JPH0253371B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a novel cadrinium scandium aluminum garnet crystal useful as a luminescent material and a method for producing the same. [Prior Art] Cadolinium scandium aluminum garnet crystals with luminescent properties include crystals to which chromium is added (for example, those made by Optics Communications).
50, 45 (1984)) is known. [Problems to be Solved by the Invention and Objects of the Invention] The conventional chromium-added materials have a narrow emission region (approximately 650 to 990 nm) and have the problem that absorption from an excited state occurs in the emission region. An object of the present invention is to provide a cadrinium scandium aluminum garnet crystal useful as a luminescent material that has a wider luminescent range and less absorption from an excited state than conventional crystals, and a method for producing the same. [Summary of the Invention] As a result of intensive research to achieve the above object, the present inventors have found that when titanium is added in place of chromium in the conventional chromium-doped gadolinium scandium aluminum garnet crystal, the emission region becomes wider and the excitation It was discovered that the crystal has luminescent properties with little absorption from the state, and the present invention was completed based on this knowledge. The gist of the present invention is the general formula (Gd _1-x Sc _x ) ₃ {Ti _u (Gd _y Sc _z Al _1-
yz ) _1-u } ₂ Al ₃ O ₁₂ (However, x, y, z, and u are each 0≦x≦
0.1, 0≦y≦0.1, 0.1≦z≦1.0, 0.002≦u≦0.2
titanium-added gadolinium scandium aluminum garnet crystals expressed by (indicating numerical values in the range of
= {3(1-x)+2y(1-u)}: {3x+2z(1-
u)}:{2(1-y-z)(1-u)+3}: Mix thoroughly at a quantitative ratio of 2u, and the resulting mixture is melted and solidified in an inert gas or reducing gas atmosphere. 1. A method for producing titanium-doped gadolinium scandium aluminum garnet crystals, characterized in that the crystals are obtained by The amount of titanium added to the crystals of the present invention is in the range of 0.002 to 0.2 as shown by the general formula u. If the amount is less than 0.002, it will not emit light, and if it is more than 0.2, it will not form a solid solution. In addition, x, y, z in the above general formula are 0≦x≦0.1, 0≦y
The range is ≦0.1, 0.1≦z≦1.0. Within this range, a garnet single phase can be obtained, but outside this range, a second phase such as a perovskite phase is generated and a single crystal cannot be obtained, so it is necessary that the content be within these ranges. The garnet crystal of the present invention contains gadolinium oxide (Gd ₂ O ₃ ), scandium oxide (Sc ₂ O ₃ ), aluminum oxide (Al ₂ O ₃ ), and titanium oxide (TiO, _{Ti2O3 ,}
TiO ₂ , Ti ₃ O ₅ or a mixture thereof (preferably using Ti ₂ O ₃ );
It can be obtained by melting and solidifying a mixture of these in an inert or reducing gas atmosphere using a floating zone method or a Czyochralski method. At this time, a mixed gas containing nitrogen, argon, or helium and hydrogen in an amount of 5 vol% or less, preferably 0.05 vol% to 2.0 vol% is used as the atmospheric gas. The reason for this is that garnet does not become a single phase when melted and solidified in an oxidizing atmosphere.
A second phase that is thought to be Gd ₂ Ti ₂ O ₇ precipitates, and if only inert gas is used, it becomes a single phase, but the amount of solid solution of trivalent titanium is small and a non-containing phase containing more than 5.0 vol% hydrogen is formed. This is because, in the case of active gas, many color centers are generated in the obtained crystal, which deteriorates the quality as a luminescent material. The preferred hydrogen content range is 0.05~
It is 2.0vol%. In this way, a garnet crystal in which trivalent titanium is stably dissolved in solid solution is obtained. The titanium-doped crystal of the present invention has a light emitting region of approximately 670nm to 1050nm.
m, and since the active ion has a simple electronic structure with one d electron, absorption from the excited state is small. Example 1 Oxides of gadolinium, scandium, aluminum and titanium were prepared as Gd:Sc:Al:Ti (atomic ratio)
The mixture adjusted to = 2.95: 1.84: 3.19: 0.02 was placed in an iridium crucible and the rotation speed of the seed crystal was adjusted under a nitrogen gas atmosphere containing 2 vol% hydrogen.
Crystals were grown by the Czyochralski method at 15 rpm and a pulling speed of 1 mm/h. As a result, diameter 15
A crystal with a length of 55 mm was obtained. The X-ray diffraction pattern of the obtained crystal is shown in FIG. The crystal obtained from the results of X-ray diffraction has a garnet single phase, and the lattice constant is a.
= 12.378 Å. In addition, as a result of elemental analysis,
The composition of the crystal was Gd _3.019 Ti _0.006 Sc _1.901 Al _3.074 O ₁₂ . The absorption spectrum of the obtained crystal is shown in FIG. The absorption spectrum is characterized by 540nm.
A shoulder and a broad peak corresponding to the electronic transition from the T ₂₉ state to the E ₉ state are seen around 640 nm. Figure 3 shows the emission spectrum when excited with a krypton laser (647 nm). Approximately 670n when excited with krypton laser
It emitted light in the region of m to 1050 nm. Example 2 Oxides of gadolinium, scandium, aluminum and titanium were prepared as Gd:Sc:Al:Ti (atomic ratio)
Using a mixture adjusted to have a ratio of =2.92:1.83:3.15:0.1 as a raw material, crystals were grown by the Czyochralski method in a nitrogen atmosphere containing 1 vol% hydrogen at the same rotation speed and pulling speed as in Example 1. . The composition of the obtained crystal is Gd _3.025 Ti _0.014 Sc _1.837 Al _3.124 O ₁₂
It was hot. The X-ray diffraction pattern and absorption spectrum of the obtained crystal are shown in FIGS. 1 and 2 together with Example 1. The obtained crystal had a single phase, and the patterns of absorption and emission spectra were similar to those shown in Example 1. [Effects of the Invention] The present invention provides a titanium-doped gadolinium scandium aluminum garnet crystal, which is a new crystal useful as a near-infrared luminescent material.

[Brief explanation of drawings]

Figure 1 shows the X of the crystals obtained in Examples 1 and 2.
The line diffraction diagram, FIG. 2 shows the absorption spectrum of the crystal obtained in Examples 1 and 2, and FIG. 3 shows the emission spectrum of the crystal obtained in Example 1.

Claims (1)

[Claims] 1 General formula (Gd _1-x Sc _x ) ₃ {Ti _u (Gd _y Sc _z Al _1-
yz ) _1-u } ₂ Al ₃ O ₁₂ (However, x, y, z, and u are each 0≦x≦
0.1, 0≦y≦0.1, 0.1≦z≦1.0, 0.002≦u≦0.2
) titanium-doped gadolinium scandium aluminum garnet crystal. 2 Gadolinium, scandium, aluminum, and titanium oxides as Gd:Sc:Al:Ti (atomic ratio) = {3(1-x)+2y(1-u)}:{3x+2z(1
−
u)}:{2(1-y-z)(1-u)+3}: Mix thoroughly at a quantitative ratio of 2u, and the resulting mixture is melted and solidified in an inert gas or reducing gas atmosphere. A method for producing titanium-added cadrinium scandium aluminum garnet crystals, characterized by obtaining crystals. 3 As titanium oxides, TiO, Ti ₂ O ₃ ,
3. The method according to claim 2, wherein TiO ₂ , Ti ₃ O ₅ or a mixture thereof is used. 4. The method according to claim 2 or 3, wherein an inert gas containing 5 vol% or less hydrogen is used as the reducing gas.