Future applications for glass-ceramics are likely to capitalize on designed-in, highly specialized properties for the transmission, display, and storage of information. Glass-ceramics with microstructures comprised of uniformly dispersed crystals <100 nm in size offer promise for many potential new applications as well as provide unique attributes for many current products. This paper focuses on two types of nanocrystalline glass-ceramics: transparent glass-ceramics and tough, high-modulus glass-ceramics with precisely engineered surfaces. Transparent glass-ceramics are formed from certain aluminosilicate glasses capable of efficient crystal nucleation and slow growth. The key crystalline phases include β-quartz solid solutions, characterized by low-thermal-expansion behavior; spinel, with high hardness and elastic modulus; and mullite, which shows unique chromium-luminescence behavior.

Nanophase glass-ceramics

Novel Er3+-doped transparent NaYb2F7 glass-ceramics (GCs) were successfully fabricated for the first time by a conventional melt-quenching technique with subsequent heat treatment. The formation of NaYb2F7 nanocrystals (NCs) was confirmed by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), selected-area electron diffraction (SAED), and photoluminescence emission spectra. Moreover, the appearance of Stark level splitting of Er3+ emission bands and the variation of the decay curves demonstrate the accumulation of active centers into the NaYb2F7 NCs lattice. Hence, the photoluminescence emission intensities of Er3+ doped GC680 are greatly enhanced relative to those in precursor glass. Furthermore, the temperature dependent fluorescence intensity ratio (FIR) of thermally coupled emitting states (4S3/2, 2H11/2) in Er3+ doped GCs was studied under 980 nm laser excitation with a very low power density of 13 mW mm−2 to avoid the possible laser induced heating. A high temperature sensitivity of FIR of 1.36% K−1 is obtained at 300 K and the corresponding effective energy difference (ΔE) is 852 cm−1. Besides, laser induced heating at several excitation power densities was measured to evaluate the laser induced heating effect and the accuracy of temperature sensing for our sample. The GCs with relatively high sensitivity under low excitation power density are promising for temperature sensing. Moreover, the study on down-conversion (DC) spectra of the GC samples shows their ability to convert a high energy photon into two low energy photons, implying that they may also have important application as DC materials.

Luminescence properties of Er3+-doped transparent NaYb2F7 glass-ceramics for optical thermometry and spectral conversion

Effect of heat treatment on the structural and optical properties of tellurite glasses doped erbium

The optical properties of Ba2TiSi2O8 nanocrystals in transparent crystallized glasses were investigated. The transparent nanocrystallized glass with Ba2TiSi2O8 crystals having a particle size of ∼200nm was fabricated by crystallization (at 760 °C for 1 h) of a glass with the stoichiometric composition of Ba2TiSi2O8, i.e., 40BaO∙20TiO2∙40SiO2 glass. Both visible second-harmonic generation (green light, 532 nm) and luminescence (blue light, ∼470nm) could be observed in the transparent Ba2TiSi2O8 nanocrystallized glass, demonstrating the optical multifunctional nanocrystallized material. It was suggested that the blue luminescence from the transparent Ba2TiSi2O8 nanocrystallized glass originated from the oxygen-related defects of the SiO4 unit in the Ba2TiSi2O8 nanocrystals.

Second-order optical nonlinear and luminescent properties of Ba2TiSi2O8 nanocrystallized glass

Highly crystallinity transparent glass-ceramics based on MgO-Al2O3-SiO2-P2O5 system have been prepared by conventional melt-quenching and “two-step” crystallization method. The crystallization kinetics, phase evolution, structure, physical and light transmittance properties of glass-ceramics were studied. The results reveal that the crystallization mechanism of this glass is believed to be three-dimensional interfacial growth. The predominant crystalline phase is Mg2Al4Si5O18 in these glass-ceramics, and the content of crystalline phase becomes higher with rising of crystallization temperature and time, which the light transmittance of glass-ceramics decreases. It is observed that the main elements are uniformly distributed in glass-ceramics from EDS element distribution maps. All things considered, the optimal heat treatment schedule of parent glass is 840 °C/36 h + 1050 °C/3 h, the prepared glass-ceramics possesses high crystallinity (90.5 vol%), good light transmittance (85%) and excellent mechanical and thermal properties. These findings make this family of transparent glass-ceramics showing potential applications in solid-state optical functional material.

Crystallization, structure and characterization of MgO-Al 2 O 3 -SiO 2 -P 2 O 5 transparent glass-ceramics with high crystallinity

Transparent glass-ceramic is a new kind of functional material with homogenous and dense structure composed of fine crystal particles.Its preparation technique,species and properties were reviewed,and the development direction was discussed in the paper.

Pei Li-zhai

Papers

Transparent Glass-ceramics