Luminous glass ceramics

Details Luminous glass ceramics Luminous glass ceramics

1998-12-03

2001-03-06

Group, Karl (Department: 1755)

Compositions: ceramic

Ceramic compositions

Devitrified glass-ceramics

C501S007000, C501S063000, C501S064000, C252S30160P, C252S30140R, C252S30140P, C065S033100, C065S033800

Reexamination Certificate

active

06197710

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to luminous glass ceramics containing rare earth elements in a glass phase and/or a crystallized phase, wherein thermal conductivity, a character of thermal expansion, mechanical strength, of the luminous glass ceramics are improved and further having various emission wavelengths. In particular, the invention relates to luminous glass ceramics which can be suitably applied to an oscillation medium for laser oscillation, an excitation light filter or the like.
2. Description of Related Art
For materials which are used as the luminous materials in earlier technology, a glass material, a single crystal material, and a ceramic material have been known.
However, there are problems of the thermal conductivity and the thermal expansion in the glass material. That is, because the glass material has low thermal conductivity and a high coefficient of thermal expansion, when the glass material is subjected to irradiation by an excitation light with high intensity, there is a problem that the glass material breaks under thermal expansion thereof because occurred heat is hard to escape therefrom. When the glass material is used under such environmental circumstances, temperature of which is largely or rapidly changed, there is a problem that the glass material breaks under thermal fatigue thereof.
For example, the luminous glass material which is applied to the oscillation medium for laser oscillation or the wavelength conversion filter for excitation light of laser breaks under the thermal stress because the thermal conductivity of the glass material is low and the temperature distribution thereof becomes non-uniform when the glass material is subjected to irradiation by the laser.
On the other hand, there are problems for the single crystal material that it is difficult to uniformly dope the optically active element to the single crystal material and to produce a practically large size of product of the single crystal material. There is a problem that the ceramic material is liable to occur a light scattering caused by grain boundaries and pores, of the ceramic material, which is character thereof.
SUMMARY OF THE INVENTION
The present invention has been developed in view of the problems.
An object of the present invention is to provide luminous glass ceramics having the superior thermal properties, for example, being hard to break under the locally thermal expansion thereof or a heat shock, or the like, caused by the low thermal conductivity and by the high coefficient of thermal expansion, whereby the problems of the luminous materials in earlier technology can be solved.
Another object of the invention is to provide luminous glass ceramics which can solve the problems in the non-uniform distribution of the optically active element in the single crystal material in earlier technology and in the occurrence of the light scattering caused by the grain boundaries and the pores, of the ceramic material in the earlier technology.
Further object of the invention is to provide luminous glass ceramics which have formability which is similar to the glass and can be easily produced.
Still further object of the invention is to provide a method for producing luminous glass ceramics having the superior thermal properties above-described.
The inventors have made various efforts to solve the problems above-described. As the result, it is developed that the glass ceramics having a rare earth element in glass phase and/or crystallized phase, the main crystallized phase of which is &bgr;-quartz, &bgr;-quartz solid solution, spinel crystal, or solid solution of spinel crystal has superior thermal character, a little occurrence of the light scattering, formability which is similar to the glass so that it can be easily produced. Then, the inventors have achieved the invention.
In order to accomplish the above objects, in accordance with one aspect of the invention, a luminous glass ceramic having a thermal shock resistance |&Dgr;t|° C. of not less than 150° C., wherein the thermal shock resistance |&Dgr;t| is obtained by following equation, |&Dgr;t|[flexural strength]×(1−[Poisson's ratio])/([coefficient of thermal expansion]×[Young's modulus]). The luminous glass ceramic can have thermal conductivity of not less than 1.1 W/(m·K) and comprise: a main crystallized phase selected from a group consisting of &bgr;-quartz and &bgr;-quartz solid solution; and a rare earth element contained in one selected from a group consisting of a glass phase, a crystallized phase, and both of the glass and crystallized phases, of the glass ceramic.
The &bgr;-quartz solid solution has another component which substitutes for a part of the &bgr;-quartz crystal and/or invades the &bgr;-quartz crystal. The &bgr;-quartz solid solution includes &bgr;-eucryptite, i.e., &bgr;-Li
2
O.Al
2
O
3
.2SiO
2
, wherein Li and Al are substitutes for Si in &bgr;-quartz crystal in a ratio of 1:1, and &bgr;-eucryptite solid solution wherein another component further substitutes for a part of the &bgr;-eucryptite and/or invades the &bgr;-eucryptite.
In the luminous glass ceramic, a grain size of a deposited crystal therein can be not more than 900 Å; a coefficient of thermal expansion thereof can be −10×10
−7
to +20×10
−7
/° C. in a temperature range of −60° C. to +160° C.; and a maximal variation of &Dgr;L/L curve, which is a variation in relative length can be not more than 2×10
−5
in a temperature range of −60° C. to +160° C. The luminous glass ceramic can comprise the following components:
Wt. %
SiO
2
50-65
P
2
O
5
 0-10
Al
2
O
3
18-30
Li
2
O
2-6
MgO
0.2-6  
ZnO
0-2
CaO
0-4
BaO
0.5-6  
TiO
2
1-4
ZrO
2
1-4
As
2
O
3
+ Sb
2
O
3
0-2
wherein a total amount of SiO
2
and P
2
O
5
can be 50-70 wt. %, a ratio of P
2
O
5
to SiO
2
can be 0-0.18, a ratio of Al
2
O
3
to SiO
2
can be 0.30-0.55, one or more rare earth elements can be added to the glass ceramic on an oxide basis of 0.1-30 wt. % to an total amount of other components, and Na
2
O component, K
2
O component, and PbO component can not be essentially contained.
The luminous glass ceramic can be produced by a method comprising the steps of: melting a mixture of raw materials of the components; forming the melted mixture and annealing the formed mixture; subjecting the annealed product to a nucleating temperature of 650-820° C.; and subjecting the resulting product to a crystallizing temperature of 750-920° C.
The luminous glass ceramic can comprise: a main crystallized phase selected from a group consisting of a, spinel crystal and solid solution of spinel crystal; and a rare earth element contained in one selected from a group consisting of a glass phase, a crystallized phase, and both of the glass and crystallized phases, of the glass ceramic.
In the application, the spinel crystal shows one or more types selected from a group consisting of (Mg and/or Zn)Al
2
O
4
, (Mg and/or Zn)
2
TiO
4
, and a mixture of solid solution between these two crystals.
The solid solution between two crystals shows one which consists only of the element contained in (Mg and/or Zn)Al
2
O
4
and (Mg and/or Zn)
2
TiO
4
, wherein the element substitutes for a part of the two crystals and/or invades the two crystal.
The solid solution of spinel crystal has another component which substitutes for a part of the spinel crystal and/or invades the spinel crystal.
In the luminous glass ceramic a grain size of a deposited crystal therein can be not more than 300 Å; and a coefficient of thermal expansion thereof can be 25×10
−7
to 85×10
−7
/° C. in a temperature range of −60° C. to +160° C. The luminous glass ceramic can comprise the following components:
Wt. %
SiO
2
30-65 
Al
2
O
3
5-35
MgO
1-20
BaO
0.3-4  
ZnO
5-35
TiO
2
1-15
As
2
O
3
+ Sb
2
O
3
0-3 
wher

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