A high crystallinity transparent glass-ceramic material containing a multi-scale twin phase

Abstract

This invention discloses a highly crystalline transparent glass-ceramic material containing a multi-scale bicrystalline phase. The glass-ceramic material has the formula 20BaO-20Al2O3-20LaF3-40SiO2-xTbF3. LaF3 nanocrystals and BaAl2Si2O8 microcrystals are precipitated in the glass-ceramic material, forming a multi-scale bicrystalline phase structure. Tb is doped in the form of TbF3 in the glass-ceramic material. 3+ Tb 3+ The doping concentration x is 0 < x ≤ 26 mol%, and the doped Tb 3+ Partially replacing La in LaF3 nanocrystals 3+ Lattice sites and Ba in BaAl2Si2O8 micron-sized crystals 2+ This glass-ceramic material possesses high crystallinity, high transmittance, and strong scintillation luminescence properties; within a temperature range of 303–523 K, its luminescence intensity exhibits resistance to thermal quenching and reversible thermal recovery properties; when applied to X-ray imaging, it shows great potential in the field of static X-ray imaging.

Description

Technical Field

[0001] This invention belongs to the field of glass ceramics technology, specifically relating to a highly crystalline transparent glass ceramic material containing multi-scale bicrystalline phases. Background Technology

[0002] Scintillators, as core functional materials in the field of radiation detection technology, can convert X-rays, gamma rays, or high-energy particles into detectable ultraviolet-visible light signals, demonstrating significant application value in high-energy physics experiments, nuclear medicine imaging, industrial non-destructive testing, security inspection, environmental monitoring, and astronomical observation. With the increasing demands for detection accuracy and environmental adaptability in these applications, the development of novel scintillator materials with high light output, excellent energy resolution, and strong radiation resistance has become a current research hotspot.

[0003] Compared to traditional single-crystal scintillators, rare-earth ion-doped glass scintillators have advantages such as high doping concentration, large-size fabrication and easy molding, and low cost. However, the disordered structure of the glass and the high phonon energy result in low luminous efficiency, which limits its light yield and energy resolution.

[0004] Glass-ceramics are composite optical materials composed of a glassy phase and a crystalline phase. They combine the excellent processability of glass with the efficient luminescence properties of crystals, attracting widespread attention in the field of light conversion. In particular, glass-ceramics with a high phase-to-volume ratio have garnered significant attention due to their unique structural advantages: on the one hand, the crystalline phase provides an ordered crystal field environment with low phonon energy for luminescent centers (such as rare-earth ions), significantly reducing the probability of nonradiative transitions and improving luminescence efficiency; on the other hand, higher crystallinity reduces the defect concentration in the amorphous matrix phase, thereby improving the stability of the glass-ceramic. These properties give high phase-to-volume ratio glass-ceramics great potential for optimizing scintillator performance; therefore, developing glass-ceramics with a high phase-to-volume ratio has significant scientific value and application prospects.

[0005] However, glass-ceramics with high phase-to-volume ratios often face a trade-off between crystallinity and optical transparency: when grain size is controlled to be much smaller than the visible light wavelength (<400nm) to reduce light scattering, crystallinity is often difficult to improve (due to an excessively high proportion of glass phase); conversely, to achieve high crystallinity, precise matching of the refractive indices of the crystalline and glass phases is required, along with continuous and uniform evolution of the components during crystallization (e.g., through phase separation crystallization mechanisms). This requirement imposes stringent control requirements on the crystalline phase composition, grain size distribution, and spatial distribution of the glass system. Therefore, it is urgent to obtain novel glass-ceramic materials with high crystallinity, high transparency, and excellent luminescence performance through rational design of the component system and synergistic optimization of the preparation process, providing technical support for the development of high-efficiency scintillator light conversion materials. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a highly crystalline transparent glass-ceramic material containing a multi-scale bicrystalline phase. This glass-ceramic material contains a multi-scale bicrystalline phase structure formed by LaF3 nanocrystals and BaAl2Si2O8 microcrystals, and is doped with luminescent ions Tb. 3+ Through multi-scale bicrystalline phase synergistic design, a balance between high crystallinity (≥80%) and high transmittance (≥70% transmittance at 543nm wavelength) was achieved, and the scintillation luminescence performance of glass-ceramic materials was significantly improved.

[0007] The technical solution adopted by this invention to solve the above-mentioned technical problems is as follows: a highly crystalline transparent glass-ceramic material containing a multi-scale bicrystalline phase, the glass-ceramic material having the composition formula 20BaO-20Al2O3-20LaF3-40SiO2-xTbF3, wherein LaF3 nanocrystals and BaAl2Si2O8 microcrystals are precipitated in the glass-ceramic material, the LaF3 nanocrystals and BaAl2Si2O8 microcrystals forming a multi-scale bicrystalline phase structure, and Tb is doped in the form of TbF3 in the glass-ceramic material. 3 + Tb 3+ The doping concentration x is 0 < x ≤ 26 mol%, and the doped Tb 3+ Partially replacing La in the LaF3 nanocrystals 3+ Lattice sites and Ba in the BaAl2Si2O8 micron crystal 2+ Grid position.

[0008] The glass-ceramic material of this invention contains a multi-scale bicrystalline phase structure formed by LaF3 nanocrystals and BaAl2Si2O8 microcrystals, and is doped with luminescent ions Tb. 3+ By regulating Tb 3+ The doping amount can not only regulate the emission of Tb ions 3+ The luminescence intensity significantly improves the scintillation luminescence performance of glass-ceramic materials and can also induce the transformation of BaAl2Si2O8 micron crystals from monoclinic to hexagonal phase.

[0009] Tb doped in the glass-ceramic material of this invention 3+ By preferentially occupying La in LaF3 nanocrystals 3+ Lattice sites and BaAl2Si2O8 micron-sized Ba 2+ The lattice sites form a dual-luminescent-center system. Specifically, the LaF3 nanocrystals provide a low-phonon energy environment, enabling... 5 D4→ 7 F JThe fluorescence enhancement of the (J=6,5,4,3) transitions simultaneously promotes the precipitation of second-phase BaAl2Si2O8 micron-sized crystals; the multi-scale structure constructed by the precipitation of BaAl2Si2O8 micron-sized crystals can improve the utilization rate of incident light and further enhance the luminescence intensity. Specifically, the La in the precipitated LaF3 nanocrystals... 3+ The radius (r = 0.103 nm) and the luminescent ion Tb 3+ The radii (r = 0.092 nm) are similar, and their valence states are matched, therefore the incorporated Tb... 3+ It can be preferentially embedded into LaF3 nanocrystals with low phonon energy, replacing the La in the LaF3 nanocrystals. 3+ Grid, to achieve Tb 3+ Enhanced green light emission; furthermore, due to Ba 2+ The radius (r = 0.135 nm) is also greater than Tb. 3+ radius, small amount of Tb 3+ It can be embedded in the lattice of BaAl2Si2O8 micron-sized crystals and partially replace Ba. 2 + The substitution mechanism of the lattice can be described as Ba 2+ Charge compensation process at lattice sites: three Ba2 + The cell was occupied by two Tb 3 + occupies, forming two cation defects and one anion vacancy. Therefore, part of Tb 3+ It can also be placed in an ordered crystal field provided by a BaAl2Si2O8 micron crystal, which promotes green emission.

[0010] In this invention, the precipitated LaF3 nanocrystals and BaAl2Si2O8 microcrystals in the glass-ceramic material form a multi-scale bicrystalline phase structure. The precipitation of LaF3 nanocrystals alters the local chemical structure of the glass, lowers the crystallization barrier, and promotes the precipitation of BaAl2Si2O8 microcrystals. The low refractive index difference between the LaF3 and BaAl2Si2O8 microcrystals and the glass phase ultimately results in a transparent glass-ceramic material. The precipitation of these two crystals, LaF3 and BaAl2Si2O8, not only improves the overall crystallinity but also constructs a multi-scale structure within the glass, allowing incident light to be fully absorbed and converted, thereby further enhancing the luminescence intensity and providing a source of Tb luminescent ions. 3+ Provide a suitable light-emitting environment.

[0011] Furthermore, by changing Tb 3+The doping concentration not only affects the luminescence intensity but also induces a phase transition in BaAl₂Si₂O₈ microcrystals. Monoclinic BaAl₂Si₂O₈ crystals, also known as barium feldspar crystals, are widely found in nature, while hexagonal BaAl₂Si₂O₈ crystals are rarer and typically require high temperature and pressure conditions in the laboratory for synthesis. This invention, by changing the TbF₃ content, can control the transformation of precipitated BaAl₂Si₂O₈ microcrystals from monoclinic to hexagonal phase. This hexagonal BaAl₂Si₂O₈ microcrystal is beneficial for improving the transparency of glass-ceramic materials. Specifically, LaF₃ nanocrystals significantly reduce Rayleigh scattering through their size effect (much smaller than the visible light wavelength), while the hexagonal BaAl₂Si₂O₈ microcrystal, due to its relatively symmetrical lattice structure and its refractive index matching with the glass phase, forms a low-scattering-loss composite structure, thereby improving the transmittance of the glass-ceramic material and achieving a balance between high crystallinity and high transparency. The crystallinity is ≥80%, and the transmittance at 543 nm wavelength is ≥70%.

[0012] Tb is preferred in the glass-ceramic material of this invention. 3+ The doping concentration x is 2 ≤ x ≤ 26 mol%. Specifically, Tb 3+ When the doping concentration is low, LaF3 nanocrystals and monoclinic BaAl2Si2O8 microcrystals precipitate inside the glass-ceramic material. For example, Tb 3+ When the doping concentration is 2 mol%, LaF3 nanocrystals and monoclinic BaAl2Si2O8 micron-sized crystals precipitate in the glass-ceramic material of this invention. At this point, the transmittance of the glass-ceramic material of this invention is low, approximately 53%, and the haze is severe. When Tb 3+ When the doping concentration is high, LaF3 nanocrystals and hexagonal BaAl2Si2O8 microcrystals precipitate inside the glass-ceramic material of this invention. For example, Tb 3+ When the doping concentration is 22 mol%, LaF3 nanocrystals and hexagonal BaAl2Si2O8 microcrystals are precipitated in the glass-ceramic material of the present invention. At this time, the transmittance of the glass-ceramic material of the present invention is significantly improved, and its transmittance at a wavelength of 543 nm is ≥70%.

[0013] In the glass-ceramic material of this invention, the average size of the LaF3 nanocrystals is 30–60 nm, and the average size of the BaAl2Si2O8 microcrystals is 50–70 μm. This multi-scale structure of different sizes of the LaF3 nanocrystals and BaAl2Si2O8 microcrystals ensures the synergistic optimization of high crystallinity and excellent optical transparency in the glass-ceramic material of this invention.

[0014] In the glass-ceramic material of the present invention, the LaF3 nanocrystals are hexagonal LaF3 crystal phases, and the BaAl2Si2O8 micron crystals are monoclinic BaAl2Si2O8 crystal phases and / or hexagonal BaAl2Si2O8 crystal phases.

[0015] Tb 3+ When the doping concentration x is 22 mol%, the crystallinity of the glass-ceramic material is 80-85%, the transmittance of the glass-ceramic material at a wavelength of 543 nm is ≥70%, and the BaAl2Si2O8 micron crystal is a hexagonal BaAl2Si2O8 crystal phase.

[0016] The glass-ceramic material of the present invention utilizes Tb 3+ The strong shielding effect of the 4f orbital makes it difficult for temperature changes to significantly affect its energy level structure, thus ensuring Tb 3+ The energy level is stable at different temperatures. Partial Tb is present during crystallization. 3+ Electrons and holes enter the crystal lattice and replace corresponding lattice sites, disrupting lattice symmetry and vibrational modes, thus forming trap defects. By modulating the transport and recombination behavior of electrons and holes, the glass-ceramic material of this invention exhibits anomalous thermally enhanced luminescence in the temperature range of 303–523 K, resulting in a glass-ceramic material with resistance to thermal quenching and excellent thermal recovery properties. Within the temperature range of 303–523 K, the luminescence intensity of the glass-ceramic material exhibits resistance to thermal quenching and reversible thermal recovery properties.

[0017] The glass-ceramic material of this invention possesses high density and atomic number, which is beneficial for increasing the absorption cross-section for high-energy rays or ions. X-ray excitation luminescence (XEL) tests show that the combined effect of high crystallinity and high density enables the luminescence intensity of the glass-ceramic material of this invention to reach 202% (integral intensity ratio) of commercial BGO crystals. When applied to X-ray imaging, the glass-ceramic material of this invention has great potential in the field of static X-ray imaging due to its spatial resolution of 16 LP / mm.

[0018] Compared with the prior art, the present invention has the following advantages: the glass-ceramic material of the present invention contains a multi-scale bicrystalline phase structure formed by LaF3 nanocrystals and BaAl2Si2O8 microcrystals, and is doped with luminescent ions Tb. 3+ By regulating Tb 3+ The doping amount can not only regulate the emission of Tb ions 3+The luminescence intensity significantly enhances the scintillation luminescence performance of the glass-ceramic material, and also induces the transformation of BaAl2Si2O8 micron-sized crystals from monoclinic to hexagonal phase, improving the transmittance of the glass-ceramic material and achieving a balance between high crystallinity and high transparency, with a crystallinity ≥80% and a transmittance ≥70% at a wavelength of 543 nm. Within the temperature range of 303–523 K, the luminescence intensity of the glass-ceramic material of this invention exhibits resistance to thermal quenching and reversible thermal recovery properties. When applied to X-ray imaging, the spatial resolution of 16 LP / mm of this glass-ceramic material shows great potential in the field of static X-ray imaging. Attached Figure Description

[0019] Figure 1 XRD patterns of glass-ceramic samples from Comparative Example 1 and Examples 1-6, as well as standard diffraction cards for LaF3 crystal and monoclinic BaAl2Si2O8 (PDF 18-153) crystal;

[0020] Figure 2 XRD patterns of glass-ceramic samples from Comparative Example 2 and Examples 7-10, as well as standard diffraction cards for LaF3 crystal and hexagonal BaAl2Si2O8 (PDF 77-185) crystal;

[0021] Figure 3 Transmission spectra of glass-ceramic samples from Comparative Example 1 and Examples 1-6, and optical microscope photographs of glass-ceramic samples from Example 6.

[0022] Figure 4 Transmission spectra of glass-ceramic samples from Comparative Examples 2 and Examples 7-10, and optical microscope images of glass-ceramic sample from Example 10.

[0023] Figure 5 The image shown is a transmission electron microscope (TEM) image of the glass-ceramic sample from Example 6.

[0024] Figure 6 The image is a transmission electron microscope (TEM) image of the glass-ceramic sample from Example 10.

[0025] Figure 7 The room temperature emission spectra of the glass-ceramic samples from Comparative Examples 2 and Examples 7-10 are shown. Figure 7 The inset shows a comparison of the room temperature emission spectra of the glass-ceramic samples from Example 6 and Example 10;

[0026] Figure 8 The high-temperature dependent emission spectrum of the glass-ceramic sample of Example 10;

[0027] Figure 9 The image shows the X-ray excitation emission spectrum and imaging results of the glass-ceramic sample from Example 10. Detailed Implementation

[0028] The present invention will be further described in detail below with reference to the accompanying drawings, embodiments 1 to 10 and comparative examples 1 to 2.

[0029] I. Examples 1-10

[0030] The glass-ceramic materials in Examples 1-10 were all prepared using the following method:

[0031] 1) Raw material preparation:

[0032] The raw materials SiO2, LaF3, TbF3, Ba2CO3, and Al2O3 were prepared in the following proportions: SiO2, LaF3, and TbF3 were from Aladdin Company with a purity of 99.99%; Ba2CO3 and Al2O3 were from McLean Company with a purity of 99.99%.

[0033] Mix and grind the raw materials evenly in an agate mortar to obtain 15g of mixture, and carefully transfer it to an alumina crucible.

[0034] 2) Melting and quenching: Place the alumina crucible containing the raw material into a vertical heating furnace with a pre-set temperature of 1500℃, and then keep the alumina crucible at 1500℃ for 30 minutes. Then, quickly pour the molten material in the alumina crucible onto a stainless steel plate preheated to 350℃, and quickly press another stainless steel plate preheated to 350℃ onto the molten material to complete the quenching process and obtain solid block glass.

[0035] 3) Annealing: The solid block glass is placed in an annealing furnace for annealing at a temperature of 450°C for 3 hours. Finally, it is allowed to cool naturally to room temperature to obtain the precursor glass PG.

[0036] 4) Heat treatment: The precursor glass PG is cut into several small glass samples of uniform shape and size, and then placed in an annealing furnace for crystallization heat treatment at 720-790℃ for 2 hours. Finally, it is allowed to cool naturally to room temperature.

[0037] 5) Polishing: Using a mold, the glass sample is ground on sandpaper with roughness of 1000 grit, 2000 grit and 4000 grit respectively. Finally, polishing paper and polishing solution are used to polish the glass sample to make both sides of the glass sample flat and smooth, and finally obtain a glass ceramic sample with uniform shape and size and a thickness of 2mm.

[0038] The reason for using alumina crucibles in the above preparation process is that alumina crucibles not only have a high melting point, but their excellent resistance to fluorine corrosion and tolerance to alkaline oxides also ensure the accuracy of the glass formulation. Furthermore, their coefficient of thermal expansion is more compatible with glass, effectively preventing thermal stress cracking. They can meet the requirements of the entire process from melting to subsequent crystallization heat treatment, making them a reliable container choice for preparing this type of fluorine oxide glass ceramic. Therefore, alumina crucibles are used for melting throughout the above preparation process. In addition, annealing is used to remove internal stress, ensuring good machinability of the glass.

[0039] In the above preparation process, the vertical heating furnace used is the SJF1700 vertical resistance furnace manufactured by Nanjing Boyuntong Co., Ltd., and the annealing and heat treatment both use the LT 5 / 11 / P330 precision annealing furnace manufactured by Nabrizol GmbH, Germany.

[0040] II. Comparative Examples 1-2

[0041] Comparative Example 1: The difference from Examples 1-6 is that no heat treatment was performed, and no crystals precipitated in the glass. This Tb 3+ Under different doping concentrations, glass can precipitate LaF3 nanocrystals and monoclinic BaAl2Si2O8 micron crystals by heat treatment at different temperatures, forming a highly crystalline glass-ceramic with multi-scale bicrystalline phases.

[0042] Comparative Example 2: The difference from Examples 7-10 is that no heat treatment was performed, and no crystals precipitated in the glass. This Tb 3+ Under different doping concentrations, glass can precipitate LaF3 nanocrystals and hexagonal BaAl2Si2O8 micron crystals after heat treatment at different temperatures, forming a highly crystallizable and transparent glass-ceramic with multi-scale bicrystalline phases.

[0043] Naming of glass-ceramic material samples from Examples 1-6 and Comparative Example 1, and Tb 3+ The differences in doping concentration and preparation conditions are detailed in Table 1.

[0044] Table 1

[0045] Specific examples / naming <![CDATA[Tb 3+ Doping concentration (mol%) Heat treatment temperature (°C) Example 1 / T2-GC740 2 740 Example 2 / T2-GC750 2 750 Example 3 / T2-GC760 2 760 Example 4 / T2-GC770 2 770 Example 5 / T2-GC780 2 780 Example 6 / T2-GC790 2 790 Comparative Example 1 / T2-PG 2 0

[0046] Naming of glass-ceramic material samples from Examples 7-10 and Comparative Example 2, and Tb 3+ The differences in doping concentration and preparation conditions are detailed in Table 2.

[0047] Table 2

[0048] Specific examples / naming <![CDATA[Tb 3+ Doping concentration (mol%) Heat treatment temperature (°C) Example 7 / T22-GC720 22 720 Example 8 / T22-GC730 22 730 Example 9 / T22-GC740 22 740 Example 10 / T22-GC750 22 750 Comparative Example 2 / T22-PG 22 0

[0049] III. Analysis of Experimental Results

[0050] Performance tests were conducted on the above embodiments and comparative examples.

[0051] Figure 1 XRD patterns of the glass-ceramic samples from Comparative Example 1 and Examples 1-6, as well as standard diffraction cards for LaF3 crystal and monoclinic BaAl2Si2O8 (PDF 18-153) crystal. From... Figure 1 As can be seen from Comparative Example 1, only broadened and diffuse diffraction peaks are observed, confirming that the precursor glass without heat treatment is amorphous. As the heat treatment temperature increases from 740℃ to 790℃, the intensity of the weak diffraction peaks in the glass-ceramic sample significantly increases. Comparison with standard cards confirms that these diffraction peaks represent LaF3 crystals (PDF 82-690) and monoclinic BaAl2Si2O8 crystals. Furthermore, these diffraction peaks continuously enhance with increasing heat treatment temperature, indicating that the crystallinity of LaF3 nanocrystals and monoclinic BaAl2Si2O8 microcrystals in the glass-ceramic sample continuously increases (Examples 1-6). The crystallinity of the optimal sample (Example 6) is estimated to be approximately 85%. The crystallization process of the glass-ceramic samples can be summarized as follows: In the initial heat treatment stage, fluorite-structured LaF3 nanocrystals preferentially precipitate within the glass-ceramic samples; as the temperature rises to the critical point of 760℃, a secondary crystallization reaction occurs within the system, forming a multi-scale composite structure composed of monoclinic BaAl2Si2O8 micron-sized crystals and LaF3 nanocrystals. This indicates that the bicrystalline composite glass-ceramics can be controllably prepared by adjusting the temperature parameters.

[0052] Figure 2 XRD patterns of the glass-ceramic samples from Comparative Examples 2 and Examples 7-10, as well as standard diffraction cards for LaF3 crystal and hexagonal BaAl2Si2O8 (PDF 77-185) crystal. From... Figure 2 As can be seen from Comparative Example 2 (doped with high concentration of Tb) 3+The diffraction peaks were no longer broadened and diffused, but instead showed distinct crystalline diffraction peaks. Comparison with standard cards confirmed that these peaks belonged to LaF3 crystals (PDF 82-690). As the heat treatment temperature increased from 720℃ to 750℃, the intensity of the weak diffraction peaks in the glass-ceramic sample significantly increased. Comparison with standard cards confirmed that these peaks belonged to LaF3 crystals (PDF 82-690) and hexagonal BaAl2Si2O8 crystals (PDF 77-185), and this intensity continued to increase with increasing heat treatment temperature. The crystallinity of LaF3 nanocrystals and hexagonal BaAl2Si2O8 microcrystals in the glass-ceramic sample continuously increased (Examples 7-10). The estimated crystallinity of the optimal sample (Example 10) was approximately 83%. This is because the introduction of a large amount of TbF3 easily induces a structural phase transition. Therefore, after the introduced TbF3 reaches a critical value, the monoclinic BaAl2Si2O8 micron-sized crystals that precipitate first will gradually transform into hexagonal BaAl2Si2O8 micron-sized crystals during the subsequent high-temperature heat treatment. This indicates that the bicrystalline phase composite glass-ceramic can be controlled by adjusting the TbF3 concentration and temperature parameters, and the BaAl2Si2O8 crystal phase transformation can be controlled.

[0053] Figure 3 (a) Transmission spectra of the glass-ceramic samples of Comparative Example 1 and Examples 1-6 are shown. All samples exhibit characteristic absorption peaks at 350 nm, 368 nm, 377 nm, and 485 nm, corresponding to Tb, respectively. 3+ of 7 F6 → 5 L9, 5 D2、 5 D3 and 5 The D4 electronic transition has an optimal excitation peak at 377 nm. With the precipitation of second-phase monoclinic BaAl2Si2O8 micron-sized crystals in the glass-ceramic sample, the optical transmittance of the glass-ceramic sample decreases rapidly, especially for Example 6, where the transmittance drops to approximately 53%. Figure 3 (b) provides an optical microscope image of the glass-ceramic sample of Example 6, showing a monoclinic BaAl2Si2O8 micron-sized crystal formed inside the glass-ceramic.

[0054] Figure 4(a) shows the transmission spectra of the glass-ceramic samples of Comparative Examples 2 and Examples 7-10. The T22-GC750 bicrystalline glass-ceramic sample (Example 10) maintains a high transmittance of approximately 73% while retaining high crystallinity. This is because the LaF3 nanocrystals precipitated within the glass-ceramic sample significantly reduce Rayleigh scattering through size effects (much smaller than the visible light wavelength). Simultaneously, the hexagonal BaAl2Si2O8 microcrystals have a more symmetrical lattice structure compared to the monoclinic BaAl2Si2O8 microcrystals, and their refractive index matching with the glass phase creates a low-scattering-loss composite structure, thereby improving the overall transmittance of the glass-ceramic sample. Figure 4 The optical microscope image in (b) also shows that the hexagonal BaAl2Si2O8 micron crystals in the sample of Example 10 are about 50 μm in size.

[0055] and Figure 5 and Figure 6 TEM images show that the LaF3 nanocrystals in Examples 6 and 10 are spherical nanocrystals with a size of approximately 40–60 nm, uniformly distributed within the glass-ceramic structure. The corresponding high-resolution TEM images characterize these nanocrystals with clear lattice fringes. Further elemental mapping was used to perform micro-area elemental distribution scanning tests on the samples. The results showed that in Examples 6 and 10, La and F elements were enriched, overlapping with the distribution area of ​​the nanoparticles, indicating that the nanoparticles observed in the TEM images are LaF3 nanocrystals. Ba, Al, Si, and O elements were uniformly distributed in the samples. It is worth noting that only micrometer-sized spherical BaAl₂Si₂O₈ crystals were observed using optical microscopy. Figure 3 (b) and Figure 4 (b) indicates that only BaAl2Si2O8 micron-sized crystals were observed at the microscopic scale, while only LaF3 nanocrystals were observed at the TEM nanoscale. This seems to contradict the BaAl2Si2O8 / LaF3 biphase composite structure detected by XRD. However, the reason for this phenomenon is the significant size difference between the two phases. The LaF3 crystals are mainly dispersed in the matrix at the nanoscale, and their microscopic visibility is limited by the resolution of the optical microscope. In contrast, the micron-sized BaAl2Si2O8 crystals constitute the main phase in the microscopic optical image.

[0056] Figure 7 The images show the room-temperature emission spectra of the glass-ceramic samples from Comparative Example 2 and Examples 7-10. In Comparative Example 2, under 377 nm excitation, multiple distinct emission peaks appeared in the visible light band, with the optimal emission peak located at 543 nm. The characteristic emission peaks at 487, 543, 584, and 621 nm correspond to Tb. 3+ Ionic 5 D4→7 F J (J = 6, 5, 4, 3) energy level transitions. Furthermore, in the glass-ceramic samples of Examples 7-10, the luminescence intensity of the samples gradually increased with increasing heat treatment temperature. The reason for this phenomenon is that in Comparative Example 2, only a small amount of LaF3 nanocrystals precipitated, and only a small amount of Tb... 3+ It can enter LaF3 nanocrystals with low phonon energies, leaving a relatively large amount of Tb. 3+ The Tb remains in the high phonon energy glass phase, resulting in a relatively low green light emission intensity. However, as the heat treatment temperature gradually increases, more crystals precipitate inside the glass, leading to a higher concentration of Tb. 3+ The ability to penetrate the crystal reduces non-radiative relaxation, thereby enhancing luminescence. Furthermore, the multi-scale structure constructed by bicrystalline phase precipitation can further improve luminescence intensity by increasing the utilization rate of incident light. These phenomena demonstrate that the precipitation of LaF3 nanocrystals and BaAl2Si2O8 microcrystals can improve the luminescence intensity of glass-ceramic samples. Figure 7 The illustration compares 2 mol% Tb 3+ Doped sample T2-GC790 (Example 6) and 22 mol% Tb 3+ The room temperature emission spectrum of the doped sample T22-GC750 (Example 10) shows that the emission intensity of the T22-GC750 sample is significantly higher than that of the T2-GC790 sample.

[0057] To further test the thermal stability of the glass-ceramic samples, temperature-dependent spectral analysis was performed on the glass-ceramic samples of Example 10 within the temperature range of 303–523 K (e.g., temperature-dependent spectral analysis was performed). Figure 8 As shown in the figure, it was found that no significant thermal quenching phenomenon was observed under 377nm light excitation, and the luminescence intensity of the sample not only did not decrease, but actually showed a certain degree of enhancement. This unique phenomenon is mainly due to two key factors. First, Tb 3+ With [Xe]4f 8 The electronic configuration of the 4f orbital ensures stable interaction between the 4f electrons and the nucleus in the ground state, while in the excited state, the strong shielding effect of the 4f orbital makes it difficult for temperature changes to significantly affect its energy level structure, thus ensuring Tb 3+ Energy level stability at different temperatures ensures efficient and stable photon emission during the luminescence process. Secondly, ion substitution disrupts lattice symmetry and vibrational modes, leading to the formation of trap defects. These defects then release carrier recombination under thermal excitation, thereby releasing energy to Tb. 3+ The excitation energy level further promotes luminescence. This indicates that the highly crystalline transparent glass-ceramic material containing multi-scale bicrystalline phases of the present invention exhibits good resistance to thermal quenching.

[0058] To further test the scintillation luminescence properties of the highly crystalline transparent glass-ceramic material containing multi-scale bicrystalline phases of the present invention, the T22-GC750 sample (Example 10) was subjected to X-ray excitation. Figure 9 (a) XEL spectroscopy) and static X-ray imaging experiments Figure 9 (b)~(f)). The results show that the XEL integrated intensity of the T22-GC750 sample is 202% of that of a conventional scintillator BGO crystal. Imaging experiments show that the system can clearly present the internal structure of the packaged chip and capsule. Furthermore, imaging analysis of a standard X-ray test pattern plate shows that the system can still clearly resolve five rays at spatial frequencies exceeding 16 LP / mm, confirming the imaging capability of this glass-ceramic material.

Claims

1. A highly crystalline transparent glass-ceramic material containing multi-scale bicrystalline phases, characterized in that, The glass-ceramic material has the formula 20BaO-20Al2O3-20LaF3-40SiO2-xTbF3. LaF3 nanocrystals and BaAl2Si2O8 microcrystals are precipitated in the material, forming a multi-scale bicrystalline phase structure. The BaAl2Si2O8 microcrystals are hexagonal BaAl2Si2O8 crystals. Tb is doped in the form of TbF3 in the glass-ceramic material. 3+ Tb 3+ The doping concentration x is 2 < x ≤ 26 mol%, and the doped Tb 3+ Partially replacing La in the LaF3 nanocrystals 3+ Lattice sites and Ba in the BaAl2Si2O8 micron crystal 2+ Grid position.

2. The highly crystalline transparent glass-ceramic material containing multi-scale bicrystalline phases according to claim 1, characterized in that, The average size of the LaF3 nanocrystals is 30~60 nm, and the average size of the BaAl2Si2O8 microcrystals is 50~70 μm.

3. The highly crystalline transparent glass-ceramic material containing multi-scale bicrystalline phases according to claim 1, characterized in that, The LaF3 nanocrystals are hexagonal LaF3 crystal phase.

4. The highly crystalline transparent glass-ceramic material containing multi-scale bicrystalline phases according to claim 1, characterized in that, Tb 3+ When the doping concentration x is 22 mol%, the crystallinity of the glass-ceramic material is 80~85%, the transmittance of the glass-ceramic material at a wavelength of 543 nm is ≥70%, and the BaAl2Si2O8 micron crystal is a hexagonal BaAl2Si2O8 crystal phase.

5. The highly crystalline transparent glass-ceramic material containing multi-scale bicrystalline phases according to claim 1, characterized in that, Within a temperature range of 303~523 K, the luminescence intensity of the glass-ceramic material exhibits resistance to thermal quenching and reversible thermal recovery properties.

6. The highly crystalline transparent glass-ceramic material containing multi-scale bicrystalline phases according to claim 1, characterized in that, When the glass-ceramic material is used for X-ray imaging, its spatial resolution reaches 16 LP / mm.

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