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.

Transparent Glass-ceramics

Spectroscopic and photoluminescence characteristics of Sm3+ doped calcium aluminozincate phosphor for applications in w-LED

Spectroscopic studies of Dy3+ doped borate glasses for cool white light generation

The precursor glass in the ZnO–Al2O3–B2O3–SiO2 (ZABS) system doped with Eu2O3 was prepared by the melt-quench technique. The transparent willemite, Zn2SiO4 (ZS) glass–ceramic nanocomposites were derived from this precursor glass by a controlled crystallization process. The formation of willemite crystal phase, size, and morphology with increase in heat-treatment time was examined by X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM) techniques. The average calculated crystallite size obtained from XRD is found to be in the range 18–70 nm whereas the grain size observed in FESEM is 50–250 nm. The refractive index value is decreased with increase in heat-treatment time which is caused by the partial replacement of ZnO4 units of ZS nanocrystals by AlO4 units due to generation of vacancies. Fourier transform infrared (FTIR) reflection spectroscopy was used to evaluate its structural evolution. Vickers hardness study indicates marked improvement of hardness in the resultant glass-ceramics compared with its precursor glass. The photoluminescence spectra of Eu3+ ions exhibit emission transitions of 5D0→7Fj (j = 0, 1, 2, 3, and 4) and its excitation spectra show an intense absorption band at 395 nm. These spectra reveal that the luminescence performance of the glass–ceramic nanocomposites is enhanced up to 17-fold with the process of heat treatment. This enhancement is caused by partitioning of Eu3+ ions into glassy phase instead of into the willemite crystals with progress of heat treatment. Such luminescent glass–ceramic nanocomposites are expected to find potential applications in solid-state red lasers, phosphors, and optical display systems.

Thermal, Structural, and Enhanced Photoluminescence Properties of Eu3+-doped Transparent Willemite Glass–Ceramic Nanocomposites

Fabrication and enhanced photoluminescence properties of Sm3+-doped ZnO–Al2O3–B2O3–SiO2 glass derived willemite glass–ceramic nanocomposites

The sintering characteristics, phase composition, microstructure and optical properties of 1:1 ZnAl2O4 spinel doped with Ti4+ from 1.125 to 4.5 mole-% synthesized through coprecipitation were investigated in this study. Effective densification was achieved at a low sintering temperature, 1350°C after 1 h. Powder XRD patterns revealed that, besides ZnAl2O4 spinel and rutile as major crystalline phases, minor Zn2Ti3O8 phase was present in the sintered system, with its extent depending on the TiO2 content and sintering temperature. SEM micrographs demonstrated a coherent and uniformly distributed fine-grained microstructure in the fracture surfaces of the sintered Ti4+ doped ZnAl2O4 spinel ceramics body. The Tauc plot of Ti4+ doped ZnAl2O4 spinel exhibited a leftward shift of the band gap from 3.79 to 3.48 eV with increase of Ti4+ content from 0 to 4.5 mole-%. Ti4+ was observed to function as a normal grain growth accelerator during ZnAl2O4 sintering. This was probably due to enhanced grain boundary diffusion.

Structural and Optical Properties of Ti 4+ Doped Sintered ZnAl 2 O 4 Ceramics

Abstract: ZnAl 2 O 4 spinel precursor powders (mole ratio ZnO : Al 2 O 3 = 1 : 1) doped with 0.5–2.0 mass-% Zr ions were synthesized by the coprecipitation route. The derived powders were uniaxially pressed into cylindrical pellets and sintered at 1350 °C for 1 h. The sintering behaviour, phase assemblage and microstructure of fired ZnAl 2 O 4 ceramics doped with different concentrations of Zr were investigated. Sintered density above 97 % of the theoretical density of pure ZnAl 2 O 4 ceramics was achieved with the addition of 2.0 % Zr . The residual flexural strength of the sintered body was as high as 120 kg.cm for the highest addition of Zr, and it was higher than that of the Ti doped ZnAl 2 O 4 . The powder XRD patterns of sintered compacts revealed that besides ZnAl 2 O 4 spinel as the major crystalline phase, a minor amount of tetragonal ZrO 2 phase is also present when the dopant quantity is higher. The SEM micrographs of the fractured surfaces of the sintered body demonstrated a coherent and uniform microstructure with a homogeneous distribution of microfine grains with Zr-doped ZnAl 2 O 4 compacts.

Effect of Zr4+ Dopant on Microstructure, Densification and Thermomechanical Behaviour of ZnAl2O4 Spinel

This paper deals with the preparation and evaluation of a zeolite prototype developed from an aluminosilicate precursor for its possible application as a hydrocracking catalyst. Aluminium nitrate and tetraethyl orthosilicate at definite proportions were the primary reagents for the gel synthesis. Nickel loading and stipulated post-synthesis treatment of the material are also addressed in this paper. The characteristics of the calcined aluminosilicate gel were estimated using X-ray diffraction (XRD), scanning electron microscope (SEM) study with energy dispersive spectroscopy (EDS), differential thermal analysis (DTA) with thermogravimetry (TG) and Fourier-transformed infrared spectroscopy (FTIR) at different temperatures. A preliminary laboratory-scale investigation of hydrocracking performance of this zeolite prototype was also conducted.

Synthesis and characterization of a sol-gel-derived zeolite prototype as a prospective hydrocracking catalyst

Polymeric monolithic doped zirconia and zirconia-alumina stiff gels (via stable zirconia and zirconia-alumina sols respectively), derived from Zr-n-propoxide, acetyl acetone, aluminium chloride, di-methyl formamide etc with judicious time-temperature-pH selection, have been prepared by controlled hydrolysis and polycondepsation, and subsequently subjected to heat treatment at 1300°C. The crystallization behaviour of the gels was studied by X-ray powder diffraction and differential thermal analysis. For the dried (25°C) composite gels pore size distributions were estimated. FTIR spectra (at 25° and 200°C) and scanning electron microscopy (at 25° and 1300°C) of both types of gels revealed that low temperature sintering is influenced by the addition of alumina sol in doped zirconia sol matrix to result in a better monolithicity. The microhardness of the fired composite gel was also determined.

Sunanda Mukhopadhyay

Papers

Structural and Optical Properties of Ti 4+ Doped Sintered ZnAl 2 O 4 Ceramics

Effect of Zr4+ Dopant on Microstructure, Densification and Thermomechanical Behaviour of ZnAl2O4 Spinel

Synthesis and characterization of a sol-gel-derived zeolite prototype as a prospective hydrocracking catalyst

Crystallization Behaviour of Monolithic Doped Zirconia and Zirconia-Alumina Composite Gels