JP2019094253A - Glass material - Google Patents

Abstract

To provide a glass material having high quantum yield and suitable for phosphors and scintillators.SOLUTION: A glass material contains, in mol%, POof 40-80%, LiO of more than 0 to 50%, AlOof more than 0 to 15%, CeO+EuO+PrO+TbOof more than 0 to 10%.SELECTED DRAWING: None

Description

  The present invention relates to a glass material suitable for a fluorescent substance which is excited by light, heat and radiation to emit fluorescence and a scintillator which is excited by radiation such as neutron beam to emit fluorescence.

  A scintillator is a substance that emits fluorescence by being excited by radiation such as γ-rays or neutrons, and is used in combination with a photodetector such as a photomultiplier tube for PET (positron emission tomography) inspection, nondestructive inspection, It can be used for logging and the like.

  The scintillator is required to have a high quantum yield (the ratio of the number of photons of light emitted by light emission to the number of photons of light absorbed).

Examples of the scintillator include inorganic crystals such as NaI: Tl and Bi ₄ Ge ₃ O ₁₂ , and glass materials containing rare earth elements (see Patent Documents 1 and 2). Glass materials are easier to homogenize and larger than inorganic crystals, and are excellent in processability.

Patent No. 4352149 JP, 2005-75916, A

  However, the scintillator made of the conventional glass material has a problem that the quantum yield is lower than that of the scintillator made of inorganic crystal.

  In view of the above, it is an object of the present invention to provide a glass material which has a high quantum yield and is suitable for a phosphor or a scintillator.

The glass material of the present invention is, in mole%, P ₂ O ₅ 40-80%, Li ₂ O 0 over 50%, Al ₂ O ₃ 0 over 15%, Ce ₂ O ₃ + EuO + Pr ₂ O ₃ + Tb ₂ O ₃₀ characterized by containing more than 0 to 10%. Here, “Ce ₂ O ₃ + EuO + Pr ₂ O ₃ + Tb ₂ O ₃ ” means the total content of the Ce ₂ O ₃ , EuO, Pr ₂ O ₃ and Tb ₂ O ₃ contents.

It is preferable that the glass material of the present invention further contains MgO + CaO + SrO + BaO + ZnO 0 to 10%, B ₂ O ₃ 0 to 5%, SnO 0 to 5%, and F ₂ 0 to 30% in mol%. Here, “MgO + CaO + SrO + BaO + ZnO” means the total content of MgO, CaO, SrO, BaO and ZnO.

In the glass material of the present invention, the ratio of ⁶ Li to total Li is preferably 95% or more in mol%.

  The glass material of the present invention is preferably used as a phosphor.

  The glass material of the present invention is preferably used as a scintillator.

  According to the present invention, it is possible to provide a glass material which has a high quantum yield and is suitable for a phosphor or a scintillator.

The glass material of the present invention is, in mole%, P ₂ O ₅ 40-80%, Li ₂ O 0 over 50%, Al ₂ O ₃ 0 over 15%, Ce ₂ O ₃ + EuO + Pr ₂ O ₃ + Tb ₂ O ₃ 0 containing ultra 10%. The reasons for limiting the glass composition as described above are as follows. In the following description regarding the content of each component, “%” means “mol%” unless otherwise noted.

P ₂ O ₅ is a component that forms a glass network. The content of P ₂ O ₅ is 40 to 80%, preferably 50 to 70%, particularly 55 to 65%. When the content of P ₂ O ₅ is too small, the glass becomes thermally unstable, and the glass tends to be devitrified at the time of melting or firing. On the other hand, when the content of P ₂ O ₅ is too large, chemical durability tends to be reduced.

Li ₂ O is a component that lowers the viscosity of the glass at the time of melting and facilitates obtaining a homogeneous glass. Moreover, when using as a scintillator which detects neutrons, it is essential as a component which captures neutrons. The content of Li ₂ O is more than 0 to 50%, preferably 5 to 45%, 10 to 40%, 15 to 35%, particularly 16 to 34%. When the content of Li ₂ O is too small, the viscosity of the glass at the time of melting becomes high, and it becomes difficult to obtain a homogeneous glass. Moreover, it becomes difficult to use as a scintillator for detecting neutrons. On the other hand, when the content of Li ₂ O is too large, the glass becomes thermally unstable, and the glass tends to be devitrified at the time of melting, and the chemical durability tends to be reduced.

There are two isotopes of ⁶ Li and ⁷ Li in Li, but ⁶ Li can capture neutrons more efficiently than ⁷ Li. Therefore, the larger the proportion of ⁶ Li in the glass material, the easier it is to detect neutrons. Specifically, the ratio of ⁶ Li to total Li is preferably 95% or more, 96% or more, and particularly preferably 97% or more in mol%.

Al ₂ O ₃ is a component that enhances chemical durability and quantum yield. The content of Al ₂ O ₃ is more than 0 to 15%, preferably ₃ to 14%, particularly 5 to 12%. If the content of Al ₂ O ₃ is too low, the chemical durability and the quantum yield tend to be reduced. On the other hand, when the content of Al ₂ O ₃ is too large, the glass becomes thermally unstable, and the glass tends to be devitrified at the time of melting or firing.

Ce ₂ O ₃ , EuO, Pr ₂ O ₃ and Tb ₂ O ₃ are components for emitting fluorescence by being excited by light, heat, radiation and the like. The content of Ce ₂ O ₃ + EuO + Pr ₂ O ₃ + Tb ₂ O ₃ is more than 0 to 10%, preferably 0.1 to 7%, 0.5 to 5%, particularly preferably 1 to 2.5%. . When the content of Ce ₂ O ₃ + EuO + Pr ₂ O ₃ + Tb ₂ O ₃ is too small, it becomes difficult to emit fluorescence. On the other hand, if the content of Ce ₂ O ₃ + EuO + Pr ₂ O ₃ + Tb ₂ O ₃ is too large, the quantum yield is likely to be reduced due to concentration quenching. In addition, although Ce, Pr, and Tb in glass exist in a trivalent or tetravalent state, all of these are represented as Ce ₂ O ₃ , Pr ₂ O ₃ , and Tb ₂ O _{3 in} the present invention. Further, Eu in glass exists in a divalent or trivalent state, but in the present invention, all of these are represented as EuO.

The preferable content of each component of Ce ₂ O ₃ , EuO, Pr ₂ O ₃ and Tb ₂ O ₃ is as follows.

Among Ce ₂ O ₃ , EuO, Pr ₂ O ₃ and Tb ₂ O ₃ , Ce ₂ O ₃ is a particularly effective component for emitting fluorescence. The content of Ce ₂ O ₃ is preferably more than 0 to 10%, 0.1 to 7%, 0.5 to 5%, particularly 1 to 2.5%. When the content of Ce ₂ O ₃ is too low, it becomes difficult to emit fluorescence. On the other hand, when the content of Ce ₂ O ₃ is too large, the quantum yield is likely to decrease due to concentration quenching.

In addition, since Ce emits fluorescence in a trivalent state, the ratio of Ce ^{3+ in} all Ce is 70% or more, 80% or more, 90% or more, 95% or more, and particularly 99% or more in mol%. Is preferred.

  EuO is a component for emitting fluorescence. The content of EuO is preferably 0 to 10%, 0 to 7%, 0 to 5%, 0.1 to 2.5%, particularly 0.1 to 2%. When the content of EuO is too large, concentration quenching tends to lower the quantum yield.

  Eu emits fluorescence in both divalent and trivalent states.

Pr ₂ O ₃ is a component for emitting fluorescence. The content of Pr ₂ O ₃ is preferably 0 to 10%, 0 to 7%, 0 to 5%, 0.1 to 2.5%, particularly 0.1 to 2%. When the content of Pr ₂ O ₃ is too large, concentration quenching tends to lower the quantum yield.

In addition, since Pr emits fluorescence in a trivalent state, the ratio of Pr ^{3+ in} total Pr is 50% or more, 60% or more, 70% or more, 80% or more, particularly 90% or more in mol% Is preferred.

Tb ₂ O ₃ is a component for emitting fluorescence. The content of Tb ₂ O ₃ is preferably 0 to 10%, 0 to 7%, 0 to 5%, 0.1 to 2.5%, particularly 0.1 to 2%. When the content of Tb ₂ O ₃ is too large, concentration quenching tends to lower the quantum yield.

In addition, since Tb emits fluorescence in a trivalent state, the proportion of Tb ^{3+ in} all Tb is 50% or more, 60% or more, 70% or more, 80% or more, and particularly 90% or more in mol%. Is preferred.

  The glass material of the present invention may contain the following components in the glass composition in addition to the above components.

  MgO, CaO, SrO, BaO and ZnO are components that enhance the chemical durability and the quantum yield. The content of MgO + CaO + SrO + BaO + ZnO is preferably 0 to 10%, more than 0 to 10%, 0.5 to 5%, and particularly preferably 1 to 4%. When the content of MgO + CaO + SrO + BaO + ZnO is too large, the glass becomes thermally unstable, and the glass tends to be devitrified at the time of melting or firing.

  The preferred content of each component of MgO, CaO, SrO, BaO and ZnO is as follows.

  Among MgO, CaO, SrO, BaO and ZnO, MgO is a particularly effective component for enhancing chemical durability and quantum yield. The content of MgO is preferably 0 to 10%, more than 0 to 10%, 0.5 to 5%, particularly preferably 1 to 4%. When the content of MgO is too large, the glass becomes thermally unstable, and the glass tends to be devitrified during melting or firing.

  CaO is a component that enhances chemical durability and quantum yield. The content of CaO is preferably 0 to 10%, 0 to 5%, 0.1 to 4%, particularly 1 to 4%. When the content of CaO is too large, the glass becomes thermally unstable, and the glass tends to be devitrified at the time of melting or firing.

  SrO is a component that enhances chemical durability and quantum yield. The content of SrO is preferably 0 to 10%, 0 to 5%, 0.1 to 4%, particularly 1 to 4%. When the content of SrO is too large, the glass becomes thermally unstable and the glass tends to be devitrified at the time of melting or firing.

  BaO is a component that enhances chemical durability and quantum yield. The content of BaO is preferably 0 to 10%, 0 to 5%, 0.1 to 4%, particularly 1 to 4%. When the content of BaO is too large, the glass becomes thermally unstable and the glass tends to be devitrified during melting or firing.

  ZnO is a component that enhances chemical durability and quantum yield. The content of ZnO is preferably 0 to 10%, 0 to 5%, particularly 0.1 to 4%. When the content of ZnO is too large, the glass becomes thermally unstable, and the glass tends to be devitrified at the time of melting or firing.

B ₂ O ₃ is a component that thermally stabilizes the glass to suppress devitrification. The content of B ₂ O ₃ is preferably 0 to 5%, particularly 0 to 3%. When the content of B ₂ O ₃ is too large, the chemical durability and the quantum yield tend to be reduced.

  SnO is a component that enhances the quantum yield. The content of SnO is preferably 0 to 5%, and more preferably 0 to 0.1%. When the content of SnO is too large, the glass becomes thermally unstable and the glass tends to be devitrified at the time of melting or firing.

F ₂ is a component that enhances the quantum yield. The content of F ₂ is preferably 0 to 30%, 0 to 25%, 0 to 20%, particularly 0 to 10%. When the content of F ₂ is too large, the glass becomes thermally unstable, and the glass tends to be devitrified at the time of melting, and the chemical durability tends to be reduced.

SiO ₂ is a component that thermally stabilizes the glass to suppress devitrification. The content of SiO ₂ is preferably 0 to 5%, particularly 0 to 3%. When the content of SiO ₂ is too large, phase separation is likely to occur.

Na ₂ O and K ₂ O are components that lower the melting temperature of glass. The content of Na ₂ O + K ₂ O is preferably 0 to 10%, and more preferably 0 to 5%. When the content of Na ₂ O + K ₂ O is too large, the glass becomes thermally unstable, and the glass tends to be devitrified at the time of melting, and the chemical durability tends to be reduced. Here, “Na ₂ O + K ₂ O” means the total content of Na ₂ O and K ₂ O.

The preferred contents of Na ₂ O and K ₂ O are as follows.

Na ₂ O is a component that lowers the melting temperature of glass. The content of Na ₂ O is preferably 0 to 10%, particularly 0 to 5%. When the content of Na ₂ O is too large, the glass becomes thermally unstable, and the glass tends to be devitrified at the time of melting, and the chemical durability tends to be reduced.

K ₂ O is a component that lowers the melting temperature of glass. The content of K ₂ O is preferably 0 to 10%, particularly 0 to 5%. When the content of K ₂ O is too large, the glass becomes thermally unstable, and the glass tends to be devitrified at the time of melting and the chemical durability tends to be reduced.

Yb ₂ O ₃ is a component that enhances the quantum yield. The content of Yb ₂ O ₃ is preferably 0 to 5%, 0 to 3%, and particularly 0 to 0.3%. When the content of Yb ₂ O ₃ is too large, the glass becomes thermally unstable and the glass tends to be devitrified at the time of melting.

Fe ₂ O ₃ , Bi ₂ O ₃ , Cr ₂ O ₃ , Er ₂ O ₃ , Nd ₂ O ₃ , V ₂ O ₅ , CuO, Dy ₂ O ₃ , Ho ₂ O ₃ , Tm ₂ O ₃ , CoO etc. In order to cause a decrease in quantum yield due to coloring, it is preferable that the content of each is 0.2% or less, particularly, substantially not contained.

  In the present invention, "does not substantially contain" means not intentionally containing as a raw material, and does not exclude even the inclusion of inevitable impurities. More objectively, it means that the content is less than 0.1%.

Sb ₂ O ₃ can be added as a fining agent. However, the content of Sb ₂ O ₃ is preferably 0.1% or less, in particular, substantially not contained, in order to avoid a decrease in quantum yield due to coloring or in consideration of environmental load.

  It is preferable not to contain PbO in consideration of environmental load.

In addition to the above components, other components such as GeO ₂ , TiO ₂ , La ₂ O ₃ , Lu ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ , Nb ₂ O ₅ etc. are added to the glass composition up to 5% each You may

  Next, a method of producing the glass material of the present invention will be described.

First, a predetermined amount of glass raw material prepared to have a desired composition is weighed and uniformly mixed. As a glass raw material, an oxide, a phosphoric acid compound, a fluoride, a chloride etc. can be used. In addition, it is preferable to use the raw material which is the state of the valence which emits fluorescence regarding Ce, Eu, Pr, and Tb which are components which emit fluorescence. Specifically, for example, Ce that emits fluorescence in a trivalent state preferably uses a raw material such as Ce ₂ O ₃ or CeF ₃ .

  The mixed glass material is placed in a melting vessel and melted at 1000-1400 ° C. for 30 minutes to 5 hours until a homogeneous glass is obtained. The melting atmosphere is preferably an inert atmosphere. The inert atmosphere may be any of nitrogen, argon or helium atmosphere, but a nitrogen atmosphere is particularly preferable in terms of low cost. When it is melted in an inert atmosphere, oxidation of Ce or the like is easily suppressed, so that the glass material tends to emit fluorescence. Moreover, when melting in the atmosphere, in order to suppress oxidation of Ce and the like, it is preferable to put a reducing agent such as metal aluminum, ammonium salt, carbon of 1000 ppm or less into the raw material. When the melting is performed in an inert atmosphere, it is preferable to put the above-mentioned reducing agent in the raw material in order to further suppress the oxidation of Ce and the like. As the melting vessel, platinum, quartz glass, alumina or the like can be used, but it is preferable that the melting vessel is platinum because quartz glass and alumina are easily dissolved in the glass and it becomes difficult to obtain a desired glass composition.

  Next, after casting molten glass, a glass material is obtained by annealing at 300 to 700 ° C. for 1 to 10 hours in order to remove distortion in the glass. In order to obtain a desired shape, the obtained glass material may be subjected to processing such as cutting and polishing.

  Hereinafter, the present invention will be described based on examples, but the present invention is not limited to these examples.

  Table 1 shows an example of the present invention and a comparative example, respectively.

  First, a glass material was prepared so as to have the glass composition shown in Table 1, then placed in a platinum crucible and melted at 1100 to 1300 ° C. for 1 to 2 hours. After the molten glass was poured out into a carbon mold, annealing was performed at 440 ° C. for 1 hour to obtain a glass material.

  The quantum yield of the obtained sample was measured using a quantum yield measurement apparatus (Quantaurus-QY manufactured by Hamamatsu Photonics K.K.). The results are shown in Table 1.

As shown in Table 1, No. 1 as an example. The glass of 1 to 6 had a high quantum yield of 81 to 91%. On the other hand, No. 1 which is a comparative example. The glass of 7 was not vitrified because the content of Al ₂ O ₃ was too large. Also, no. The glass of 8 had a low quantum yield of 3% because it contained no Al ₂ O ₃ .

  The glass material of the present invention is suitable as a phosphor and a scintillator.

Claims (5)

P ₂ O ₅ 40-80%, Li ₂ O 0 more than 50%, Al ₂ O ₃ 0 more than 15%, Ce ₂ O ₃ + EuO + Pr ₂ O ₃ + Tb ₂ O ₃ more than 0%-10% in mol% A glass material characterized by containing. The glass material according to claim 1, further comprising MgO + CaO + SrO + BaO + ZnO 0 to 10%, B ₂ O ₃ 0 to 5%, SnO 0 to 5%, F ₂ 0 to 30% in mol%. . The glass material according to claim 1 or 2, wherein the proportion of ⁶ Li to total Li is 95% or more in mol%.   The glass material according to claim 1, which is used as a phosphor.   The glass material according to any one of claims 1 to 4, which is used as a scintillator.