg) is 80 to
Glass at 160 ° C was easily obtained. It can be seen that the glass of the present invention has good stability against crystallization. Further, the critical cooling rate was determined for the examples of the glass of the present invention. The critical cooling rate obtained for sample 1 is 30 ℃ / min, which is 40-70 ℃ / min for ZBGA system, 55 ℃ / min for ZBLA system and HBLA.
Was lower than 60-180 ° C / min and higher than 3 ° C / min of ZBLAN system, but was about the same as 25 ° C / min of ZBLALi system (criticality of glasses other than the glass of the present invention). The cooling rate was quoted from M. Poulain, J. Non-cryst. Solids, 1-9 (1992) 140). Since the glass of the present invention has a low critical cooling rate, a stable amorphous glass can be obtained without being crystallized at the time of forming a glass rod. That is, it can be seen that it has good glass forming characteristics.

On the other hand, the chemical durability of ZBLAN-based or ZBLALi-based glass is poor because a large amount of ZrF ₄ and NaF or LiF is used.
It is believed that this is due to the inclusion of Sample 1 and ZBLAN-based glass (composition mol%: 51 for ZrF ₄ and BaF ₂
20, LaF ₃ is 4.5, AlF ₃ is 4.5, NaF is 20), a φ10 × 80 mm rod is made by the same method, annealed, and then cut and polished into a sample with a thickness of 9 mm,
After immersion in 100 ml of ion-exchanged water, the water resistance was evaluated by infrared spectrum. As a result, when the ZBLAN glass was immersed in water for 4 hours, the absorption peak intensity around 3500 cm ^-1 due to the OH group formed by the reaction of the glass and H ₂ O, the sample 1 sample was immersed in water for 24 hours. However, it was larger than the absorption peak intensity. Also, when the surface was observed with a microscope, ZBLAN
When the system glass was immersed in water for 10 minutes, the surface became rough and crystals were generated on the surface by the hydration reaction. On the other hand, the glass of Sample 1 did not show any change in the surface condition even after being immersed in water for 24 hours. It is considered that this is because the glass of the present invention contains no alkali at all and the content of ZrF ₄ is sufficiently reduced, and therefore the chemical durability is superior to that of ZBLAN. When Vickers hardness was measured (measurement condition: load 5 kg, load time 15 seconds), ZBLAN system had 227 kg / cm ²
On the other hand, the glass of Sample 1 has 292 kg / cm ² ,
It can be seen that the glass of the present invention containing no alkali metal fluoride has higher mechanical strength than the ZBLAN system.

[0014]

EFFECTS OF THE INVENTION The present invention has the above-mentioned constitution, and according to the fluoride glass described in the claims, ZrF ₄ which does not contain alkali metal ions and therefore contains a large amount of NaF or LiF is used as a main component. Compared with ZBLAN (Li) -based fluoride glass, it has superior mechanical strength and chemical durability, and is sufficiently stable against crystallization. Therefore, it is very promising as a new infrared transmitting material, and its application to optical communication, medical, measurement fiber, etc. can be expected.

[Brief description of drawings]

FIG. 1 is a diagram showing an example (Sample 23) of a DTA curve of a fluoride glass of the present invention.

[Fig.2] 25ZnF ₂・ 15AlF ₃・ 23ZrF ₄・ 12SrF ₂・ 15BaF ₂・ 10
LnF ₃ (Ln = Yb (Sample 1), Ln = Gd (Sample 29), Ln = Y
(Sample 26), Ln = La (Sample 30)) DTA curve of the glass.

Claims (4)

[Claims] 1. In terms of mol%, ZnF ₂ is ₂ to 28%, AlF ₃ is 5 to 22%, and either or both of ZrF ₄ and HfF ₄ are 5 to 40% in total.
%, SrF ₂ and / or BaF _{2 12} to 45 in total
%, CaF ₂ 0 to 15%, MgF ₂ 0 to 10%, PbF ₂ 0 to 15%, YbF ₃ 0.5 to 30%, a fluoride glass. 2. ZnF ₂ is 10 to 25%, AlF ₃ is 10 to 18%, and one or both of ZrF ₄ and HfF ₄ is 10 to 25 in total in mol%.
%, SrF ₂ and / or BaF ₂ 15 to 30 in total
%, CaF ₂ 0 to 10%, MgF ₂ 0 to 8%, PbF ₂ 0 to 10%, YbF ₃ 5 to 25%, and a fluoride glass. 3. ZnF ₂ is ₂ to 28%, AlF ₃ is 5 to 22%, and one or both of ZrF ₄ and HfF ₄ is 5 to 40 in total in mol%.
%, SrF ₂ and / or BaF _{2 12} to 45 in total
%, CaF ₂ 0 to 15%, MgF ₂ 0 to 10%, PbF ₂ 0 to 15%, YbF ₃ , LaF ₃ , GdF ₃ and YF ₃ any one or more in total.
Fluoride glass characterized by containing 5 to 30%. 4. ZnF ₂ is 10 to 25%, AlF ₃ is 10 to 18%, and one or both of ZrF ₄ and HfF ₄ in total is 10 to 25 in mol%.
%, SrF ₂ and / or BaF ₂ 15 to 30 in total
%, CaF ₂ 0-10%, MgF ₂ 0-8%, PbF ₂ 0-10%, YbF ₃ , LaF ₃ , GdF ₃ and YF ₃ one or more in total 5
Fluoride glass characterized by containing ~ 25%.