Persistent luminescence ceramic or glass-ceramic material

Abstract

The present invention relates to a ceramic or glass-ceramic material corresponding to one of the following formulas: [(Sr1-a1-b1 Xa1X'b1)1-e REe]12+c [(Al1-dYd)1-fMf]20+2c[(Si1-gZg)1-hMh]12-2cO66 formula (I) [(Sr12-a2-b2 Xa2X'b2)1-e REe][(Al1-dYd)1-fMf]20[(Si1-gZg)1-hMh]12O66 formula (II) in which: X represents at least one alkaline earth metal excluding barium, X' represents at least one alkaline earth metal, RE represents at least one element selected from the group consisting of rare earths, bismuth (Bi) and one of their combinations, Y represents at least one element selected from the group consisting of metalloids, of poor metals, non-metals and one of their combinations, M represents at least one transition metal, Z represents at least one element chosen from the group consisting of metalloids, non-metals and one of their combinations, 0 ≤ a1 ≤ 10 ≤ b1 ≤ 1 / 30 ≤ a2 ≤ 120 ≤ b2 < 120 ≤ c < 10 ≤ d < 1 e, f,g and h are greater than or equal to zero and strictly less than 1. Figure for the abstract: no figure.

Description

Title of the invention: Persistent luminescent ceramic or glass-ceramic material. TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to the field of ceramic or glass-ceramic materials, more particularly to ceramic or glass-ceramic materials used in optical applications, notably persistent luminescence. Description of the invention

[0002] Persistent luminescence refers to the ability of certain materials to continue emitting light after being exposed to a light source and after that source has been removed. These materials thus have the ability to capture a certain amount of energy, which they then charge, and release this energy in the form of light for periods of up to several hours.

[0003] Due to their ability to emit light for a prolonged period after exposure to a light source (UV, sunlight, etc.), these materials have applications in various fields such as signage, security, optical devices, biomedical imaging, jewelry, etc. However, despite strong demand, very few materials exhibiting these properties currently exist. Furthermore, the emission colors are currently very limited.

[0004] The most commonly used persistent luminescence materials are as follows:

[0005] Europium- and dysprosium-doped strontium aluminate (SrAl2O4) is the best-known commercial material (with various applications, notably in security, jewelry / aesthetics). It emits in the green (non-modulatable greenish color).

[0006] Europium-doped calcium aluminate CaAl2O4 emits in the blue.

[0007] The compound CaS which emits in the red, however this one is not chemically stable.

[0008] However, these materials are not transparent. Yet transparency is a necessary parameter for certain applications, particularly for certain optical applications. Currently, only a few cases of transparent materials with persistent luminescence have been reported in the scientific literature. However, these materials are generally glass-ceramics, which by definition contain crystals and glass. Only the crystals are responsible for persistent luminescence; therefore, these materials are not fully active. Furthermore, these materials are only synthesized on a laboratory scale because their production process is lengthy, expensive, and subject to high rejection rates.

[0009] Consequently, there is a real need to provide persistent luminescent materials that are both transparent and fully active, exhibiting new emission colors, and can be used for a variety of applications.

[0010] The present invention relates first to a ceramic or glass-ceramic material conforming to one of the following formulas:

[0011] [(Sri_abbi

[0012] formula (I)

[0013] [(Sr12_a2-b2 X^u REe][(Al1.dYd)1.fMf]20[(Si1.gZg)1.hMh]12O66

[0014] formula (II)

[0015] in which: - X represents at least one alkaline earth metal, excluding barium. - X' represents at least one alkaline earth metal, - RE represents at least one element chosen from the group consisting of rare earth elements, bismuth (Bi) and one of their combinations, - Y represents at least one element chosen from the group consisting of metalloids, post-transition metals, non-metals and one of their combinations, - M represents at least one transition metal, - Z represents at least one element chosen from the group consisting of metalloids, non-metals and one of their combinations, 0 < al < 1 0 <bl<l / 3 - 0 < a2 < 12 0 < b2 < 12 0 <c<l 0 <d<l - e, f, g and h are greater than or equal to zero and strictly less than 1.

[0016] For the purposes of this invention, "ceramic" means a polycrystalline inorganic material consisting of crystals, with a degree of crystallization between 98% and 100%, i.e. between 98% and 100% by volume of the crystalline material.

[0017] For the purposes of this invention, "vitroceramic" means an inorganic material consisting of a mixture of glass and crystals, with a degree of crystallization between 5 and 98%, i.e. between 5% and 98% by volume of the crystalline material.

[0018] It should be noted that in the context of this application, and unless otherwise stipulated, the ranges of values ​​indicated are understood to include the limits.

[0019] The material according to the invention is a strontium aluminosilicate whose composition can be modified by substituons and / or dopants.

[0020] Thus, strontium can be substituted by X and / or X'.

[0021] Advantageously, X represents at least one alkaline earth metal selected from the group consisting of Mg and Ca. Preferably, X represents calcium (Ca).

[0022] Advantageously, X' represents at least one alkaline earth metal selected from the group consisting of Mg, Ba and Ca. Preferably X represents barium (Ba).

[0023] Aluminium can be substituted by the variable Y as defined previously in formulas (I) or (II).

[0024] In the material of formula (I) or formula (II) Y represents at least one element chosen from the group consisting of metalloids, poor metals, non-metals and one of their combinations.

[0025] Advantageously, the metalloids are chosen from the group consisting of: B, Si, Ge, As, Sb. Preferably B (boron).

[0026] Advantageously, the low-grade metals are chosen from the group consisting of Zn, Ga, In and Sn. Preferably Ga (gallium).

[0027] Advantageously, the non-metals are chosen from the group consisting of phosphorus (P) and sulfur (S). Preferably P (phosphorus).

[0028] Advantageously, Y represents gallium and / or boron.

[0029] Silica can be substituted by Z.

[0030] In the material of formula (I) or formula (II) Z represents at least one element chosen from the group consisting of metalloids, non-metals and one of their combinations.

[0031] Advantageously, the metalloids are chosen from the group consisting of B, Ge, As, Sb, Te. Preferably Ge (germanium).

[0032] Advantageously, the non-metals are chosen from the group consisting of phosphorus (P), sulfur (S), and selenium (Se). Preferably phosphorus (P).

[0033] Advantageously, Z represents germanium (Ge).

[0034] Advantageously, the material according to the invention is doped with dopants chosen from the group consisting of rare earths, transition metals, bismuth (Bi) and one of their combinations.

[0035] The doping element, its concentration, and its oxidation state are chosen according to the desired optical properties of the material. This doping can be particularly advantageous for various applications in the field of optics, notably by imparting specific optical properties to the material, for example, luminescence. In particular, when doped, the material according to the invention exhibits persistent luminescence properties by emitting a blue color.

[0036] Advantageously, the rare earths are chosen from the group consisting of Eu, Gd, Ce, Ho, Yb, Dy, Pr, Nd, Tb, Er, Tm, Yb and one of their combinations. Preferably, Eu and / or Dy.

[0037] Advantageously, RE is chosen from the group consisting of Eu, Dy, Bi and one of their combinations.

[0038] Advantageously, when in formula (I) or (II) the number e is greater than zero, said material exhibits persistent luminescence.

[0039] Advantageously, the material according to the invention comprises a molar percentage of dopant of between 0.5% and 5%, preferably between 0.5% and 3%, more preferably between 1% and 2%.

[0040] Advantageously, M represents at least one transition metal selected from the group consisting of Ti, Cr, Mn, Fe, Co, Ni, Cu and one of their combinations. Preferably, M represents Cr (chromium).

[0041] Doping with transition metals makes it possible to introduce or improve the optical properties of the material such as emission color, the lifetime of persistent luminescence.

[0042] According to one embodiment, the material according to the invention is doped only with rare earths, in which case the material corresponds to formula (I) or (II) in which e is greater than zero, and f is equal to zero.

[0043] According to a second embodiment, the material according to the invention is doped only with transition materials, in this case the material corresponds to formula (I) or (II) in which e is equal to zero and f is greater than zero.

[0044] According to a third embodiment, the material according to the invention is doped with rare earths and with transition materials, in this case the material corresponds to formula (I) or (II) in which e and f are greater than zero.

[0045] Advantageously, said material corresponds to one of the following formulas:

[0046] [(Srl al bl CaalBabl)le REe]12+c [(All d iGad Bi)1_fMf]20+2c[(Sii-gGeg)1_hMh]12_2cO66

[0047] formula (the)

[0048] [(Sri2a2b2 Ca^Batzke REe][(AlidiGadBi)i_fMf]2o[(Sii_gZg)i_hMh]i2066

[0049] formula (lia)

[0050] in which: 0 <i<l - al, bl, c, d, e, f, g, h and M are as defined previously.

[0051] Advantageously, said material corresponding to formula (I) or formula (la) is chosen from the following materials: — Sri2+cAl2O+2cSi2-2cO66 “Sri2CacA12O+2cSil2-2eO66 — Sri2BacA12O+2cSil2-2cO66

[0052] with 0 < c < 1, preferably c is between 0.3 and 0.9.

[0053] Advantageously, said material corresponding to formula (II) or formula (lia) is chosen from the following materials: - Sri2-b2Bab2A12oSii2066 with 0 < b2 < 12, preferably b2 is between 1.2 and 3.6; - Sri2-a2Caa2A12oSii2066 with 0 < a2 < 12, preferably a2 is between 1.2 and 3.6; - Sri2-eREeA12oSii2066 with RE representing Eu and / or Dy and with 0 < e < 1, preferably e is between 0.12 and 0.24.

[0054] Advantageously, said material corresponds to the formula Sr^A^oSi^Oee-

[0055] Advantageously, the material according to the invention is transparent.

[0056] For the purposes of this invention, "transparent" means that one can see through the material (within the visible spectrum). This qualitative notion of transparency can be further defined quantitatively, where appropriate, by measuring specular light transmission. This measurement consists of measuring the light intensity along the axis of the incident light ray. A material can be considered transparent when its specular light transmission is greater than or equal to 30%, preferably greater than 40%, or greater than 50%, or greater than 60%.

[0057] Unlike opaque materials of which only the surface is optically active, the transparent nature of the material according to the invention makes it possible to obtain a volume effect, namely a multiplying effect of the optical properties.

[0058] Thus, advantageously, the entire volume of said material is optically active.

[0059] The term “optically active material” means a material that exhibits persistent luminescence properties, that is to say, a material capable of emitting light after being exposed to a light source and after that source has been removed.

[0060] Advantageously, said material is out of thermodynamic equilibrium.

[0061] By "non-thermodynamic equilibrium" we mean that the material is metastable, that is to say, it is able to switch to a more stable structural state under the effect of an energy input (for example, by heating). Indeed, the material according to the invention has the capacity to change its structure at high temperatures below its melting point.

[0062] Advantageously, the material according to the invention is a mechanoluminescent material.

[0063] Indeed, in addition to persistent luminescence properties, the material according to the invention has the advantage of also exhibiting mechanoluminescence properties.

[0064] Mechanoluminescence refers to the property of a material to emit light after being exposed to mechanical stress and after that mechanical stress has been removed.

[0065] Thus, a "mechanoluminescent material" is understood to be a material capable of emitting light under the effect of mechanical stress.

[0066] According to one embodiment, the material is in the form of a solid material, such as a solid glass-ceramic.

[0067] According to another embodiment, the material is in the form of a powder.

[0068] The present invention also relates to a method for manufacturing the material according to the invention comprising the following steps:

[0069] a) supply of a precursor mixture comprising at least: - a strontium precursor, an aluminium precursor, a silica precursor, - optionally a precursor of X, - optionally a precursor of X', - optionally a precursor to RE, - optionally a precursor of Y, - optionally a precursor to Z, - optionally a precursor of M,

[0070] according to the molar ratio of said material as defined in one of the formulas (I), (II), (la), (lia),

[0071] b) melting of the precursor mixture at a temperature greater than or equal to 1500°C, preferably between 1600 and 1800°C, more preferably between 1650 and 1700°C;

[0072] c) solidification of the molten mixture by cooling and obtaining a glass;

[0073] d) crystallization of the glass obtained in step c), at a temperature greater than or equal to at 900°C, preferably between 900°C and 1300°C, more preferably between 900°C and 1200°C.

[0074] Advantageously, the crystallization is congruent.

[0075] For the purposes of this invention, "congruent crystallization" means crystallization in which the chemical composition of the material obtained by the process of the invention is identical to that of the glass from which it is derived.

[0076] Advantageously, during step c), solidification is obtained by rapid cooling, i.e. by cooling for a period of less than 5 min, preferably less than 1 min.

[0077] The invention also relates to an article comprising the material as defined above.

[0078] Thanks to the remarkable properties of the material according to the invention, it has the advantage of being able to be used in different fields as well as for various applications.

[0079] By way of illustration, the material according to the invention can be used for decorative purposes in the fields of fashion, toys, paints, and inks. The material according to the invention can also be used in the fields of jewelry, optics, security, and signage.

[0080] Thus, the invention also relates to the use of the material as defined above for the manufacture of an optical material, a piece of jewelry or a signage element.

[0081] The term "signage element" means any visual or textual element used to identify or orient in a given space. This element may include signs, nameplates, information kiosks, labels, posters, pictograms, etc.

[0082] Other advantages may become apparent to those skilled in the art upon reading the examples below, illustrated by the accompanying figures, which are given for illustrative purposes. BRIEF DESCRIPTION OF THE FIGURES

[0083] - [Fig. 1] [Fig. 1] represents the ray diffraction patterns X-ray (XRD) of the material with the formula Sr^A^oSi^Oee measured using CuKal,2 radiation at a Bragg angle of 20, after the quenching step in its glassy state (left figure), and after the annealing / crystallizing step in its crystalline state (right figure). - [Fig.2] Fig.2 represents the crystal structure diagrams of the Sr^Al^Si^Ogg material, viewed along the a and c axes of the crystallographic unit cell (hexagonal, space group P63).

[0084] Example 1: Synthesis of a material of formula Sr n Al Si n O

[0085] This material is prepared by melting the raw materials that make up its composition, resulting in a high-temperature molten liquid, followed by solidification of this molten liquid by rapid cooling to room temperature and then a second crystallization step by thermal annealing. The process is detailed below.

[0086] High-purity precursors, strontium carbonate (SrCO3 99.999% Strem), alumina (Al2O3 99.99% Alfa Aesar), and silica (SiO2 99.999% Strem), were first dried and then weighed according to the desired molar ratio, Sr^AboSinOee. This mixture of precursors was then finely ground and mixed in an agate mortar, then placed in a platinum crucible and heated to 1650°C in a muffle furnace. Once melted, the sample was maintained at this temperature for 1 hour and 30 minutes. To ensure thorough homogenization, the mixture was cooled to room temperature in approximately one minute by placing the platinum crucible in cold water. The resulting glass was then finely ground and pelletized by uniaxial pressing (~50 mg, 5 mm diameter, 1 mm thickness). The pellets were then returned to the platinum crucible and crystallized by heat treatment at 1150°C for one hour.

[0087] Example 2: Synthesis of a material with the formula Sr, 176Eu0 i2Dy0 i2A12oSi6066

[0088] The same technique was used, except that 1 mole percent of europium oxide (Eu2O3 99.999% Strem) and 1 mole percent of dysprosium oxide (Dy2O3 99.999% Strem) were substituted for strontium carbonate, giving Srii.76Euo.i2Dyo.i2Al2oSi6066, and the crystallization step was carried out in a tubular furnace under a nitrogen atmosphere. Example 3: Example of synthesized materials

[0089] Other materials according to the invention have been synthesized.

[0090] Tables 1 and 2 below list examples of materials obtained by implementing the processes described in Example 1 or 2.

[0091] [Tables 1] Materials according to formula (I) Srio.8Ba12Al2oSii2066 SrçgB a2.4 Al2oSi 12Oee Sr8 4B a3.6 Al20Si i 20g6 Srio.8Cai.2Al2oSii2066 SrQ.6Ca2.4 Al20Si 12OM) Sr8.4Ca36Al2oSi2066 Sr 11. ve Eu012Dy o. 12A11 oSig033 Sr 11 44 ​​Eu012Dy o.^Al! 0SigO33

[0092] [Tables2] Materials according to formula (II) Sri23Al2o.6Siii,4066 Sri2.6Al2i.2Siio.8066 Sri2.gAl2i.8Sii0.2O66

Claims

Demands

1. Ceramic or glass-ceramic material meeting one of the following formulas: [(Sri_abbi XaiX'bi)i.e REe]i2+c [(Ali_dYd)i_fMf]20+2c[(Sii-gZg)i_hMh]i2-2cO66 formula (I) [(Sr12-a2-b2 Xj2X'b2)! formula (II) in which: - X represents at least one alkaline earth metal other than barium, - X' represents at least one alkaline earth metal, - RE represents at least one element chosen from the group consisting of rare earths, bismuth (Bi) and one of their combinations, - Y represents at least one element chosen from the group consisting of metalloids, post-earth metals, non-metals and one of their combinations, - M represents at least one transition metal, - Z represents at least one element chosen from the group consisting of metalloids, non-metals and one of their combinations, 0 < al < 1 0 <bl<l / 3 - 0< a2<12 0< b2<12 0<c<l 0<d<l - e, f, g et h sont supérieurs ou égaux à zéro et strictement inférieur à 1.

2. Material according to claim 1 characterized in that X represents calcium.

3. Material according to claim 1 characterized in that X' represents barium.

4. Material according to any one of the preceding claims, characterized in that Y represents gallium and / or boron.

5. Material according to any one of the preceding claims, characterized in that Z represents germanium.

6. Material according to any one of the preceding claims, characterized in that RE is chosen from the group consisting of Eu, Gd, Ce, Ho, Yb, Dy, Pr, Nd, Tb, Er, Tm, Bi and one of their combinations.

7. Material according to any one of the preceding claims, characterized in that M is chosen from the group consisting of Ti, Cr, Mn, Fe, Co, Ni, Cu and one of their combinations.

8. Material according to any one of the preceding claims, characterized in that said material conforms to one of the following formulas: [(Srl al bl CaalBabl)le REe]12+c [(AlldiGad Bi)1_fMf]20+2c[(Sii_gGeg)1_ hMh] 12 2cOb6 formula (la) [(Sr12 a2 b2 Caa2Bab2)ie REe][(AlldiGadBi)1_fMf]2o[(Sii_gZg)lhMh]12066 formula (la) in which: 0 <i<l - al,a2, bl, b2, c, d, e, f, g, h, Z, RE et M sont tels que définis à la revendication 1.

9. Material according to claim 1 or 8, characterized in that said material corresponding to formula (I) or formula (la) is chosen from the following materials: — Sri2+cAl20+2cSii2_2cO66 — Sri2CacAl2o+2cSii2_2cO66 — Sri2BacAl2o+2cSii2_2cO66 with 0 < c < 1, preferably c is between 0.3 and 0.

9.

10. Material according to claim 1 or 8, characterized in that said material corresponding to formula (II) or to formula (lia) is selected from the following materials: - Sri2 b2Bab2Al20Sii2O66 with 0 < b2 < 12, preferably b2 is between 1.2 and 3.6; - Sri2 a2Caa2Al2oSii2O66 with 0 < a2 < 12, preferably a2 is between 1.2 and 3.6; - Sri2 eREeAl20Sii2O66 with RE representing Eu and / or Dy and with 0 < e < 1, preferably e is between 0.12 and 0.

24.

11.

12.

13.

14.

15.

16. Material according to any one of the preceding claims, characterized in that it corresponds to the formula Sri2Al20Sii2O66. Material according to any one of the preceding claims, characterized in that it is transparent. Material according to any one of claims 1 to 8, 10 or 12, characterized in that when e is greater than zero, said material exhibits persistent luminescence. A method for manufacturing the material according to any one of claims 1 to 13, comprising the following steps: a) supply of a precursor mixture comprising at least: - a strontium precursor, an aluminium precursor, a silica precursor, - optionally a precursor of X, - optionally a precursor of X', - optionally a precursor to RE, - optionally a precursor of Y, - optionally a precursor to Z, - optionally a precursor of M, according to the molar ratio of said material as defined in claims 1 to 13, b) melting of the precursor mixture at a temperature greater than or equal to 1500°C, c) solidification of the molten mixture by cooling and obtaining a glass, d) crystallization of the glass obtained in step c), at a temperature greater than or equal to 900°C. A process according to claim 14, wherein the crystallization is congruent. Use of the material as defined in claims 1 to 13, for the manufacture of an optical material, a piece of jewelry or a signage element.

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