Er3+,Er3+-Yb3+和Er3+-Na+掺杂CaF2透明陶瓷的光学性能

以Ca(NO3)2、Er(NO3)3、Yb(NO3)3、KF和NaF为原料,采用热压烧结方法制备出Er3+,Er3+-Yb3+和Er3+-Na+掺杂CaF2透明陶瓷。测试了样品室温吸收光谱和发射光谱。利用Judd-Ofelt理论分析了样品的光学性能,并对吸收光谱进行计算拟合,得到光谱参数?t (t=2,4,6),根据光谱参数?t计算出Er3+某些能级的的跃迁几率、荧光分支比、辐射寿命和品质因子,讨论并比较了Er3+-Yb3+和Er3+-Na+共掺对CaF2透明陶瓷光学性能的影响。结果表明：掺杂Yb3+和Na+改变了Er3+光谱参数;Er3+-Yb3+共掺有利于提高样品的荧光强度;Er3+-Na+共掺有利于提高荧光寿命。     

Novel Er3+/Ho3+‐codoped glass‐ceramic fibers for broadband tunable mid‐infrared fiber lasers

It is well recognized that a widely wavelength‐tunable mid‐infrared (MIR) fiber laser plays an important role in the development of compact and efficient coherent sources in the MIR range. Herein, the optimizing Er/Ho ratio for enhancement of broadband tunable MIR emission covering 2.6‐2.95 μm in the Er³⁺/Ho³⁺‐codoped transparent borosilicate glass‐ceramic (GC) fibers containing NaYF₄ nanocrystals under 980 nm excitation was investigated. Specifically, the obtained GC fibers with controllable crystallization and well fsd‐maintained structures were prepared by the novel melt‐in‐tube approach. Owing to the effective energy transfer between Er³⁺ and Ho³⁺ after crystallization, the 2.7 μm MIR emission was obviously enhanced and the emission region showed a notable extension from 2.6‐2.82 μm to 2.6‐2.95 μm after the addition of Ho³⁺. Importantly, we conducted a theoretical simulation and calculation related to the MIR laser performance, signifying that the GC fiber may be a promising candidate for MIR fiber laser. Furthermore, the melt‐in‐tube approach will provide a versatile strategy for the preparation of diverse optical functional GC fibers.     

Preparation and Structure of New Oxyfluoride Glass‐Ceramics Containing BaLiF3 Nanocrystal

Through a careful composition design, new oxyfluoride glass‐ceramics (GCs) containing BaLiF₃ nanocrystals with sizes of around 30 nm were prepared. Microstructural characterizations show interpenetrating phase separation in the sample with a composition of 15BaF₂–15ZnF₂–70SiO₂, after thermal treatment at 580°C for 40 h which leads to the nanocrystallization of BaLiF₃. The BaLiF₃ nanocrystals embedded in the glassy matrix could provide Ba or Li sites for the incorporation of optically active rare earth and transition‐metal ions, which provides a possibility to explore novel photonic properties by the codoping of rare earth and transition‐metal ions in GC materials.     

Effect of Microwave Processing on the Crystallization and Energy Density of BaO‐Na2O‐Nb2O5‐SiO2‐B2O3 Glass‐Ceramics

Barium sodium niobate (BNN) glass‐ceramics were successfully synthesized through a controlled crystallization method, using both a conventional and a microwave hybrid heating process. The dielectric properties of glass‐ceramics devitrified at different temperatures and conditions were measured. It was found that the dielectric constant increased with higher crystallization temperature, from 750°C to 1000°C, and that growth of the crystalline phase above 900°C was essential to enhancing the relative permittivity and overall energy storage properties of the material. The highest energy storage was found for materials crystallized conventionally at 1000°C with a discharge energy density of 0.13 J/cm³ at a maximum field of 100 kV/cm. Rapid microwave heating was found to not give significant enhancement in dielectric properties, and coarsening of the ferroelectric crystals was found to be critical for higher energy storage.     

Micro‐Raman Spectroscopy Study of Glass‐Ceramics with Gradient of Volume Fraction of Crystalline Phase

A simple technique to characterize the structure of nonuniform glass‐ceramics is proposed. The technique is based in micro‐Raman spectroscopy. This technique allows determining the gradient of average size of crystalline grains in the subsurface layers of glass‐ceramics modified by ion exchange.     

Transmission electron microscopic and optical spectroscopic studies of Ni2+/Yb3+/Er3+/Tm3+ doped dual‐phase glass‐ceramics

Ni²⁺/Yb³⁺/Er³⁺/Tm³⁺ codoped transparent glass‐ceramics (GCs) containing both hexagonal β‐YF₃ and spinel‐like γ‐Ga₂O₃ dual‐phase nanoparticles (NCs) are synthesized by melt‐quenching and subsequent heating procedures. Two techniques of transmission electron microscopy (TEM) nanoanalytics and optical spectroscopy are conjugated to understand the distribution of the rare‐earth ions (REs) and transition metals (TMs) in the nanostructured GCs. It is found that the REs are located predominantly in β‐YF₃, whereas the TMs in γ‐Ga₂O₃ NCs. As a result, energy transfer (ET) between the REs and TMs is considerably suppressed due to the large spatial separation (> 3 nm), but it is enhanced between the REs partitioned in the β‐YF₃ NCs. This has important implications for intended and demanding photoluminescence functions. For example, an ultrabroadband near‐infrared (NIR) emission in the wavelength region of 1000‐2000 nm covering the entire telecommunications window is observed for the first time. Meanwhile, intense upconversion (UC) emissions covering the 3 primary colors and locating in the first biological window can be also recorded under excitation by a single pump source at 980 nm.     

Glass‐Ceramics in the System BaO–SrO–ZnO–SiO2 with Adjustable Coefficients of Thermal Expansion

Glasses from the system BaO–SrO–ZnO–SiO₂ with different Ba/Sr ratios were characterized regarding crystallization behavior as well as the thermal expansion of almost fully crystallized glasses. Depending on the SrO concentration, different crystalline phases precipitate from the glasses. Those with low SrO concentrations precipitate crystals with the structure of low‐temperature BaZn₂Si₂O₇ as one of the major phases. Higher SrO concentrations cause the formation of Ba_1?xSr_xZn₂Si₂O₇ solid solutions with the structure of high‐temperature BaZn₂Si₂O₇. Both, the low‐ as well as the high‐temperature phase exhibit very different thermal expansion behaviors ranging from a very high coefficient of thermal expansion in the case of the low‐temperature phase to a very low coefficient of thermal expansion in the case of the high‐temperature phase. The glass‐ceramics with the highest and that with the lowest coefficient of thermal expansion measured between 100°C and 800°C show a difference of 7.9 × 10^?6 K^?1, which is caused solely by a substitution of BaO with SrO. In contrast, the maximum variation in the thermal expansion of the glasses was only 1.5 × 10^?6 K^?1. The microstructure of sintered and afterward crystallized glass powders was analyzed via scanning electron microscopy and showed crack‐free samples with low porosity.     

Sealing Glass‐Ceramics with Near‐Linear Thermal Strain,Part II: Sequence of Crystallization and Phase Stability

The sequence of crystallization in a recrystallizable lithium silicate sealing glass‐ceramic Li₂O–SiO₂–Al₂O₃–K₂O–B₂O₃–P₂O₅–ZnO was analyzed by in situ high‐temperature X‐ray diffraction (HTXRD). Glass‐ceramic specimens have been subjected to a two‐stage heat‐treatment schedule, including rapid cooling from sealing temperature to a first hold temperature 650°C, followed by heating to a second hold temperature of 810°C. Notable growth and saturation of Quartz was observed at 650°C (first hold). Cristobalite crystallized at the second hold temperature of 810°C, growing from the residual glass rather than converting from the Quartz. The coexistence of quartz and cristobalite resulted in a glass‐ceramic having a near‐linear thermal strain, as opposed to the highly nonlinear glass‐ceramic where the cristobalite is the dominant silica crystalline phase. HTXRD was also performed to analyze the inversion and phase stability of the two types of fully crystallized glass‐ceramics. While the inversion in cristobalite resembles the character of a first‐order displacive phase transformation, i.e., step changes in lattice parameters and thermal hysteresis in the transition temperature, the inversion in quartz appears more diffuse and occurs over a much broader temperature range. Localized tensile stresses on quartz and possible solid‐solution effects have been attributed to the transition behavior of quartz crystals embedded in the glass‐ceramics.     

Porous,Sintered Glass‐Ceramics from Inorganic Polymers Based on Fayalite Slag

The present paper deals with the synthesis of porous, sintered glass‐ceramics obtained at temperatures below 1150°C, originating from inorganic polymers based on fayalite slag. Firing led to the evaporation of water, dehydroxylation, and oxidation of Fe²⁺ above 345°C. For heating >700°C, the Si–O stretching band shifted from the 1160 and 750 cm^?1 to the 1255 and 830 cm^?1 region, due to a structural reorganization of the amorphous phase, whereas Fe–O bands appeared at 550 cm^?1. The final microstructure consisted predominantly of an amorphous phase, hematite, and franklinite. The open porosity and compressive strength decreased and increased, respectively, as the firing temperature increased. The final values suggest properties comparable to that of structural lightweight concrete, still, the materials synthesized herein, are lighter, and made primarily from secondary resources.     

Controllable Formation of the Crystalline Phases in Ge–Ga–S Chalcogenide Glass‐Ceramics

We prepared chemically stoichiometric, S‐poor and S‐rich Ge–Ga–S glasses and annealed them at a temperature that was 20°C higher than its respective glass transition temperature. We aimed at tuning the formation of the different crystals in chalcogenide glass‐ceramics. Through systematic characterization of the structure using X‐ray diffraction and Raman scattering spectra, we found that, GeS₂ and GeS crystals only can be created in S‐rich and S‐poor glass‐ceramics, respectively, while all GeS, Ga₂S₃, and GeS₂ crystals exist in chemically stoichiometric glass‐ceramics. Moreover, we demonstrated the homogeneous distribution of the crystals can be formed in the S‐rich glass‐ceramics from the surface to the interior via composition designing. The present approach blazes a new path to control the growth of the different crystals in chalcogenide glass‐ceramics.     

Optical Thermometry Based on Up‐Conversion Luminescence Behavior of Er3+ ‐Doped Transparent Sr2YbF7 Glass‐Ceramics

Transparent novel glass‐ceramics containing Sr₂YbF₇:Er³⁺ nanocrystals were successfully fabricated by melt‐quenching technique. Their structural and up‐conversion luminescent properties were systemically investigated by XRD, HRTEM, and a series of spectroscopy methods. The temperature‐dependent up‐conversion spectra prove that ²H_11/2 and ⁴S_3/2 levels of Er³⁺ are thermally coupled energy levels (TCEL). Consequently, the ²H_11/2 → ⁴I_15/2 and ⁴S_3/2 → ⁴I_15/2 emissions of Er³⁺ in Sr₂YbF₇:Er³⁺ glass‐ceramics can be used as optical thermometry based on fluorescence intensity ratio (FIR) technique. Combined with low phonon energy and high thermal stability, Er³⁺ ions in Sr₂YbF₇ glass‐ceramics present broad operating temperature range (300–500 K), large energy gap of TCEL (786 cm^?1) and high theoretical maximum value of relative sensitivity (62.14 × 10^?4 K^?1 at 560 K), which suggests that Sr₂YbF₇:Er³⁺ glass‐ceramics may be excellent candidates for optical temperature sensors.     

Er3+ Ions‐Doped Germano‐Gallate Oxyfluoride Glass‐Ceramics Containing BaF2 Nanocrystals

Er³⁺ ions‐doped germano‐gallate oxyfluoride glass‐ceramic containing BaF₂ nanocrystals was prepared through conventional melt quenching and subsequent thermal treatment method. X‐ray diffraction patterns and transmission electron microscope images confirmed the formation of BaF₂ nanocrystals in glass‐ceramics. Preferential incorporation of Er³⁺ ions into the BaF₂ nanocrystals were confirmed by the absorption spectra and emission spectra, and enhanced upconversion emission and infrared emission were observed. Relatively high transmittance in the mid‐infrared region indicated great potential of this germano‐gallate oxyfluoride glass‐ceramics as host materials for the efficient mid‐infrared emission from rare‐earth ions.     

Effect of P2O5 on the Structural and Magnetic Properties of Magnetite‐Based Glass‐Ceramics

The specific morphology and magnetic properties of magnetite‐based glass‐ceramics obtained by crystallization of Fe‐containing borosilicate glassmelts in the presence of P₂O₅ as nucleating agent are investigated. We found that the distribution of the tiny nanoparticles of magnetite determines the low temperature response to magnetic field. The observed effects are discussed with respect to the following factors: (1) the existence of a multimodal size distribution of the tiny grains as revealed by Mössbauer spectroscopy, magnetometry, and high‐resolution electron microscopy; (2) the existence of a disordered layer at the grain surface which is driven by field in a magnetically ordered state; and (3) the interplay between the relaxation mechanisms in different temperature ranges.     

Sealing Glass‐Ceramics with Near Linear Thermal Strain,Part I: Process Development and Phase Identification

A widely adopted approach to form matched seals in metals having high coefficient of thermal expansion (CTE), e.g. stainless steel, is the use of high CTE glass‐ceramics. With the nucleation and growth of Cristobalite as the main high‐expansion crystalline phase, the CTE of recrystallizable lithium silicate Li₂O–SiO₂–Al₂O₃–K₂O–B₂O₃–P₂O₅–ZnO glass‐ceramic can approach 18 ppm/°C, matching closely to the 18 ppm/°C–20 ppm/°C CTE of 304L stainless steel. However, a large volume change induced by the α‐β inversion between the low‐ and high‐ Cristobalite, a 1^st order displacive phase transition, results in a nonlinear step‐like change in the thermal strain of glass‐ceramics. The sudden change in the thermal strain causes a substantial transient mismatch between the glass‐ceramic and stainless steel. In this study, we developed new thermal profiles based on the SiO₂ phase diagram to crystallize both Quartz and Cristobalite as high expansion crystalline phases in the glass‐ceramics. A key step in the thermal profile is the rapid cooling of glass‐ceramic from the peak sealing temperature to suppress crystallization of Cristobalite. The rapid cooling of the glass‐ceramic to an initial lower hold temperature is conducive to Quartz crystallization. After Quartz formation, a subsequent crystallization of Cristobalite is performed at a higher hold temperature. Quantitative X‐ray diffraction analysis of a series of quenched glass‐ceramic samples clearly revealed the sequence of crystallization in the new thermal profile. The coexistence of two significantly reduced volume changes, one at ~220°C from Cristobalite inversion and the other at ~470°C from Quartz inversion, greatly improves the linearity of the thermal strains of the glass‐ceramics, and is expected to improve the thermal strain match between glass‐ceramics and stainless steel over the sealing cycle.     

Rare‐earth‐doped SiO2‐CaF2 glass ceramic nano‐particle with upconversion properties

Rare‐earth‐doped upconversion nano‐phosphor shows new possibilities in the field of bioimaging because of its unique properties like higher penetration depth, low signal to noise ratio (SNR), good photo stability, and zero auto fluorescence. The oxyfluoride glass system is the combination of both fluoride and oxide where fluoride host offers high optical transparency due to low phonon energy and oxide network offers high physical stability. Thus, in the present work, an attempt has been made to synthesize 1 mol% Er³⁺ doped SiO₂‐CaF₂ glass ceramic nano‐particles through sol‐gel route. The synthesized glass ceramic particles were heat treated at 4 different temperatures starting from 600°C to 900°C.The X‐ray diffraction (XRD) analysis and Transmission electron microscopy (TEM) analysis confirmed the formation of CaF₂ nano‐crystals in the matrix which is 20‐30 nm in size. The vibrational spectroscopic analysis of the glass ceramics sample has been investigated by Fourier transform infrared (FTIR) spectroscopy. The UV‐Visible‐NIR spectroscopy analysis was carried out to analyze the absorption intensity in the near infrared region. Upon 980 nm excitation, the sample shows red emission corresponds to ⁴F_9/2→⁴I_15/2 energy level transition. The prepared nano‐particles showed excellent biocompatibility when tasted on MG‐63 osteoblast cells.     

Effect of ligand field symmetry on upconversion luminescence in heat‐treated LaBGeO5:Yb3+, Er3+ glass

In this paper, we report upconversion (UC) luminescence enhancement in LaBGeO₅:Yb³⁺, Er³⁺ glass‐ceramics (GCs), surface crystallized glass‐ceramics (SCGCs) and ceramics compared with the as‐melt glass fabricated by the conventional melt‐quenching technique. Based on structural investigations, we find that the nucleation and crystallization of trigonal stillwellite LaBGeO₅:Yb³⁺, Er³⁺ nanocrystals occur first at the glass surface before the following volume crystallization. The local site symmetry around rare earth (RE) ions which was evaluated using the Eu³⁺ ions as a probe together with Judd‐Ofelt theory calculations exhibits a clear increase with the devitrification of the glass. Consequently, complete crystallization of the glass leads to largest enhancement in the UC emissions of the LaBGeO₅:Yb³⁺, Er³⁺ ceramics. We ascribe the enhancement of UC luminescence in the LaBGeO₅:Yb³⁺, Er³⁺ GCs, SCGCs, and ceramics to the structural ordering and the improvement of site symmetry surrounding RE ions that minimizes the rate of nonradiative relaxation process.     

Effects of Nd Content on Structure and Chemical Durability of Zirconolite–Barium Borosilicate Glass‐Ceramics

The effects of Nd₂O₃ content (0–12 wt %) on crystalline phases, microstructure, and chemical durability of barium borosilicate glass‐ceramics belonging to SiO₂–B₂O₃–Na₂O–BaO–CaO–TiO₂–ZrO₂–Nd₂O₃ system were studied. The results show that the glass‐ceramics with 2–6 wt% of Nd₂O₃ possess mainly zirconolite and titanite phases along with a small amount baddeleyite phase in the bulk. Calcium titanate appears when the Nd₂O₃ content increases to 8 wt%, and the amount of quadrate calcium titanate crystals increases with further increasing content of Nd₂O₃. For the glass‐ceramics with 6 wt% Nd₂O₃ (Nd‐6), Nd elements homogeneously distribute in zirconolite, titanite, and residual glass phases. There is a strong enrichment of Nd in calcium titanate crystals for the sample with 10 wt% Nd₂O₃. The viscosity of Nd‐6 glass is about 49 dPa·s at 1150°C. Moreover, Nd‐6 glass‐ceramics show the lower normalized leaching rates of B (LR_B), Ca (LR_Ca), and Nd (LR_Nd) when compared to that of the sample with 8 wt% Nd₂O₃. After 42 days, LR_B, LR_Ca, and LR_Nd of the Nd‐6 glass‐ceramics are about 6.8 × 10^?3, 1.6 × 10^?3, and 4.4 × 10^?6 g·m^?2·d^?1, respectively.     

Elaboration,Structure, and Intense Upconversion in Transparent KYb2F7:Ho3+ Glass‐Ceramics

Novel transparent oxyfluoride glass‐ceramics containing KYb₂F₇:Ho³⁺ nanocrystals were successfully elaborated by melt‐quenching technique with further thermal treatment for the first time. Their structural and luminescent properties were investigated systemically by XRD, HRTEM, absorption spectra, upconversion spectra, and lifetime measurements. Under 980 nm laser excitation, all samples exhibited characteristic emissions of Ho³⁺. Attractively, the upconversion emissions of Ho³⁺, especially green and near‐infrared emissions, were enormously enhanced 190 times after crystallization. The incorporation of Ho³⁺ into KYb₂F₇ nanocrystals with lower phonon energy was responsible for this phenomenon. Our research may enrich the understanding of fluoride‐nanocrystals‐based transparent oxyfluoride glass‐ceramics.     

Microwave Dielectric Properties of Novel Glass‐Free Low‐Firing Li2CeO3 Ceramics

Novel glass–free low temperature firing microwave dielectric ceramics Li₂CeO₃ with high Q prepared through a conventional solid‐state reaction method had been investigated. All the specimens in this paper have sintering temperature lower than 750°C. XRD studies revealed single cubic phase. The microwave dielectric properties were correlated with the sintering conditions. At 720°C/4 h, Li₂CeO₃ ceramics possessed the excellent microwave dielectric properties of ε_r = 15.8, Q × f = 143 700 (GHz), and τ_f  = ?123 ppm/°C. Li₂CeO₃ ceramics could be excellent candidates for glass‐free low‐temperature co‐fired ceramics substrates.