JP2006152089A - Luminescent material, piezoelectric body, electrostriction body, ferroelectric body, electroluminescent body, stress luminescent body, and manufacturing process of these - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new luminescent material which emits light by deformation caused by externally imposed mechanical forces such as friction, shear, and impact. <P>SOLUTION: The luminescent material contains mixed crystals in which more than one crystal structure exists such as a crystal having at least two or more crystal structures out of zinc oxide sulfide of a wurtzite mineral structure, zinc sulfide of a cubic crystal or a wurtzite mineral structure and manganese oxide of a cubic crystal and a crystal expressed by general formulas: (Ca<SB>1-x</SB>A'<SB>x</SB>)<SB>y</SB>Ba<SB>1-y</SB>TiO<SB>3</SB>, (Mg<SB>1-x</SB>A'<SB>x</SB>)<SB>y</SB>Ba<SB>1-y</SB>TiO<SB>3</SB>, and (Sr<SB>1-x</SB>A'<SB>x</SB>)yBa<SB>1-y</SB>TiO<SB>3</SB>(0.0001≤x≤0.05: 0.005≤y≤0.995: A' is a rare earth element selected from the group consisting of Dy, La, Gd, Ce, Sm, Y, Nd, Tb, Pr, and Er). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a novel light-emitting material, piezoelectric body, electrostrictive body, ferroelectric body, electroluminescent body, stress light-emitting body, and methods for producing them, which emit light when mechanical external force is applied.

  The phenomenon of emitting light by applying an external stimulus is well known as a fluorescence phenomenon. The fluorescent substance that emits fluorescence is used in a wide range including illumination lamps and displays. Examples of the external stimulus that causes the phosphor to emit light include ultraviolet rays, electron beams, X-rays, radiation, electric fields, and chemical reactions. In recent years, the inventors of the present invention have developed stress-stimulated luminescent materials that emit light when mechanical external force is applied and evaluation methods thereof.

  Specifically, a stress light-emitting material having a spinel structure, a corundum structure, or a β-alumina structure (see Patent Document 1), a stress light-emitting material of a silicate (see Patent Document 2), and a high-intensity stress light emission of a defect-controlled aluminate A test piece made of a body (see Patent Document 3), a multicolor stress-stimulated luminescent material (see Patent Document 4), a composite material containing an epoxy resin, and a coating film of the composite material, such as compression, tension, friction, torsion, etc. A method of evaluating stress luminescence characteristics by applying mechanical force (see Patent Document 5), an oxide, sulfide, selenide having a structure in which a wurtzite structure and a zincblende structure coexist, A high-luminance mechanoluminescence material (see Patent Document 6) composed mainly of telluride has been developed.

  The stress-stimulated illuminant can emit light repeatedly semipermanently with a luminance that can be confirmed with the naked eye. And it becomes possible to measure the stress distribution in a structure by using these stress luminescent materials. As such a measuring method, for example, a method of measuring stress or stress distribution using a stress illuminator, and a measuring system (see Patent Document 7), a mechanical external force is directly converted into an optical signal and transmitted. A light emitting head, a remote switch system using the light emitting head, and the like (see Patent Document 8) and the like can be mentioned.

As for a barium titanate (BaTiO ₃ ) -based fluorescent material, a red light emitting material obtained by adding aluminum (Al) to strontium titanate added with Pr, Al to which praseodymium ions are added (SrTiO ₃ : Pr ³⁺ ). (See Non-Patent Document 1), calcium titanate (CaTiO ₃ ) with praseodymium ions added (see Non-Patent Document 2), barium titanate (BaTiO ₃ ) with CaO added (see Non-Patent Document 3) And (Ba _0.90 Ca _0.10 ) (Ti _0.75 Zr _0.25 ) O ₃ (see Non-Patent Document 4) and the like have been reported.
JP 2000-119647 (April 25, 2000) JP 2000-313878 (released on November 14, 2000) JP 2001-49251 (released February 20, 2001) JP 2002-194349 (released July 10, 2002) JP2003-292949 (released on October 15, 2003) JP-A-2004-43656 (published on February 12, 2004) JP 2001-215157 (Aug. 10, 2001) JP 2004-77396 (published March 11, 2004) Shinji Okamoto et al., JOURNAL OF APPLIED PHYSICS, VOLUME 86, NUMBER10, 5594p-5597p, November 15, 1999, American Institute of Physics PT Diallo et al., Journal of Alloys and Compounds 323-324 (2001), 218p-222p, ELSEVIER Tsai-Fa et al., JOURNAL OF APPLIED PHYSICS, VOLUME 67, NUMBER15, 1042p-1047p, January 15, 1990, American Institute of Physics XG Tang et al., APPLIED PHYSICS LETTERS, VOLUME 85, NUMBER6, 991p-993p, August 9, 2004, American Institute of Physics Bernard Jaffe et al., “PIEZOELECTRIC CERAMICS”, 91p-95p, 1971, ACADEMIC PRESS

However, as described in Non-Patent Document 5, even if Ca is added to barium titanate (BaTiO ₃ ), there is a problem that the improvement of the Curie point is small and the dielectric constant is greatly reduced. . There have been no reports on electrostriction, piezoelectricity, stress luminescence, and electroluminescence regarding the mixed phase of barium titanate (BaTiO ₃ ) -based fluorescent materials.

  Zinc sulfide (ZnS) is a high-efficiency phosphor matrix. In particular, zinc sulfide to which manganese ions are added and those to which a pair ion of aluminum and silver is added are known as strong yellow light emitters and green light emitters. ing. Zinc oxide (ZnO) is also known as a light emitter matrix. However, these matrixes are unsuitable as red phosphors.

Further, as described in Non-Patent Document 1, although it has been found that the emission intensity is increased by adding Pr ions and Al ions to SrTiO ₃ , this phosphor emits electroluminescence at room temperature. In addition, there is no stress luminescence and no piezoelectricity.

  The present invention provides a novel red illuminant and a novel illuminant that not only emits light by ultraviolet excitation but can simultaneously exhibit stress luminescence, electroluminescence, and piezoelectricity. It is aimed.

  As a result of intensive research, the present inventors have realized that a new light emitter can be realized by making a mixed phase in which a plurality of crystal structures coexist, and that a luminescent substrate is utilized and light emission is achieved. By controlling the crystal environment that easily emits light at the center, it was found that the light emission intensity in stress light emission, ultraviolet excitation light emission, and electric field excitation was strong, and that it was possible to realize a multifunctional light emitter having piezoelectricity, and completed the present invention. It came to do.

  That is, the light-emitting material of the present invention is a light-emitting material that emits light when a mechanical external force is applied in order to solve the above problems, and includes a mixed phase in which a plurality of crystal structures are mixed. It is characterized by. As described above, a light-emitting material capable of emitting light that cannot be realized with a single crystal structure can be obtained by using a mixed phase composed of a plurality of crystal structures. In the present invention, “mixed phase” means that a plurality of crystal structures can be confirmed by X-ray crystal diffraction (XRD) measurement, that is, the result of XRD measurement corresponds to a plurality of crystal structures. The peak is obtained and is different from the solid solution.

  In the luminescent material of the present invention, the mixed phase is composed of at least two kinds of crystals from a crystal structure of zinc oxide having a wurtzite structure, cubic or wurtzite structure zinc sulfide, and cubic manganese oxide. It is a composite crystal having a structure. With this configuration, it is possible to obtain a red light emitter that cannot be realized by using one of zinc oxide, zinc sulfide, and manganese oxide alone or two of them. That is, a novel red light emitting material can be realized by using a mixed phase represented by the general formula xZnO + yZnS + zMnO.

  In the luminescent material of the present invention, a part of metal ions constituting the mixed phase may be substituted with other metal ions. In this case, the other metal ions different from the metal ions constituting the mixed phase are preferably Te ions. Thereby, it becomes possible to greatly improve the intensity of red light emission of the light emitting material of the present invention. The Te ions are preferably in the range of 0.1 mol or more and 5 mol or less with respect to 100 mol of the metal ions constituting the mixed phase.

  In order to solve the above-described problems, the light-emitting material of the present invention has a mixed phase of barium titanate having a tetragonal structure, calcium titanate having an orthorhombic structure, magnesium titanate having a rhombohedral structure, and cubic. It is characterized in that it contains at least two kinds of crystal structures of strontium titanate. In this case, a part of the metal ions constituting the mixed phase may be replaced with other metal ions.

In addition, the light-emitting material of the present invention has a general formula (Ca _1−x A ′ _x ) _y Ba _1−y TiO _3, (Mg _1−x A ′ _x ) _y Ba _1−y TiO _3, and (Sr _{1− x} A ′ _x ) yBa _1-y TiO ₃ (0.0001 ≦ x ≦ 0.05, 0.005 ≦ y ≦ 0.995, A ′ is Dy, La, Gd, Ce, Sm, Y, Nd, Tb , Pr, Er), and a rare earth element selected from the group consisting of Pr, Er.

  With the above structure, a light-emitting material having both light-emitting property and piezoelectricity that emit light by applying stress or an electric field can be obtained. As the rare earth element shown as A ′, praseodymium (Pr) is most preferably used.

The light emitting material of the present invention, ferroelectric tetragonal _{Ba 1-x} Ca x TiO3: the Pr solid solution (0 <x <0.23), orthorhombic paraelectric _{Ba y Ca 1-y} A mixed phase composed of TiO ₃ : Pr solid solution (0.9 <y <1) may be used.

  In the luminescent material of the present invention, the luminescence intensity may be proportional to the magnitude of the mechanical external force.

  In the luminescent material of the present invention, A ′ is Er or Pr, and it is preferable that the blending amount of Er or Pr and the blending amount of Ca are optimized.

  The Ca ratio is preferably in the range of 40% to 80%, or the Ca ratio is preferably in the range of 1% to 35%. More preferably, the Ca ratio is in the range of 55% to 65%, or the Ca ratio is in the range of 25% to 35%.

  The light-emitting material of the present invention has a plurality of crystal phases having different sizes, and among the plurality of crystal phases, at least one crystal phase has a large particle size, and at least one crystal phase has a large particle size. It is characterized by having a smaller particle size, and the crystal phase having a smaller particle size is uniformly dispersed among the particles of the crystal phase having a larger particle size.

In this case, the crystal phase of the barium titanate has a large particle size, and the crystal phase of the calcium titanate has a small particle size, and the calcium titanate crystal phase of the small particle size has a large particle size of barium titanate. It may be uniformly dispersed between the grains of the size crystal phase. Alternatively, the crystal phase of manganese oxide has a large particle size, and the crystal phase of zinc sulfide and zinc oxide has a small particle size. The zinc particle of zinc sulfide and zinc oxide crystal phase of small particle size have large particles of manganese oxide. It may be uniformly dispersed between the grains of the size crystal phase.

  In order to solve the above problems, the piezoelectric body of the present invention is characterized by including a mixed phase in which a plurality of crystal structures are mixed.

  In the piezoelectric body of the present invention, the mixed phase has at least one of tetragonal barium titanate, orthorhombic calcium titanate, rhombohedral magnesium titanate, and cubic strontium titanate. It is preferable that two or more types are included. In this case, a part of the metal ions constituting the mixed phase may be replaced with other metal ions.

The piezoelectric body of the present invention have the general formula _{(Ca 1-x A 'x} ) y Ba 1-y TiO 3, (Mg 1-x A' x) y Ba 1-y TiO 3, and _{(Sr 1-x} A ' _x ) yBa _1-y TiO ₃ (0.0001 ≦ x ≦ 0.05, 0.005 ≦ y ≦ 0.995, A ′ is Dy, La, Gd, Ce, Sm, Y, Nd, Tb, Pr , A rare earth element selected from the group consisting of Er). In this case, in the above general formula, Ca ion is 0.21-
It is preferable to have a mixed phase structure which is a composition contained within the range of 0.40.

  In order to solve the above problems, the electrostrictive body of the present invention is characterized by including a mixed phase in which a plurality of crystal structures are mixed.

The electrostrictive body of the present invention preferably has an electrostriction of 170% or more, assuming that the electrostriction of the BaTiO ₃ ceramic is 100%. Moreover, it is preferable that an electrostriction characteristic is 0.26% or more.

  In the electrostrictive body of the present invention, the mixed phase is composed of tetragonal barium titanate, orthorhombic structure calcium titanate, rhombohedral structure magnesium titanate, and cubic structure strontium titanate. It is preferable that at least two or more types are included.

Ibitsutai collector of the present invention have the general formula _{(Ca 1-x A 'x} ) y Ba 1-y TiO 3, (Mg 1-x A' x) y Ba 1-y TiO 3, and _{(Sr 1-x} A ′ _x ) yBa _1-y TiO ₃ (0.0001 ≦ x ≦ 0.05, 0.005 ≦ y ≦ 0.995, A ′ is Dy, La, Gd, Ce, Sm, Y, Nd, Tb, It may be made of a rare earth element selected from the group consisting of Pr and Er. In this case, in the above general formula, Ca ion is 0.21-
It is preferable to have a mixed phase structure which is a composition contained within the range of 0.40.

Ferroelectric present invention, in order to solve the above problems, the general formula _{(Ca 1-x A 'x} ) y Ba 1-y TiO 3, (Mg 1-x A' x) y Ba 1-y TiO ₃ and (Sr _1-x A ′ _x ) yBa _1-y TiO ₃ (0.0001 ≦ x ≦ 0.05, 0.005 ≦ y ≦ 0.995, A ′ is Dy, La, Gd, Ce , Sm, Y, Nd, Tb, Pr, Er), and a composition containing Ca ions in a range of 0.21-0.40 in 1 mol. It is characterized by having a certain mixed phase structure.

  In order to solve the above problems, the electroluminescent material of the present invention is characterized in that it includes a mixed phase in which a plurality of crystal structures are mixed.

The electroluminescent material of the present invention has at least two kinds of crystal structures among the crystal structures of zinc oxide having a wurtzite structure, cubic sulfide or zinc sulfide having a wurtzite structure, and cubic manganese oxide. A composite crystal is preferable. The mixed phase has at least two kinds of tetragonal barium titanate, orthorhombic calcium titanate, rhombohedral magnesium titanate, and cubic strontium titanate. It is preferable that it is included.

Further, the electroluminescent material of the present invention have the general formula _{(Ca 1-x A 'x} ) y Ba 1-y TiO 3, (Mg 1-x A' x) y Ba 1-y TiO 3, and (Sr _{1 −x} A ′ _x ) yBa _1-y TiO ₃ (0.0001 ≦ x ≦ 0.05, 0.005 ≦ y ≦ 0.995, A ′ is Dy, La, Gd, Ce, Sm, Y, Nd, It may be composed of a rare earth element selected from the group consisting of Tb, Pr and Er. In this case, in the above general formula, it is preferable to have a mixed phase structure having a composition in which Ca ions are contained in a range of 0.5 to 0.80 in 1 mol.

In order to solve the above-described problems, the stress-stimulated luminescent material of the present invention has the general formula (Ca _1-x A ′ _x ) _y Ba _1-y TiO _3, (Mg _1-x A ′ _x ) _y Ba _1-y. TiO ₃ and (Sr _1-x A ′ _x ) yBa _1-y TiO ₃ (0.0001 ≦ x ≦ 0.05, 0.005 ≦ y ≦ 0.995, A ′ is Dy, La, Gd, Ce , Sm, Y, Nd, Tb, Pr, Er), and a composition in which 1 mol of Ca ions is contained within a range of 0.5-0.80. It is characterized by having a certain mixed phase structure.

  The above-described luminescent material, piezoelectric material, electrostrictive material, ferroelectric material, electroluminescent material, or stress luminescent material of the present invention is obtained by a method including a step of mixing raw materials in a ratio of a mixed phase in which a plurality of crystal structures are mixed. Can be manufactured.

The manufacturing method of this invention is good also as making the vacuum degree of the said raw material container into the 10 ^<-1 > Pa or more at the time of manufacture.

  Moreover, it is good also as adding sulfur during the synthesis | combination of the manganese oxide crystal | crystallization which added two zinc. In this case, sulfur and tellurium may be added simultaneously.

  The luminescent material, piezoelectric material, electrostrictive material, ferroelectric material, electroluminescent material, and stress luminescent material of the present invention include a mixed phase in which a plurality of crystal structures are mixed. By this mixed phase, a new light emitting material capable of emitting red light, a piezoelectric body, an electrostrictive body, a ferroelectric body, an electric field light emitting body, and a stress light emitting body can be realized.

In addition, the light emitting material, piezoelectric body, electrostrictive body, ferroelectric body, electroluminescent body, and stress light emitting body of the present invention are represented by the general formula (Ca _1−x A ′ _x ) _y Ba _1−y TiO _3, (Mg _1-x A ′ _x ) _y Ba _1-y TiO ₃ and (Sr _1-x A ′ _x ) yBa _1-y TiO ₃ (0.0001 ≦ x ≦ 0.05, 0.01 ≦ y ≦ 0. 99, A ′ includes a mixed phase composed of a rare earth element selected from the group consisting of Dy, La, Gd, Ce, Sm, Y, Nd, Tb, Pr, and Er. Accordingly, a light emitting material, a piezoelectric body, an electrostrictive body, a ferroelectric body, an electroluminescent body, and a stress light emitting body having both light emitting property and piezoelectricity that emit light by applying a stress or an electric field can be obtained.

  Accordingly, the light emitting material of the present invention can be easily realized in the three-way conversion of electricity, machine, and light as well as the application fields of the light emitting material (light emitting body) and the piezoelectric body so far. Can be developed for applications such as new sensors, actuators, new display devices, and amusement equipment.

[Embodiment 1]
The applicants of the present invention have proposed “stress luminescence”, and aim at remote stress sensing and visualization of stress distribution using a material that emits light by mechanical action. Up to now, we have developed stress-stimulated luminescent materials with different luminescent colors. For example, the defect control type SrAl ₂ O ₄ : Eu finds that the light emission intensity and the stress are linearly proportional in the elastic deformation region, and obtains a strong green stress light emission intensity that can be visually observed even during the day.

  However, since the red stress illuminant has low visual sensitivity, a stress illuminant exhibiting sufficient visual strength has not been developed yet. Therefore, as a result of intensive studies aimed at developing a high-efficiency red-stressed luminescent material that can be visually observed, it has been found that this can be realized by the configuration described below.

  The light-emitting material of this embodiment includes a mixed phase in which a plurality of crystal structures are mixed. The mixed phase includes zinc oxide having a wurtzite structure, cubic sulfide or zinc sulfide having a wurtzite structure, and cubic. It includes a mixed phase in which a crystal structure with crystalline manganese oxide is mixed.

Moreover, a part of the metal ions constituting the mixed phase may be replaced with another metal ion different from the metal ions constituting the mixed phase. Examples of the other metal ions include Te, Sb, Sn, Mn, Cu, and Ag. Among these, Te ⁴⁺ ions are preferable.

Te ⁴⁺ is preferably in the range of 0.01 mol to 20 mol and more preferably in the range of 0.1 mol to 5 mol with respect to 100 mol of the metal ions constituting the mixed phase. Preferably, it is in the range of 1 mol or more and 3 mol or less.

  Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited thereto.

In order to determine the origin (matrix) of the red luminescence phase, the inventors of the present invention put a raw material powder in a quartz sample tube for a series of combinations of ZnS, ZnO, MnS, MnTe, Mn, and Te. The sample tube was placed in a vacuum furnace, evacuated to a high vacuum, and then grown at a temperature higher than the synthesis temperature.
The crystal structure of the synthesized sample was identified by the X-ray diffraction method, and the luminescence phase was identified by examining the luminescence characteristics.

  The phase of the novel chemical species identified in this way is a mixed phase in which two crystal phases of zinc sulfide and zinc oxide always coexist, and in addition, a plurality of crystal structures including manganese oxide (Mn + 2O) coexist. Is formed. And in order to improve the light emission in a red luminescence phase significantly, it discovered that the effect of Te was remarkable. Below, the preparation method and luminescence characteristic of these materials are demonstrated.

〔experimental method〕
After unnecessary gases such as oxygen and water are discharged from the reaction tank, the reaction tank is evacuated to a high vacuum, and filled with an inert gas such as Ar to a target pressure (1 Pa to 1 atm). A sealed atmosphere control type solid crystal synthesis reactor was designed that can control the synthesis reaction by sealing and firing. A closed atmosphere control type solid crystal synthesis reactor (hereinafter referred to as “synthesis reactor”) was used to synthesize compound crystals containing components that are very easily sublimated, such as sulfur and tellurium. The raw materials of the luminescent material are weighed at a predetermined ratio and mixed uniformly in a mortar, and then packed into a quartz tube having an inner diameter of 10 mm × length of 10 cm, and both ends of the tube are plugged with quartz wool. These quartz tubes are inserted into the synthesis reaction apparatus and heated for 10 hours to 100 hours at a temperature at which the atmospheric temperature of the reaction layer becomes 600 ° C. to 1200 ° C. for several hours. As a result of repeating many trial and errors, the optimum temperature (atmosphere temperature in the reaction vessel) and the heating time were 10 hours at 850 ° C. Also, under similar firing conditions, a high vacuum sealed ampoule (0.1 P
Some experiments using pressures below a) were also conducted.

For structural analysis, a Rigaku Rint 2000 powder X-ray diffractometer was used. A Jasco FP-6500 spectrofluorophotometer was used for photoluminescence and thermoluminescence measurements. A Jasco V-570 UV-VIS-IR spectrophotometer was used for the measurement of light absorption.

In this example, a reagent having a purity of 99.9% or more was used. As a result of experiments using various reagents, ZnO _0.60 MnS _0.40 (0.6ZnO · 0.4MnS) was obtained as yellow luminescence, and yellow was added by adding a small amount of MnTe. It was found that it can be converted to red luminescence.

[Experimental results and discussion]
The samples obtained by adjusting according to the method described above and the measurement results are shown in Table 1 below.

  Sample 1 in Table 1 above was manufactured in a high-vacuum sealed ampoule, and the other samples 2 to 5 were manufactured by a sealed atmosphere control type solid synthesizer. What is synthesized with a high vacuum sealed ampoule further increases the emission intensity. In addition to the samples described in Table 1 above, samples used only for comparative consideration were also prepared using a sealed atmosphere control type solid synthesizer. In the following description, each sample is distinguished using the composition of the raw material instead of the XRD phase.

  FIG. 1 shows an X-ray diffraction (hereinafter referred to as “XRD” as appropriate) pattern of Samples 1 to 5 shown in Table 1. In addition, the peak indicated by the arrow in the figure is attributed to the phase indicated to the left of the arrow.

  Among the phases shown in FIG. 1, it is known that none of the ZnTe phase, the manganese oxide (Mn + 2O) phase, and the ZnO phase alone show the yellow or red luminescence shown in Table 1. Yes. Among the phases shown in the figure, only the ZnS phase exhibits yellow luminescence alone. The ZnS phase is wurtzite zinc sulfide, which is a 2H or 10H phase—a multilayer repeating structure (superlattice structure).

  In the crystalline phase of the wurtzite zinc sulfide phase 10H, the length of the C-axis of the crystal increases five times that of the 2H phase, and the structure becomes cylindrical in the multilayer repeating structure. The phase observed in sample 1 is 2H, while in other samples it is 10H. This increase in the columnar C-axis is considered to be involved in fixing the light emission center Te.

In order to investigate the role of ZnS, ZnS _0.96 MnTe _0.04 , ZnS _0.90 MnTe _0.10 , ZnS _0.93 ZnTe _0.03 MnTe _0.04 , ZnS _0.91 Mn _0.03 Te _{0. In a} closed atmosphere control type solid synthesizer, a sample of a mixture at a raw material ratio of ₀₆ and ZnS _0.94 Te _0.06 is used.
It was over. As a result, 2H phase (see FIG. 2) and 10H phase (see FIG. 3) of the ZnS phase were obtained. However, the observed luminescence was very small, and in some cases, the latter (10H phase) was not detected (see FIG. 1). Therefore, the samples 2 to 5 shown in Table 1 were fired at 850 ° C. to 1200 ° C. for 10 hours. It is considered that the cause of the red luminescence is not the ZnS single phase.

  Further, FIG. 9 shows an excitation spectrum and an emission spectrum of Sample 1, FIG. 10 shows an emission spectrum of Samples 2 to 5, and FIG. 11 shows an excitation spectrum. The excitation spectrum and emission spectrum shown in FIGS. 9, 10, and 11 are different, and the emission center wavelength of sample 1 is about 582 nm (yellow), while samples 2 to 5 are about 640 nm (red). . In addition, the band gaps of the substances shown in FIGS. 9, 10, and 11 were significantly different from those of ZnS (see FIG. 8) as shown in Table 2 and FIG. That is, the band gap of zinc sulfide is completely different from the band gap of the high luminescence phase obtained by the combination of ZnO—MnS—MnTe shown in Table 1 and FIG.

In addition, phases other than ZnS may cause luminescence. Here, ZnO is known to emit green luminescence, but it is not known to emit strong red or yellow luminescence together with Te or Mn. In a sample prepared with an apparent ratio of ZnO _0.5 MnS _0.5 , high yellow luminescence is observed, and by adding Te, red luminescence is emitted. However, there was no ZnO phase peak in the XRD pattern of this sample.

FIG. 4 shows an XRD pattern obtained by measuring a ZnO _0.5 MnS _0.5 sample. As shown in the figure, no peak of the ZnO phase is observed in the XRD pattern of the sample of ZnO _0.5 MnS _0.5 . From the above, it is considered that ZnO is not the cause of yellow luminescence in the sample 1 shown in FIG. 1 and the ZnO _0.5 MnS _0.5 sample shown in FIG.

The next possible cause of the luminescence is Mn + 2O. However, this pure Mn + 2O phase shows no luminescence. FIGS. 5 and 6 summarize the correlation between the emission characteristics of the mixed-phase phosphor containing manganese oxide composed of various ratios and the crystallinity of manganese oxide. Here, one important notable point is that the PL (Photoluminescence) intensity is as shown in FIG. 5 with respect to the XRD peak intensity of the [200] plane of the Mn + 2O phase as seen with other similar materials. There is a serious relationship. If there is no peak of the manganese oxide phase, strong light emission cannot be obtained. In addition, when a certain threshold is exceeded, strong light emission is observed. That is, the coexistence of the manganese oxide phase is indispensable for obtaining strong light emission. (FIG. 5). For strong light emission, it is most preferable that the crystal phase of manganese oxide and zinc sulfide coexist, and further the crystal phase of zinc oxide coexists.

The second important point to note is that the XRD diffraction angle (eg, [200] plane) of the manganese oxide crystal phase is always greater than 40.547 for a pure manganese oxide single phase. This suggests lattice shrinkage. In an atmosphere-sealed synthesizer, the ionic radius of all elements that can be incorporated into Mn + 2O is such that sulfur, tellurium, and zinc can be lattice-shrinkable by substitution with manganese ions or oxygen ions. Therefore, the only possibility of lattice contraction was the replacement of a substantial number of Zn and manganese. FIG. 6 shows the variation of the photoluminescence intensity (PL intensity) with respect to 2θ (theta) of the [200] plane of Mn + 2O because the ratio of the mixed phase varies, and the emission characteristics can be obtained only by the zinc substitution amount. This indicates that the coexistence of other crystal phases is also important.

From FIG. 6, it is clear that there is an optimum degree of incorporation in order to emit photoluminescence that is visually observable. Manganese oxide (Mn + 2
O) Either a single phase or a hybrid with manganese oxide (Mn + 2O) in which Zn is dissolved is an indispensable element for generating luminescence. And this phase can be easily made in two ways.

The first method is to thermally decompose MnCO ₃ . According to the method of pyrolyzing and burning MnCO ₃ alone, a single phase that does not emit luminescence can be obtained without causing a shift to a high angle in the diffraction angle as shown in FIG. Moreover, when MnO ₃ is mixed with ZnO and then thermally decomposed, a clear shift to a high angle is observed in the diffraction peak, but a product without luminescence is obtained.

  In the second method, a mixture (mixture) of Mn + 2O and a considerable amount of Zn can be obtained by mixing ZnO and metal Mn and synthesizing them by heat treatment. In this case, a clear transition of the diffraction angle was observed, but a product without luminescence was obtained.

  When sulfur was added during the synthesis of the manganese oxide crystal to which the above two zincs were added, yellow luminescence was obtained. Furthermore, red luminescence was obtained when sulfur and tellurium were added simultaneously.

  It is considered essential for yellow or red luminescence to add a more suitable amount of S / Te to Mn + 2O mixed with a suitable amount of sufficient Zn.

FIG. 7 shows a graph in which light absorption, which is a characteristic of the base semiconductor, is measured for samples 1 to 5 shown in Table 1. As is clear from the figure, these semiconductors have a characteristic band gap absorption in the wavelength region of 500 to 700 nm, and the light absorption spectrum exhibits a characteristic shoulder shape absorption in the long wavelength region. Indicated. Absorption in the wavelength region of 300 nm to 400 nm is due to the ZnS phase and the ZnO phase.

The band gaps obtained for the samples 1 to 5 are shown in Table 2. As shown in FIG. 7, as the Te content increases, the shoulder shape of absorption becomes sharper, but the luminescence decreases. As described above, these samples contain a mixed phase in which ZnO, ZnS, and Mn + 2O phases coexist.

The band gap results obtained as described above do not reflect the main phases ZnS or ZnO. FIG. 8 shows the absorption characteristics of the Mn + 2O phase obtained with the raw materials of MnCO ₃ and ZnO _0.6 Mn _0.4 . Comparison of the absorption properties of the luminescence sample with the absorption properties of the ZnO, ZnS and Mn + 2O phases shows that the luminescence is due to Mn + 2O.

However, the phases of MnCO ₃ and ZnO _0.6 Mn _0.4 described above are both non-luminescent, which is considered to be due to the fact that S and Te are not added (doped). Since these additions significantly improve the absorption in the long wavelength region, it is considered that a new hybrid containing S and Te contributes to luminescence.

  FIG. 9 shows the excitation spectrum and emission spectrum of the yellow luminescence sample of Sample 1, and FIG. 10 shows a graph showing the emission spectra of Samples 2 to 5 of red luminescence.

  9 and 10 are excitation and emission spectra of a typical sample when the Te content is increased. The center wavelength of the emission spectrum shifted to the longer wavelength side as the Te content increased. Further, even when the Te content was low or not containing Te, visible yellow light emission was observed as shown in FIG. And PL intensity decreased as Te content increased.

  FIG. 11 shows excitation spectra of red luminescence samples 2 to 5. As shown in the figure, in the excitation light spectrum, the peak of the excitation light moves to the longer wavelength side as the Te content increases. In samples with a high Te content, a clear decrease occurs in the short wavelength region. And PL intensity is also decreasing with the increase in Te content.

  As already mentioned, Samples 2 to 5 contain ZnO, ZnS, and Mn + 2O phases. And ZnO known for green luminescence is not the cause of the photoluminescence (PL) observed in this example. On the other hand, ZnS exhibits yellow luminescence while adding Mn. Also, ZnS was observed to emit weak red luminescence in a thin film doped with 3% Mn and 6% Te.

Several samples containing Mn and Te in addition to ZnS as a matrix were prepared. FIG. 12 shows a PL spectrum of a sample containing 4% MnTe (ZnS _0.96 MnTe _0.04 ). As shown in the figure, the luminescence of this sample was weak, and the excitation spectrum showed a plurality of excitation bands in the wavelength range of 400 nm to 500 nm. Most luminescence arises from excitation wavelengths between about 490 nm and 500 nm. The band gap of these samples is about 2.94 ev, which is close to the band gap of ZnS.
This is different from the light emission by the mixed phase as shown in FIG. 10 and FIG. 11, and shows that the light emission is by a completely different phase.

[Mechanoluminescence]
FIG. 13 shows ML (mechanoluminescence, stress emission) when a force of 1000 N is applied to ZnO _0.6 MnS _0.4 and ZnO _0.5 MnS _0.5 emitting yellow luminescence.
Indicates a signal. FIG. 14 shows ML signals when a force of 1000 N is applied to ZnO _0.6 MnS _0.35 MnTe _0.05 and ZnO _0.6 MnS _0.37 MnTe _0.03 emitting red luminescence. Yes. As shown in FIGS. 13 and 14, it can be seen that all of the above samples exhibit stress luminescence.

[Thermoluminescence]
FIG. 15 shows the results of low-temperature photoluminescence of ZnO _0.6 MnS _0.35 MnTe _0.05 prepared at two temperatures (850 ° C. and 950 ° C.). In general, the PL intensity increases at a low temperature, but FIG. 14 shows that in the sample prepared at 950 ° C., the luminescence intensity decreases as the temperature decreases.

FIG. 16 and FIG. 17 show glow curves when the temperature is increased at different speeds for the ZnO _0.6 MnS _0.35 MnTe _0.05 samples prepared at 850 ° C. and 950 ° C. From FIG. 16 and FIG. 17, those prepared at 950 ° C. showed 3 traps, whereas those prepared at 850 ° C. showed only 2 traps.

[Summary of this example]
The sample with high yellow luminescence is a sample as a raw material of ZnO _0.6 Mns _0.4 produced in a vacuum sealed condition or a closed atmosphere control type solid synthesizer under the condition of 850 ° C. to 900 ° C. there were. In the preparation stage, the luminescence color changed to red by adding several percent of MnTe to the raw material of the sample. The addition of 0.1-5% Te is indispensable for synthesizing a strong red luminescent material with a raw material containing Zn, Mn, O, and S elements.

  The phases observed by XRD were ZnO, ZnS and Mn + 2O. A hybrid containing a high concentration of MnTe or ZnTe was similarly prepared. Since luminescence was observed in a plurality of samples not containing the ZnO phase, the luminescence by the ZnO phase alone can be excluded from the cause of the yellow and red luminescence.

  It was recognized that the PL intensity has a correlation with both the peak of XRD intensity and the peak position of Mn + 2O. Presumably, in addition to the addition of sulfur (S), lattice shrinkage of the Mn + 2O phase, which is thought to be caused by mixing with zinc (Zn), is likely a necessary condition for generating strong red luminescence. The optical band gap of about 2.0 eV observed in the sample of this example is considered to be due to the Mn + 2O phase.

  ZnS and Mn + 2O are formed simultaneously from the interaction of ZnO and MnS, and the presence of the ZnS phase is another requirement for generating strong luminescence. Further, the luminescence is enhanced by the coexistence of the ZnO phase.

  Many samples containing the desired phases ZnS and Mn + 2O showed weak luminescence regardless of the shape of the emission and excitation spectra. The band gaps of these samples were close to those of ZnS and did not match the band gaps of the highly luminescent samples at all.

Since the sample exhibiting the highest stress luminescence was prepared using a high vacuum sealed ampoule, the stress luminescence was improved by increasing the degree of vacuum. The degree of vacuum is preferably 10 ⁻¹ Pa or higher, that is, the pressure in the high vacuum sealed ampoule is preferably less than 10 ⁻¹ Pa.

[Embodiment 2]
In the present embodiment, electrical / mechanical / light conversion in Pr ^{3 +} -added (doped) BaTiO ₃ —CaTiO ₃ ceramic will be described.

  A so-called intelligent material or smart material is a material capable of realizing a detecting function and an operating function like other similar materials. In recent years, materials having such characteristics have attracted attention. FIG. 18 shows the electric field, mechanical stress or strain, and the mutual conversion action with light. In the figure, the physical interaction between electric field, stress or strain, and light includes piezoelectric or inverse electrostriction, electroluminescence, and electricity. It shows an optical effect (Electro-optic effect), a photostriction effect (Photostriction), and stress luminescence (Mechanoluminescence).

  Until now, research and application of such materials have often been considered by combining two parameters. For example, electro-mechanical interaction (piezoelectric and electrostrictive effect), mechanical-optical interaction (stress emission and photostriction), and electro-optical interaction (electroluminescence and electrooptic effect). As functional materials and devices have evolved significantly, the development of materials and devices with more functions is eagerly desired.

In the present embodiment, by finding the piezoelectric effect, electrostrictive effect, stress luminescence, and electroluminescence of BaTiO ₃ —CaTiO ₃ ceramic added with (doped) Pr ³⁺ which is a multifunctional material, The result of examining the interconversion between mechanical energy and optical energy is shown.

  Electrostrictive (ES) actuators convert electrical energy directly into mechanical energy, and the position of the actuator can be adjusted by the applied voltage, so optics, astronomy, fluid control, precision machining, etc. Used in a wide variety of areas.

Stress luminescence in a broad sense (mechanoluminescence, sometimes referred to as ML) is caused by destruction or deformation when mechanical stress is applied to a solid. Such luminescence is referred to as fractoluminescence, as appropriate. FL) and deformation luminescence (referred to as DL as appropriate). Among these, DL is more suitable for practical use since it is non-destructive.

  New DL materials and methods for investigating their properties have been developed and methods for evaluating DL materials have been improved. Such materials are now being used for visualization of stress distributions, high performance sensors and self-diagnostic systems. The stress light emission in this embodiment means such nondestructive deformation light emission. Electroluminescence (EL) is a phenomenon in which electrical energy is converted into light energy without generating thermal energy, and is widely used in flat panel displays.

The three effects (ES, ML, and EL) described above can be simultaneously realized by a mixed phase ceramic of BaTiO ₃ —CaTiO ₃ to which Pr ³⁺ is added, as will be described later. Application of voltage causes mechanical strain and light emission, and mechanical stress causes electrical signals (piezoelectric and counterelectrostrictive effects) and light emission. By using this type of multifunctional material, complex detection and actuation system applications that can respond simultaneously to electrical, physical and optical signals can be realized.

Barium titanate (BaTiO ₃ ) discovered about 60 years ago was the first perovskite ferroelectric / piezoelectric material that was the subject of research. In the field of piezoelectricity / electrostriction, zirconate It was replaced by lead titanate. In recent years, however, lead-free materials have begun to attract attention as the movement to protect the global environment increases. Therefore, research on materials mainly composed of BaTiO ₃ has become active again, and single crystals and doped ceramics with high electrostriction have been obtained.

It is known that by replacing Ca ²⁺ with Ba ²⁺ of BaTiO ₃ , a Ba _1-x Ca _x TiO ₃ solid solution is obtained when _x is in the range of 0.21 or less. This only slightly changes the Curie point (cubic paraelectric to tetragonal ferroelectric transition temperature), but the tetragonal to orthorhombic transition temperature is significantly reduced. The lowering of the tetragonal-orthorhombic transition temperature in this way is very preferable for improving the temperature stability of piezoelectricity / electrostriction and applying it to practical use.

In a state where the solubility limit (x = 0.21) is exceeded, the region until the proportion of CaTiO _{3 in} the whole reaches 90 mol% is an insoluble region. A material (mixed phase) in which two crystal phases coexist in such a region has not been noticed until now. However, a material composed of a composition having a solid solution limit has attracted attention as a solid solution having a solid solution limit in that it has a possibility of exhibiting a further excellent function. Indeed, lead, such as Pb (Zn _1/3 Nb _2/3 ) TiO ₃ —PbTiO ₃ (PZN-PT) and Pb (Mg _1/3 Nb _2/3 ) TiO ₃ —PbTiO ₃ (PMN-PT) The composition of the ultra-high strain material containing as the main component is located in the vicinity of the boundary (morphotropic phase boundary (MBP)) where the phase change occurs. High strain is considered to be caused by conjugation of two equivalent energy states, tetragonal and orthorhombic.

On the other hand, calcium titanate (CaTiO ₃ ) added (doped) with trivalent praseodymium (Pr ³⁺ ) has been reported to exhibit strong red luminescence at room temperature. However, Pr ³⁺ doped (1-x) BaTiO ₃ xCaTiO ₃ (x> 0.21) hybrids or mixed phase materials containing multiple crystalline phases are very good electromechanical, stress luminescent and electric fields The thing which shows luminescent property was discovered for the first time by this invention.

In addition, BaTiO ₃ and CaTiO ₃ are both inferior in the above characteristics alone or do not have the above characteristics at all.

Luminescent material of this _{embodiment, (Ca 1-x Pr x} ) y Ba 1-y TiO 3, (Mg 1-x A 'x) y Ba 1-y TiO 3, (Sr 1-x Pr x) yBa _1-y TiO ₃ (0.0001 ≦ x ≦ 0.05, 0.01 ≦ y ≦ 0.99), and Pr is Dy, La, Gd, Ce, Sm, Y, It may be a rare earth element selected from the group consisting of Nd, Tb, Pr and Er.

  Hereinafter, the present embodiment of the present invention will be described in detail with reference to examples, but the present invention is not limited thereto.

In this example, in a mixed phase in which a plurality of crystal phases coexist, Pr ³⁺ doped (1-x) BaTiO ³⁻ xCaTiO ₃ ceramic (x = 0.25 to 0.30) in the vicinity exceeding the solubility limit, The electrostrictive (ES) strain of 0.264%, 176% higher than the electrostriction of BaTiO ₃ ceramic, strong red stress luminescence (mechanoluminescence ML) and electroluminescence (electroluminescense (EL)) Observed. This Pr ³⁺ addition (1
^-X) BaTiO 3- xCaTiO ₃ ceramic, ferroelectric tetragonal _Ba 0.77 _Ca 0.23 TiO3: Pr solid solution, orthorhombic standard dielectric _Ba 0.1 _Ca 0.9 TiO ₃ : A mixed phase ceramic composed of Pr solid solution.

The augmented ES and newly discovered ML and EL found in the above ceramics are the solid solution mainly composed of BaTiO ₃ doped with (doped) Pr ³⁺ and the solid solution mainly composed of CaTiO _3. It is not allowed. These are the large ionic polarization in Ba _0.1 Ca _0.9 TiO ₃ : Pr and the ferroelectric region (ferroelectric region in Ba _0.77 Ca _0.23 TiO ₃ : Pr in the mixed phase ceramic. This is caused by the strong interaction between the domains (ferroelectric domains).

〔experimental method〕
In this example, Ba _1-xy Ca _x Pr _y TiO ₃ (x = 0, 0.20, 0.23, 0.25, 0.30, 0.40, 0.50, 0.60, Based on the stoichiometric composition of 0.70, 0.80, 0.90, 0.95, 1.0, y = 0.002), using a solid phase reaction method, Pr ³⁺ doped BaTiO ₃ —CaTiO _Three ceramics were prepared. More specifically, what was weighed to a predetermined composition ratio was prepared by adding ethanol, mixing uniformly using a ball mill, and heating at 1400 ° C. for 4 hours in an oxygen atmosphere. Hereinafter, the composition of the sample, [(1-x) BaTiO3 -xCaTiO 3]: showing in simplified as Pr. In addition, it will be expressed as BCT- ●● where appropriate using a two-digit number ●● after the decimal point of x. For example, Ba _0.68 Ca _0.30 TiO ₃ : Pr _0.02 is designated as BCT-30.

Figure 19 [(1-x) BaTiO3 -xCaTiO 3]: the value of Pr in the x, showing an XRD pattern of a sample was varied in the range of 1.0 to 0.2. As shown in the figure, in the XRD of the samples with X = 1.0 and 0.95, only the orthorhombic peak indicated by O is recognized in the figure, and the samples with X = 0.20 and 0.23 In the XRD, only the tetragonal peak indicated by T in the figure is recognized, whereas in the XRD of the sample with X = 0.25 to 0.90, the orthorhombic and tetragonal peaks are recognized. As a result of structural analysis, the sample of x <0.25 is a single-phase tetragonal Ba _1-x CaxTiO ₃ : Pr solid solution, and the sample of 0.90 <x is a single-phase tetragonal Ba _1-x CaxTiO ₃ : Samples of Pr solid solution with 0.25 ≦ x ≦ 0.90 are tetragonal Ba _0.77 Ca _0.23 TiO ₃ : Pr solid solution and orthorhombic Ba _0.1 Ca _0.9 TiO ₃ : Pr solid solution It became clear that it was a mixed phase of the two-phase coexistence state. The solid solution limit of Ca was improved from 0.21 to 0.23 by dissolving Pr.

FIG. 20 shows an XRD spectrum and a micrograph obtained by conducting a structural analysis on a sample (BCT-30) where x = 0.30. As shown in the XRD spectrum of the figure, the peak T on the (110) plane of the tetragonal Ba _0.77 Ca _0.23 TiO ₃ : Pr solid solution and the orthorhombic Ba _0.1 Ca _0.9 TiO ₃ : Pr There is a peak on the (121) plane of the solid solution, and it can be clearly confirmed that two phases coexist. Further, the black small particles in the photograph are orthorhombic Ba _0.1 Ca _0.9 TiO ₃ : Pr solid solution (calcium titanate), and the white large particles are tetragonal Ba _0.77 Ca _0.23 TiO ₃ : Pr (titanium). Small particles are uniformly dispersed at the grain boundaries of the large particles.

Pr ³⁺ can replace both Ba ²⁺ and Ca ^{2+ in} a two-phase coexisting state. Pr ^{3+ enhances the} ferroelectric properties by replacing Ba ^{2+ in the} ferroelectric tetragonal phase, and supplies red emission centers by replacing Ca ²⁺ in the orthorhombic phase.

FIG. 21 shows the electrostriction (ES) characteristics of BCT-20, 23, 25, 30, 40, and 50. As shown in the figure, the sample in the mixed phase state of this example showed excellent electrostrictive characteristics. In particular, both BCT-25 and 30 in the vicinity of the solubility limit in the two-phase region, which are in a two-phase coexistence state, drew a beautiful butterfly curve. This agrees with the hysteresis loop drawn by the polarization graph with respect to the electric field shown in FIG. Further, it can be seen from the hysteresis characteristics shown in FIG. 22 that the ferroelectric characteristics of BCT-20, 23, 25, 30, 40, and 50 are excellent.

BCT-25 (x = 0.25) achieved strong electrostriction of about 0.264% in a driving electric field of ± 55 kV / cm and Hz. The value of this electrostriction is 176% higher than the electrostriction of the BaTiO ₃ ceramic. That is, if the electrostriction of the BaTiO ₃ ceramic is 100%, the electrostriction of BCT-25 is 176%.

[(1-x) BaTiO3-xCaTiO3]: In the two-phase region (0.25 ≦ x ≦ 0.90) of the Pr sample, BCT-60 with x = 0.60 realized strong ML and EL emission. FIG. 23 shows ML (Mechanoluminescence) of BCT-60. FIG. 23 (a), (b)
Shows BCT-60 pellets emitting red ML observable with the naked eye while applying pressure, and FIG. 23 (c) shows that ML intensity is proportional to the applied pressure. . In FIG. 23C, the upper curve indicates the ML intensity, and the lower curve indicates the magnitude of the pressure applied to the BCT-60 pellet. In addition, although the result of BCT-60 was specifically described here, it was confirmed that all the samples in the two-phase region (0.25 ≦ x ≦ 0.90) showed the same properties as described later. is doing. These properties are not present at all in BaTiO ₃ or CaTiO ₃ doped with Pr ³⁺ . Further, the above-mentioned [(1-x) BaTiO3- xCaTiO3]: phenomenon has been confirmed for the two-phase region (0.25 ≦ x ≦ 0.90) of Pr samples single phase SrAl ₂ doped with previously ^{Eu 2+} Although it is the same as the stress luminescence phenomenon that the applicant has already confirmed for O ₄ , the crystal phase is completely different and the emission spectrum is also different.

  The electroluminescence characteristic (EL) of BCT-60 is shown in FIG. As shown in the figure, when the AC power supply (60 Hz) is set to “on”, the EL intensity attenuates greatly and then stabilizes while slightly changing depending on the electric field. Thus, BCT-60 has been shown to have excellent electroluminescence characteristics. In addition, the enlarged view in the figure expands the range of Time = 3100-3125. FIG. 25 shows the relationship between the EL intensity and the magnitude of the electric field. As shown in the figure, it can be seen that the EL intensity increases as the electric field increases.

  FIG. 26 shows the electroluminescence characteristics (EL) of BCT-30. As shown in the figure, it can be seen that BCT-30, as well as BCT-60, exhibits excellent electroluminescence characteristics. Thus, the mixed phase is excellent in electroluminescence characteristics.

  Next, in order to characterize the emission of ML and EL, the spectrum of ML and EL was compared with the spectrum of photoluminescence (PL). FIG. 27 shows a graph in which ML, EL, and PL spectra are overlapped for BCT-30. FIG. 28 shows a graph in which the same spectrum is overlaid for BCT-60.

As shown in FIG. 27, the ML and EL spectrum peaks of BCT-30 are both located at 618 nm and coincide with each other, but are slightly shifted from the PL peak (612 nm). This fact indicates that the Pr ³⁺ doped BaTiO ₃ —CaTiO ₃ ceramic ML, EL, and PL emit light from the same emission center as the Pr ³⁺ doped CaTiO ₃ . That is, it shows that ML, EL, and PL of Pr ³⁺ doped BaTiO ₃ —CaTiO ₃ ceramic emit light by Pr ^{3+ 1} D ₂ ⁻³ H ₄ transition in a host mainly composed of CaTiO ₃ − Yes.

The phenomenon described above is strong between the ionic polarization of Ba _0.1 Ca _0.9 TiO ₃ : Pr and the ferroelectric domain in the Ba _0.77 Ca _0.23 TiO ₃ : Pr. This can be explained using a model of interaction. First, we investigated the elements that control ES, ML and EL. Electrostriction (ES) is believed to arise from non-180 ° domain rotation driven by an external electric field. Both ML and EL are also strongly associated with piezoelectrics and dislocations in the solid, which will show strong ML and EL if they have a luminescent center with a specific efficiency. .

In this example, [(1-x) BaTiO ₃ −xCaTiO ₃ ]: Pr (0.25 ≦ x0.90) ceramic is tetragonal Ba _0.77 Ca _0.23 TiO ₃ : Pr solid solution, and oblique It is a mixed phase containing a tetragonal Ba _0.1 Ca _0.9 TiO ₃ : Pr solid solution. In a wide temperature range (at least in the range of −180 ° C. to 120 ° C.), the former is ferroelectric and the latter is paraelectric.

CaTiO ₃ exhibits initial ferroelectricity, ie ferroelectric-like properties. Ba _0.1 Ca _0.9 TiO _3: Pr is, CaTiO _3: because it has a large ionic polarization than Pr, CaTiO _3: shows the Pr has a dielectric constant (about 145) larger dielectric constant than (about 200) .

In the mixed phase ceramic (0.25 ≦ x0.90) of this example, Ba _0.1 Ca _0.9 TiO ₃ : Pr particles are dispersed in the ceramic. That is, in the figure showing the photograph of FIG. 20B, the dark particles Ba _0.1 Ca _0.9 TiO ₃ : Pr particles are light-colored particles in FIG. Ba _0.77 Ca _0.23 TiO ₃ : Dispersed in Pr particles. And the ionic polarization of Ba _0.1 Ca _0.9 TiO ₃ : Pr particles is associated with the non-180 ° domains in the surrounding Ba _0.77 Ca _0.23 TiO ₃ : Pr particles. Such polarization enhances the polarizability and domain rotation capability of the ceramic in the presence of an external electric field.

  Therefore, a large electrostriction can be obtained in a mixed phase ceramic in which x = 0.25 near the solubility limit. In addition, the electrostriction of the sample with x = 0.30 maintained a large value of 0.11% despite the considerable amount of non-ferroelectric portions.

Since Pr ^{3 +} -added BaTiO ₃ and Ba _1-x CaxTiO ₃ solid solution (x <0.25) have weak luminescence, [(1-x) BaTiO ₃ −xCaTiO ₃ ]: Pr (0.25 ≦ x ≦ 0. 90) The strong red light emission in the mixed phase is considered to be strongly related to the Ba _0.1 Ca _0.9 TiO ₃ : Pr phase.

In the mixed phase ceramic (see FIG. 20), particles of Ba _0.1 Ca _0.9 TiO ₃ : Pr and Ba _0.77 Ca _0.23 TiO ₃ : Pr are strongly bonded in the three-dimensional direction, and It interacts in three dimensions on the nano and micrometer scales. Such a state is not found in commercial products. In a commercially available product, a thin film having ferroelectricity and light emitting property has physical contact and interaction of particles constituting the film all along a one-dimensional direction.

When mechanical pressure or electric field is applied to the ceramic, the ferroelectric (also piezoelectric) Ba _0.77 Ca _0.23 TiO ₃ : Pr particles are Ba _0.1 Ca _0.9 TiO ₃ : Pr. A surface charge is supplied with respect to and dislocation of Ba _0.1 Ca _0.9 TiO ₃ : Pr particles. And Ba _0.1 Ca _0.9 TiO ₃ : Pr particles and Ba _0.77 C
Due to the strong interaction with the a _0.23 TiO ₃ : Pr particle, the carrier at the emission center is excited to a high energy level. As described above, ML or EL emission is seen when an appropriate transition occurs.

  Of the measurement results of BCT-60, 70, 80, 90, 95, and 100, the excitation spectrum is shown in FIG. 29, and the emission spectrum is shown in FIG. BCT-95 was found to show the highest fluorescence. 29, Em: to 612 nm is an excitation spectrum when the emission wavelength is 612 nm (Em = Emission = light emission), and Ex: to 336 nm is an emission spectrum when the excitation wavelength is 336 nm. Yes.

Further, among the measurement results of BCT-20, 25, 30, 40, and 50, the coercive electric field (Ec) and the remanent polarization (Pr) are shown in FIGS. 31 (a) and 31 (b). As shown in the figure, it can be seen that all the samples of this example have a low coercive electric field Ec and a high remanent polarization Pr. Moreover, BCT-20,23,25,30,40,50 and _[BaTiO 3]: for Pr (BT-pure), shows the results of the strain electric induction was measured in Figure 32. As shown in the figure, the sample which is a mixed phase of the present example shows an electrically induced strain much higher than [BaTiO ₃ ]: Pr, and it can be seen that the mixed phase exhibits excellent characteristics.

  FIG. 33 shows a graph showing the relationship between the applied voltage (Electric field) and the electroluminescence intensity (EL Intensity) for BCT-30, 50, 60, and 70. According to the figure, it can be seen that all of BCT-30, 50, 60, and 70 emit light at a low voltage.

FIG. 34 shows the results of measuring the electrostrictive characteristics of the sample with the Ca ratio x changed under the conditions of 1 Hz and 50 kV / cm. As shown in the figure, in the case of a mixed phase sample in which the Ca ratio is 25% to 90% (mol%), the amount of Pr and Ca can be optimized to be improved more than the single phase. did it. In particular, a very high electrostrictive property of 0.264% was observed in a sample of 30% Ca located on the peak indicated by A in the mixed phase exceeding the phase solubility limit. FIG. 35 shows the results of measuring the fluorescence characteristics (ultraviolet light emission) of the samples with different values. As shown in the figure, the fluorescence characteristics can be greatly improved by optimizing the blending amounts of Pr and Ca.

  FIG. 36 shows the result of measuring the electroluminescence of the sample with the Ca ratio x changed. As shown in the figure, by optimizing the blending amounts of Pr and Ca, the electroluminescence function could be expressed by a mixed phase normal sample that was not a single phase. In particular, a high electroluminescence function was observed in a mixed-phase sample in which the Ca ratio x having a peak indicated by B in the figure is in the vicinity of about 40-80%. Further, the maximum electroluminescence function was observed in the mixed phase sample having a Ca ratio x of about 60%.

  FIG. 37 shows the result of measuring the stress luminescence for the sample with the Ca ratio x changed. As shown in the figure, the Ca ratio x corresponding to the electrostriction peak A in FIG. 34 is about 30%, and the Ca ratio x corresponding to the electroluminescence peak B in FIG. There is a peak of stress luminescence at the position of 60%. From this, it was found that the stress luminescence of the sample of this example was achieved by a synergistic effect of electrostriction / piezoelectricity and electroluminescence.

[Summary of this example]
In summary, the [(1-x) BaTiO ₃ −xCaTiO ₃ ]: Pr ceramic in the vicinity of the mixed phase region (0.25 ≦ x ≦ 0.30) exceeding the solubility limit has high electrostriction, stress luminescence, and All of the electroluminescence was realized. In the biphasic region (0.25 ≦ x ≦ 0.90), a large ion polarization of Ba _0.1 Ca _0.9 TiO ₃ : Pr and a Ba _0.77 Ca _0.23 TiO ₃ : Pr domain Is considered to function as an important factor in improving ES characteristics and producing high ML characteristics and high EL characteristics. Such characteristics are not observed in the solid solution of Pr ³⁺ doped BaTiO ₃ and Pr ³⁺ added CaTiO ₃ .

  The following knowledge was obtained by examining the composition dependence of electrostrictive properties (ES), stress luminescence (ML) intensity, and electroluminescence (EL) intensity. The electrostriction was decreased by increasing the Ca ratio to be greater than 40%, and about 0.043% in the sample with x = 0.50. From this, it can be said that a high Ca ratio is inconvenient for electrostrictive use.

  Further, when x increases to 0.40 or more, the ML intensity and the EL intensity start to increase and show a maximum in the vicinity of 0.60. This indicates that in the biphasic region (0.25 ≦ x ≦ 0.90), a material having a high Ca ratio is useful for the use of a material having high ML strength and EL strength. However, when x is around 30%, high electrostriction and stress luminescence are exhibited, and at the same time, relatively high electroluminescence is exhibited.

  The two crystalline phases of the ferroelectric material and the non-ferroelectric material are a coexisting hybrid (two-phase mixed phase), and the sample of this example having a plurality of functions can be obtained from a wide variety of materials. It can be said that it is very useful for the development of new multifunctional materials and materials having high single functions (such as those having high ES characteristics, ML strength or EL strength).

Comparative example

Shown in Example 2 of the present invention, to form a mixed phase in the range of 0.25 ≦ x ≦ 0.90 [(1 -x) BaTiO3-xCaTiO 3]: For comparison with Pr, BaSrTiO ₃ + Pr + Al Samples of the system were prepared and examined for fluorescence, stress luminescence, and electroluminescence. A sample weighed to a predetermined composition ratio was mixed with ethanol, mixed using a ball mill, and prepared by baking at 1400 ° C. for 4 hours in an oxygen atmosphere.

In the BaSrTiO ₃ + Pr + Al sample prepared as described above, it was confirmed by observation with a scanning electron microscope and XRD measurement that all of the samples in which the Sr ratio was changed were not mixed phases but a single crystal structure. confirmed. For this reason, it was necessary to add Pr or Al in order to cause the sample of this comparative example to emit light. Therefore, XRD measurement was performed on those prepared with Al addition amounts of 1% and 3%. As a result, in the sample to which Al was added, a peak shift was recognized as compared with the sample to which Al was not added, and it was found that Al was dissolved in the crystal structure of the sample of the comparative example.

  Further, it was confirmed that the sample to which Al was added emitted fluorescence, and the fluorescence intensity of the sample having a Sr ratio of 40% was maximized. However, the sample of this comparative example did not develop stress luminescence and electroluminescence.

  The light emitting material of the present invention can be applied to uses as a novel light emitting material that emits light by stress, a piezoelectric body, an electrostrictive body, a ferroelectric body, an electric field light emitting body, and a stress light emitting body.

FIG. 4 shows powder X-ray diffraction patterns of Examples of the present invention, and the peak indicated by the arrow of each pattern is a typical X-ray diffraction pattern (PDF crystal structure database based on the phase indicated to the left of the arrow). Represents a peak that matches. ZnS. 90MnTe. It is the XRD pattern of the 2H phase of ZnS obtained about 10 samples. ZnS. 93 ZnTe. 03MnTe. It is the XRD pattern of 2H and 10H phase of ZnS obtained about 04 sample. ZnO. 5MnS. It is a graph which shows the XRD pattern obtained about 5 samples. It is a graph which shows distribution of PL intensity with respect to the intensity | strength of the peak (Mn + 2O [200] plane) of a XRD pattern. It is a graph which shows distribution of PL intensity with respect to the value of the peak position 2 theta of the [200] plane XRD pattern of Mn + 2O. 5 is a graph in which light absorption spectra are recorded for samples 1 to 5 shown in Table 1. The absorption spectrum of each of Mn +. 2O phase obtained from MnCO3 and _Zn 0.6 _{Mn 0.4} material is a graph showing with the absorption spectrum of the ZnS and ZnO. It is a graph which shows the spectrum of the excitation (excitation) and emission (emission) of the sample 1 of yellow luminescence. It is a graph which shows the spectrum of the emission of the samples 2-5 of red luminescence. It is a graph which shows the excitation spectrum of samples 2-5 of red luminescence. Is a graph showing exciting (excitation) and emission (emission) of 4% sample containing _{MnTe (ZnS} 0.96 MnTe _0.04). The _ZnO 0.6 _{MnS 0.4} and _ZnO 0.5 _{MnS 0.5} emits yellow luminescence, is a graph showing the ML (stress luminescent) signal when a force of 1000 N. The _ZnO 0.6 _MnS 0.35 _{MnTe 0.05} and _ZnO 0.6 _MnS 0.37 _{MnTe 0.03} emit red luminescence is a graph showing the ML signal when a force of 1000 N. For _ZnO 0.6 _MnS 0.35 _{MnTe 0.05} prepared in two temperatures (850 ° C. and 950 ° C.), is a graph showing the results of low-temperature photoluminescence. Was prepared at 850 ° _C., the sample of ZnO _0.6 MnS 0.35 _{MnTe 0.05,} is a graph showing the glow curve when the temperature is increased at different rates. Was prepared at 950 ° _C., the sample of ZnO _0.6 MnS 0.35 _{MnTe 0.05,} is a graph showing the glow curve when the temperature is increased at different rates. It is a figure which shows the correlation of an electric field, mechanical stress or distortion, and light. Is a graph showing the [(1-x) BaTiO3- xCaTiO 3] of x value sample XRD pattern was varied in the range of 1.0 to 0.2 in. The XRD spectrum and the micrograph which were obtained by conducting the structural analysis of BCT-30 are shown. It is a graph which shows the electrostriction (ES) characteristic of BCT-20, 23, 25, 30, 40, 50. It is a graph which shows the hysteresis characteristic (Ferroelectric hysteresis loop) of BCT-20, 23, 25, 30, 40, 50. 2 shows ML (Mechanoluminescence) of BCT-60, and (a) and (b) are diagrams of a BCT-60 pellet emitting red ML observable with the naked eye while pressure is applied, (c ) Is a graph showing that the ML intensity is proportional to the applied pressure. It is a graph which shows the electroluminescent characteristic (EL) of BCT-60. It is a graph which shows the relationship between the EL intensity | strength of BCT-60, and the magnitude | size of an electric field. It is a graph which shows the electroluminescent characteristic (EL) of BCT-60. It is the graph which overlapped and described the spectrum of ML, EL, and PL of BCT-30. It is the graph which overlapped and described the spectrum of ML, EL, and PL of BCT-60. It is a graph which shows the excitation spectrum of BCT-60,70,80,90,95,100. It is a graph which shows the emission spectrum of BCT-60,70,80,90,95,100. The measurement result of BCT-20, 25, 30, 40, 50 is shown, (a) is a graph which shows a coercive electric field (Ec), (b) is a graph which shows remanent polarization (Pr). BCT-20,23,25,30,40,50 and _[BaTiO 3]: for Pr (BT-pure), it is a graph showing the results of a strain electric induction was measured. It is a graph showing the relationship between the applied voltage and electroluminescence intensity about BCT-30, 50, 60, 70. It is a graph which shows the result of having measured the electrostriction characteristic on 1 Hz and 50 kV / cm conditions about the sample which changed the ratio x of Ca. It is a graph which shows the result of having measured the fluorescence characteristic (ultraviolet excitation light emission) about the sample which changed the ratio x of Ca. It is a graph which shows the result of having measured electroluminescence about the sample which changed the ratio x of Ca. It is a graph which shows the result of having measured stress luminescence about the sample which changed the ratio x of Ca.

Claims (39)

A luminescent material that emits light when mechanical external force is applied,
A luminescent material comprising a mixed phase in which a plurality of crystal structures are mixed.   The mixed phase is a composite crystal having at least two types of crystal structures among crystal structures of zinc oxide having a wurtzite structure, zinc sulfide having a cubic or wurtzite structure, and cubic manganese oxide. The luminescent material according to claim 1, wherein the luminescent material is provided.   The luminescent material according to claim 2, wherein a part of metal ions constituting the mixed phase is substituted with other metal ions.   The luminescent material according to claim 3, wherein the other metal ion is Te ion.   The luminescent material according to claim 4, wherein the Te ion is in a range of 0.01 mol to 5 mol with respect to 100 mol of the metal ions constituting the mixed phase.   The mixed phase contains at least two kinds of tetragonal barium titanate, orthorhombic calcium titanate, rhombohedral magnesium titanate, and cubic strontium titanate. The luminescent material according to claim 1.   The luminescent material according to claim 6, wherein a part of the metal ions constituting the mixed phase is substituted with other metal ions. Formula _{(Ca 1-x A 'x} ) y Ba 1-y TiO 3, (Mg 1-x A' x) y Ba 1-y TiO 3, and _{(Sr 1-x A 'x} ) yBa 1-y TiO ₃ (0.0001 ≦ x ≦ 0.05, 0.005 ≦ y ≦ 0.995, A ′ is selected from the group consisting of Dy, La, Gd, Ce, Sm, Y, Nd, Tb, Pr, Er The luminescent material according to claim 1, wherein the luminescent material is a rare earth element. Ferroelectric tetragonal _{Ba 1-x Ca x TiO3:} Pr solid solution (0 <x <0.23) and, orthorhombic paraelectric _{Ba y Ca 1-y TiO 3} : Pr solid solution (0.9 The light emitting material according to claim 1, wherein the light emitting material is a mixed phase composed of <y <1).   The luminescent material according to claim 1, wherein the luminescence intensity is proportional to the magnitude of the mechanical external force.   The light emitting material according to claim 8, wherein A 'is Er or Pr, and the blending amount of Er or Pr and the blending amount of Ca are optimized.   The light emitting material according to claim 8, wherein the Ca ratio is in the range of 40% to 80%.   The light emitting material according to claim 8, wherein the Ca ratio is in the range of 1% to 35%.   The light emitting material according to claim 8, wherein A 'is Pr. It has a plurality of crystal phases having different sizes, and among the plurality of crystal phases, at least one crystal phase has a large particle size, and at least one crystal phase has a particle size smaller than the large particle size. A light emitting material, wherein the crystal phase having a small particle size is uniformly dispersed among the particles having a crystal phase having a large particle size.   The barium titanate crystal phase has a large particle size, and the calcium titanate crystal phase has a small particle size. The small particle size calcium titanate crystal phase has a large particle size of barium titanate. The light emitting material according to claim 15, wherein the light emitting material is uniformly dispersed between the phase particles.   The crystal phase of manganese oxide has a large particle size, and the crystal phase of zinc sulfide and zinc oxide has a small particle size. The zinc particle of zinc sulfide and zinc oxide crystal phase of small particle size have a large particle size of manganese oxide. The light-emitting material according to claim 15, wherein the light-emitting material is uniformly dispersed between the grains of the crystal phase.   A piezoelectric body comprising a mixed phase in which a plurality of crystal structures are mixed.   The mixed phase contains at least two kinds of tetragonal barium titanate, orthorhombic calcium titanate, rhombohedral magnesium titanate, and cubic strontium titanate. The piezoelectric body according to claim 18.   20. The piezoelectric body according to claim 19, wherein a part of metal ions constituting the mixed phase is substituted with other metal ions. Formula _{(Ca 1-x A 'x} ) y Ba 1-y TiO 3, (Mg 1-x A' x) y Ba 1-y TiO 3, and _{(Sr 1-x A 'x} ) yBa 1-y TiO ₃ (0.0001 ≦ x ≦ 0.05, 0.005 ≦ y ≦ 0.995, A ′ is selected from the group consisting of Dy, La, Gd, Ce, Sm, Y, Nd, Tb, Pr, Er The piezoelectric body according to claim 18, wherein the piezoelectric body is made of a rare earth element. The piezoelectric body according to claim 21, wherein in the general formula, the piezoelectric body has a mixed phase structure having a composition in which Ca ions are contained within a range of 0.21 to 0.40 in 1 mol.   An electrostrictive body comprising a mixed phase in which a plurality of crystal structures are mixed. The electrostrictive body according to claim 23, wherein the electrostriction is 170% or more when the electrostriction of the BaTiO ₃ ceramic is 100%.   The electrostrictive body according to claim 23, wherein the electrostrictive characteristic is 0.26% or more.   The mixed phase contains at least two kinds of tetragonal barium titanate, orthorhombic calcium titanate, rhombohedral magnesium titanate, and cubic strontium titanate. The electrostrictive body according to claim 23. Formula _{(Ca 1-x A 'x} ) y Ba 1-y TiO 3, (Mg 1-x A' x) y Ba 1-y TiO 3, and _{(Sr 1-x A 'x} ) yBa 1-y TiO ₃ (0.0001 ≦ x ≦ 0.05, 0.005 ≦ y ≦ 0.995, A ′ is selected from the group consisting of Dy, La, Gd, Ce, Sm, Y, Nd, Tb, Pr, Er 24. The electrostrictive body according to claim 23, wherein the electrostrictive body is made of a rare earth element. 28. The electrostrictive body according to claim 27, wherein in the above general formula, the electrostrictive body has a mixed phase structure having a composition in which Ca ions are contained within a range of 0.21 to 0.40 in 1 mol. Formula _{(Ca 1-x A 'x} ) y Ba 1-y TiO 3, (Mg 1-x A' x) y Ba 1-y TiO 3, and _{(Sr 1-x A 'x} ) yBa 1-y TiO ₃ (0.0001 ≦ x ≦ 0.05, 0.01 ≦ y ≦ 0.99, A ′ is selected from the group consisting of Dy, La, Gd, Ce, Sm, Y, Nd, Tb, Pr, Er Rare earth element), and 1 mol of Ca
A ferroelectric having a mixed phase structure in which ions are contained in a range of 0.21 to 0.40.   An electroluminescent material comprising a mixed phase in which a plurality of crystal structures are mixed.   The mixed phase is a composite crystal having at least two types of crystal structures among crystal structures of zinc oxide having a wurtzite structure, zinc sulfide having a cubic or wurtzite structure, and cubic manganese oxide. 31. The electroluminescent material of claim 30, wherein the electroluminescent material is.   The mixed phase contains at least two kinds of tetragonal barium titanate, orthorhombic calcium titanate, rhombohedral magnesium titanate, and cubic strontium titanate. The electroluminescent material according to claim 30, wherein Formula _{(Ca 1-x A 'x} ) y Ba 1-y TiO 3, (Mg 1-x A' x) y Ba 1-y TiO 3, and _{(Sr 1-x A 'x} ) yBa 1-y TiO ₃ (0.0001 ≦ x ≦ 0.05, 0.005 ≦ y ≦ 0.995, A ′ is selected from the group consisting of Dy, La, Gd, Ce, Sm, Y, Nd, Tb, Pr, Er 31. The electroluminescent material according to claim 30, wherein the electroluminescent material is made of a rare earth element. 34. The electroluminescent material according to claim 33, wherein the general formula has a mixed phase structure having a composition in which Ca ions are contained within a range of 0.5 to 0.80 in 1 mol. Formula _{(Ca 1-x A 'x} ) y Ba 1-y TiO 3, (Mg 1-x A' x) y Ba 1-y TiO 3, and _{(Sr 1-x A 'x} ) yBa 1-y TiO ₃ (0.0001 ≦ x ≦ 0.05, 0.005 ≦ y ≦ 0.995, A ′ is selected from the group consisting of Dy, La, Gd, Ce, Sm, Y, Nd, Tb, Pr, Er A stress-stimulated luminescent material characterized by having a mixed phase structure having a composition in which Ca ions are contained within a range of 0.5 to 0.80 in 1 mol.   A method for producing a light-emitting material, a piezoelectric body, an electrostrictive body, a ferroelectric body, an electric field light-emitting body, or a stress light-emitting body according to any one of claims 1 to 35, wherein a mixed phase in which a plurality of crystal structures are mixed and A method for producing a light emitting material, a piezoelectric material, an electrostrictive material, a ferroelectric material, an electroluminescent material, or a stressed light emitting device, comprising a step of mixing raw materials in a ratio of 37. The light emitting material, piezoelectric material, electrostrictive material, ferroelectric material, electroluminescent material, or stress luminescence according to claim 36, wherein the vacuum degree of the raw material container at the time of manufacture is ^10-1 Pa or more. Body manufacturing method.   37. The light emitting material, piezoelectric material, electrostrictive material, ferroelectric material, electroluminescent material, or stress luminescence according to claim 36, wherein sulfur is added during the synthesis of the manganese oxide crystal to which two zincs are added. Body manufacturing method.   Furthermore, sulfur and tellurium are added simultaneously, The manufacturing method of the luminescent material of Claim 38, a piezoelectric material, an electrostrictive body, a ferroelectric material, an electroluminescent body, or a stress light-emitting body.

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