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 formulae: [(Sr1-a1-b1 Xa1X'b1)1-eREe] 12+c[(Al1-dYd)1-f Mf] 20+2c [(Si1-gZg)1-hMh]12-2cO66 formula (I) [(Sr12-a2-b2Xa2X'b2)1-eREe][(Al1-dYd)1-fMf]20[(Si1-gZg)1-hMh]12O66 formula (II) wherein: - X represents at least one alkaline-earth metal with the exception of 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 the combinations thereof; - Y represents at least one element selected from the group consisting of metalloids, post-transition metals, non-metals, and one of the combinations thereof; - M represents at least one transition metal; - Z represents at least one element selected from the group consisting of metalloids, non-metals and one of the combinations thereof; - 0 ≤ a1 ≤ 1 - 0 ≤ b1 ≤ 1 / 3 - 0 ≤ a2 ≤ 12 - 0 ≤ b2 < 12 - 0 ≤ c < 1 - 0 ≤ d < 1 - e, f, g and h are greater than or equal to zero and strictly less than 1.

Description

[0001] Description

[0002] Title: Persistent Luminescence Ceramic or Glass-Ceramic Material

[0003] TECHNICAL FIELD OF THE INVENTION

[0004] 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, especially persistent luminescence.

[0005] DESCRIPTION OF THE INVENTION

[0006] Persistent luminescence refers to the ability of certain materials to continue emitting light after being exposed to a light source and then removed. These materials thus have the capacity to absorb a certain amount of energy, which they then release as light for periods of up to several hours.

[0007] Because of their ability to emit light for an extended period after exposure to a light source (UV, sunlight, etc.), these materials have applications in diverse fields such as signage, security, optical devices, biomedical imaging, jewelry, and more. However, despite strong demand, very few materials currently exhibit these properties. Furthermore, the range of emitted colors is currently very limited.

[0008] The most commonly used persistent luminescence materials are:

[0009] Europium- and dysprosium-doped strontium aluminate (SrA₂C) is the best-known commercial material (with various applications, notably in security, jewelry / aesthetics). It emits in the green range (a non-modulatable greenish color).

[0010] Europium-doped calcium aluminate CaAhC emits in the blue.

[0011] The compound CaS emits in the red, however, it is not chemically stable.

[0012] However, these materials are not transparent. Yet transparency is a necessary parameter for certain applications, particularly 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 suffers from high rejection rates. Consequently, there is a real need for persistent luminescence materials that are both transparent and fully active, exhibit new emission colors, and can be used for a variety of applications.

[0013] The present invention relates first to a ceramic or glass-ceramic material conforming to one of the following formulas:

[0014] [(Sr-|-al-bl XaiX'bl)le RE e ] 12+c [(Ah -dYd) 1 -f Mf] 20+20 [(Sh -gZg) 1 -h Mh ] 12-2C 066 formula (I)

[0015] [(Sri2-a2-b2 Xa2X'b2)the RE e ] [(Al 1 -dYd) 1 -f Mf] 20 [(Sil -gZg) 1 -h Mh ] 12 066 formula ( II) in which:

[0016] X represents at least one alkaline earth metal, excluding barium.

[0017] - X' represents at least one alkaline earth metal,

[0018] RE represents at least one element chosen from the group consisting of rare earth elements, bismuth (Bi) and one of their combinations,

[0019] - Y represents at least one element chosen from the group consisting of metalloids, post-metals, non-metals and one of their combinations,

[0020] - M represents at least one transition metal,

[0021] - Z represents at least one element chosen from the group consisting of metalloids, non-metals, and one of their combinations,

[0022] - 0 < a1 < 1

[0023] - 0 < b1 < 1 / 3

[0024] - 0 < a2 < 12

[0025] - 0 < b2 < 12

[0026] - 0 < c < 1

[0027] - 0 < d < 1

[0028] - e, f, g and h are greater than or equal to zero and strictly less than 1.

[0029] 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.

[0030] For the purposes of this invention, "glass-ceramic" 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. It should be noted that, for the purposes of this application, and unless otherwise stipulated, the ranges of values ​​indicated include the limits.

[0031] The material according to the invention is a strontium aluminosilicate whose composition can be modified by substituons and / or dopants.

[0032] Thus, strontium can be substituted by X and / or X'.

[0033] Advantageously, X represents at least one alkaline earth metal chosen from the group consisting of Mg and Ca. Preferably, X represents calcium (Ca).

[0034] Advantageously, X' represents at least one alkaline earth metal chosen from the group consisting of Mg, Ba and Ca. Preferably X represents barium (Ba).

[0035] Advantageously, the values ​​of a1 and b1 in the material of formula (I) are such that a1 +b1 <1.

[0036] Advantageously, the values ​​of a2 and b2 in the material of formula (II) are such that a2+b2<12.

[0037] Aluminium can be substituted by the variable Y as defined previously in formulas (I) or (II).

[0038] 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.

[0039] Advantageously, the metalloids are chosen from the group consisting of: B, Si, Ge, As, Sb. Preferably B (boron).

[0040] Advantageously, the low-grade metals are chosen from the group consisting of Zn, Ga, In and Sn. Preferably Ga (gallium).

[0041] Advantageously, the non-metals are chosen from the group consisting of phosphorus (P) and sulfur (S). Preferably P (phosphorus).

[0042] Advantageously, Y represents gallium and / or boron.

[0043] Silica can be substituted by Z.

[0044] 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.

[0045] Advantageously, the metalloids are chosen from the group consisting of B, Ge, As, Sb, Te. Preferably Ge (germanium).

[0046] Advantageously, the non-metals are chosen from the group consisting of phosphorus (P), sulfur (S), and selenium (Se). Preferably phosphorus (P).

[0047] Advantageously, Z represents germanium (Ge). Advantageously, the material according to the invention is doped with dopants selected from the group consisting of rare earths, transition metals, bismuth (Bi) and a combination thereof.

[0048] 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, such as luminescence. In particular, when doped, the material according to the invention exhibits persistent luminescence by emitting a blue color.

[0049] Advantageously, rare earth elements 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.

[0050] Advantageously, RE is chosen from the group consisting of Eu, Dy, Bi and one of their combinations.

[0051] Advantageously, when in formula (I) or (II) the number e is greater than zero, said material exhibits persistent luminescence.

[0052] 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%.

[0053] Advantageously, M represents at least one transition metal chosen from the group consisting of Ti, Cr, Mn, Fe, Co, Ni, Cu and one of their combinations. Preferably, M represents Cr (chromium).

[0054] Transition metal doping allows the introduction or improvement of the material's optical properties, such as emission color and persistent luminescence lifetime.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] Advantageously, said material corresponds to one of the following formulas: [(Sri- a i-bi Ca a iBabi)i- e D e ] i2+c [(Ah-d iGad Bi)if Mf] 20+20 [(Sii- g Ge g)ih Mh ] 12-20 O&& formula (the)

[0059] [(Sri2 a2-b2 Ca a 2Bab2)ie RE e ] [(Ah-d GadBi)i .f Mf] 20 [(Sii - g Z g )i -h Mh ] 12 0&& formula (Ila) in which:

[0060] - 0 < i < 1

[0061] - a1, a2, b1, b2, c, d, e, f, g, h, Z, RE and M are as defined previously.

[0062] Advantageously, said material corresponding to formula (I) or formula (la) is chosen from among the following materials:

[0063] Sri 2+cAl20+2cSi 12-2cO66

[0064] Sri2Ca c Al2O+2cSi2-2cO66

[0065] Sri2Ba c Al20+2cSii2-2cO66 with 0 < c < 1, preferably c is between 0.3 and 0.9.

[0066] Advantageously, said material corresponding to formula (II) or formula (lia) is chosen from the following materials:

[0067] Sri2 b2Bab2Al2oSii2C>66 with 0< b2<12, preferably b2 is between 1.2 and 3.6;

[0068] Sri2- a 2Ca a 2Al2oSii2066 with 0< a2<12, preferably a2 is between 1.2 and 3.6;

[0069] - Sri2- e D e Al2oSii2066 with RE representing Eu and / or Dy and with 0 < e < 1, preferably e is between 0.12 and 0.24.

[0070] Advantageously, said material corresponds to the formula Sr^AhoSi^Oee ■

[0071] Advantageously, the material according to the invention is transparent.

[0072] For the purposes of this invention, "transparent" means that the material can be seen through it (within the visible spectrum). This qualitative notion of transparency can be further defined quantitatively, if necessary, 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%. Unlike opaque materials, of which only the surface is optically active, the transparency of the material according to the invention creates a volume effect, namely a multiplication effect of the optical properties. Thus, advantageously, the entire volume of the material is optically active.

[0073] An "optically active material" is defined as a material that exhibits persistent luminescence properties, that is, a material capable of emitting light after being exposed to a light source and after that source has been removed.

[0074] Advantageously, the said material is out of thermodynamic equilibrium.

[0075] By "non-thermodynamic equilibrium," we mean that the material is metastable, that is, it is capable of shifting to a more stable structural state under the influence of 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.

[0076] Advantageously, the material according to the invention is a mechanoluminescent material.

[0077] Indeed, in addition to persistent luminescence properties, the material according to the invention has the advantage of also exhibiting mechanoluminescence properties.

[0078] 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.

[0079] Thus, a "mechanoluminescent material" is understood to be a material capable of emitting light under the effect of mechanical stress.

[0080] According to one embodiment, the material is in the form of a solid material, such as a solid glass-ceramic.

[0081] According to another embodiment, the material is in the form of a powder.

[0082] The present invention also relates to a method for manufacturing the material according to the invention comprising the following steps: a) supplying a mixture of precursors 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 of RE, optionally a precursor of Y,

[0083] - optionally a precursor of Z, optionally a precursor of M, according to the molar ratio of said material as defined in one of the formulas (I),

[0084] (II), (la), (lia), 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; 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, preferably between 900°C and 1300°C, more preferably between 900°C and 1200°C.

[0085] Advantageously, the crystallization is congruent.

[0086] 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.

[0087] Advantageously, in step c), solidification is achieved by rapid cooling, i.e. by cooling for a period of less than 5 min, preferably less than 1 min.

[0088] The invention also relates to an article comprising the material as defined above.

[0089] 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 varied applications.

[0090] 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.

[0091] 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.

[0092] The term "signage element" refers to any visual or textual element used to identify or guide people within a given space. This element may include traffic signs, nameplates, information kiosks, labels, posters, pictograms, etc.

[0093] Other advantages may also become apparent to the person skilled in the art upon reading the examples below, illustrated by the attached figures, given for illustrative purposes.

[0094] BRIEF DESCRIPTION OF THE FIGURES

[0095] - [Fig.1 ] Figure 1 represents the X-ray diffraction (XRD) diagrams of the material with the formula Sr^AhoSi^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).

[0096] - [Fig. 2] Figure 2 represents the diagrams of the crystal structure of the material Sr^ALoSi^Oee, seen along the a and c axes of the crystallographic unit cell (hexagonal, space group P6s).

[0097] [Fig. 3] Figure 3 shows a photograph of the material of the invention taken in ambient light. This photograph illustrates the transparency of a sample of Sri2AI2oSii2066 material placed on a printed pattern.

[0098] [Fig. 4] Figure 4 represents the CIE 1931 chromaticity of the emission from the Sri2Al2oSii2O66 material. The measured point, represented by a star-shaped marker, is located at (x = [0.17]; y = [0.17]). This position lies within the region corresponding to the short wavelengths of the spectral locus (portion 460-480 nm), which confirms a blue-centered emission.

[0099] [Fig. 5] Figure 5 represents the normalized emission intensity decay curve (logarithmic scale) of the B-Sri2Al2oSii2066:Eu material 2+ ,Dy 3+ , depending on the time after interruption of the excitation. The black line represents the normalized baseline (instrument noise / sensitivity).

[0100] Example 1: Synthesis of a material with the formula

[0101] This material is prepared by melting the raw materials that make up its composition, resulting in a high-temperature molten liquid. This is followed by solidification of the molten liquid through rapid cooling to room temperature, and then a second crystallization stage by thermal annealing. The process is detailed below.

[0102] 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, Sr²⁺²⁰Si²⁺²⁰⁻. This precursor mixture was then finely ground and blended in an agate mortar, then placed in a platinum crucible and heated to 1650°C in a muffle furnace. Once melted, the sample was held at this temperature for 1 hour and 30 minutes to ensure thorough homogenization before being cooled to room temperature in approximately one minute by placing the platinum crucible in cold water. The resulting glass was then further finely ground and pelletized by uniaxial pressing (~50 mg, 5 mm diameter, 1 mm thickness). The pellets obtained were placed back in the platinum crucible and crystallized by heat treatment at 1150°C for 1 hour.

[0103] Example 2: Synthesis of a material with the formula Srn yeEuo ^Dvo ^AhoSieOee

[0104] 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 Srn.yeEuo.^Dyo.^AhoSieOee, and the crystallization step was carried out in a tubular furnace under a nitrogen atmosphere.

[0105] Example 3: Example of synthesized materials

[0106] Other materials according to the invention have been synthesized.

[0107] Tables 1 and 2 below list examples of materials obtained by implementing the processes described in example 1 or 2.

[0108] [Table 1]

[0109] [Table 2]

[0110] Example 4: Characteristics of the formula material Figures 3 to 5 demonstrate that the Sri2AI2oSii2066 material meets the required optical criteria, namely:

[0111] (i) The photograph of the printed pattern shows macroscopic transparency of the Sri2AI2oSii2066 pellet, without any visible haze or defects, any distortion of the letters resulting only from a slight lens effect; (ii) the PerL decay curve of B-Sri2AI2oSii2066:Eu 2+ ,Dy 3+ highlights a persistent, long-lasting luminescence, extending over several hours after extinction, with long-tailed kinetics consistent with a trapping / untrapping mechanism;

[0112] (iii) the CIE 1931 diagram places the emission chromaticity in the blue-violet zone (close to the 460-480 nm segment of the spectral locus), confirming an emission centered in the blue.

[0113] All of these results confirm that it is a transparent material exhibiting blue emission and persistent luminescence.

Claims

Demands 1. Ceramic or glass-ceramic material meeting one of the following criteria: [(Sr-|-al-bl XaiX'bl)le RE e ] 12+c [(Ah -dYd) 1 -f Mf] 20+20 [(Sh -gZg) 1 -h Mh ] 12-2C 066 formula (I) [(Sri2 a2-b2 Xa2X'b2)ie RE e ] [(Al 1 -dYd) 1 f Mf] 20 [(Sii -gZg) 1 -h Mh ] 120&& 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 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-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 < 1 - 0 < b1 < 1 / 3 - 0 < a2 < 12 - 0 < b2 < 12 - 0 < c < 1 - 0 < d < 1 - e, f, g and h are greater than or equal to zero and strictly less than 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: [(Sri- a i-bi Ca a iBabi)i- e D e ] i2+c [(Ah-d iGad Bi)if Mf] 20+20 [(Sii- g Ge g )ih Mh ] 12-20 Oee formula (the) [(Sri2 a2-b2 Ca a 2Bab2)i- e D e ] [(Ah-d adBi)i .f Mf] 20 [(Sii - g Z g )i -h Mh ] 12 O&& formula (lia) in which: - 0 < i < 1 - a1, a2, b1, b2, c, d, e, f, g, h, Z, RE and M are as defined in claim 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: Sri 2+cAl20+2cSi 12-2cO66 Sri2Ca c Al2O+2cSi2-2cO66 Sri2Ba c Al20+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 formula (lia) is selected from the following materials: Sri2 b2Bab2Al2oSii2066 with 0< b2<12, preferably b2 is between 1.2 and 3.6; Sri2- a 2Ca a 2Al2oSii2066 with 0< a2<12, preferably a2 is between 1.2 and 3.6; - Sri2- e D eAl2oSii2066 with RE representing Eu and / or Dy and with 0 < e < 1, preferably e is between 0.12 and 0.

24.

11. Material according to any one of the preceding claims, characterized in that it conforms to the formula Sri2Al2oSii2O66 ■ 12. Material according to any one of the preceding claims, characterized in that it is transparent.

13. 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.

14. A method for manufacturing the material according to any one of claims 1 to 13, comprising the following steps: a) supplying a mixture of precursors 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 of RE, optionally a precursor of Y, - optionally a precursor of 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 mixture of precursors 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.

15. A method according to claim 14, wherein the crystallization is congruent.

16. 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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