Zn2SiO4 Crystal Research Articles

Highly Stable Propane Dehydrogenation on a Self‐Supporting Single‐Component Zn2SiO4 Catalyst

AbstractCurrent industrial propane dehydrogenation (PDH) processes predominantly use either toxic Cr‐based or expensive Pt‐based catalysts, necessitating urgent exploration for alternatives. Herein, we present Zn2SiO4, an easily prepared, cost‐effective material, as a highly efficient and stable catalyst for PDH. Uniquely, Zn2SiO4 nanocrystals do not require dispersion on support materials, commonly needed for catalytic active oxide clusters, but function as a self‐supporting catalyst instead. During the reaction‘s induction period, surface Zn species on the Zn2SiO4 crystal reduce to coordinately unsaturated ZnOx single sites, serving as highly active catalytic centers. The Zn2SiO4 catalyst demonstrates a stable performance over 200 hours of PDH operation at 550 °C. We further find that introducing a minuscule amount of CO2 into the propane feed significantly extends the catalyst lifespan to over 2000 hours. This enhancement arises from the special role of CO2 in facilitating the removal of strongly adsorbed H*, preventing the complete reduction of ZnOx. After prolonged reaction, the activity of Zn2SiO4 can be fully restored by etching the surface layer to expose fresh Zn species, available throughout the crystals. The combination of CO2introduction and catalytic site regeneration strategies is expected to enable a year‐long PDH operation using a single batch of Zn2SiO4 catalyst.

Highly Stable Propane Dehydrogenation on a Self-Supporting Single-Component Zn2SiO4 Catalyst.

Current industrial propane dehydrogenation (PDH) processes predominantly use either toxic Cr-based or expensive Pt-based catalysts, necessitating urgent exploration for alternatives. Herein, we present Zn2SiO4, an easily prepared, cost-effective material, as a highly efficient and stable catalyst for PDH. Uniquely, Zn2SiO4 nanocrystals do not require dispersion on support materials, commonly needed for catalytic active oxide clusters, but function as a self-supporting catalyst instead. During the reaction's induction period, surface Zn species on the Zn2SiO4 crystal reduce to coordinately unsaturated ZnOx single sites, serving as highly active catalytic centers. The Zn2SiO4 catalyst demonstrates a stable performance over 200 hours of PDH operation at 550 °C. We further find that introducing a minuscule amount of CO2 into the propane feed significantly extends the catalyst lifespan to over 2000 hours. This enhancement arises from the special role of CO2 in facilitating the removal of strongly adsorbed H*, preventing the complete reduction of ZnOx. After prolonged reaction, the activity of Zn2SiO4 can be fully restored by etching the surface layer to expose fresh Zn species, available throughout the crystals. The combination of CO2introduction and catalytic site regeneration strategies is expected to enable a year-long PDH operation using a single batch of Zn2SiO4 catalyst.

Enlightening the structural, elastic, and luminescence properties of transparent Zn2SiO4 glass-ceramic by precipitation of Gd2O3 as dopant

This work focus on fabrication of new Gd3+-doped willemite (Zn2SiO4) glass-ceramics derived from the Gd2O3–ZnO–Al2O3–B2O3–SiO2 (Gd-ZABS) glass system by a controlled sintering process. The physical characteristic with formation of Gd3+-doped Zn2SiO4 glass-ceramic crystal phase, morphology and structural changes were examined by Archimedes method, X-ray diffraction (XRD), Field Emission Scanning Electron Microscope (FESEM) and Fourier-transform infrared (FTIR) reflection spectroscopy. The appearance of SiO2, ZnO4 and Zn–O–Si bands indicate that the formation of Zn2SiO4 crystal phase. As for elastic analysis, the ultrasonic velocity and elastic coefficients showed an increasing tendency with the increase in sintering temperature. The study on energy transfer has found that the optical band gap of Gd3+-doped Zn2SiO4 glass-ceramic has decreased as the sintering temperature increased. The luminescence spectra of Gd3+-doped Zn2SiO4 exhibit several strong emission peak located at 425, 447, 462, 485 and 530 nm after the samples were subjected to 310 nm excitation source. Prominent green emission of Gd3+-doped Zn2SiO4 glass-ceramic were strongly observed at 530 nm. These spectra show that when the sintering temperature increases, the luminescence performance of the glass-ceramics has improved.

Effect of properties and crystallization behavior of BaO–ZnO–B2O3–SiO2 glass on the electrical conductivity of Cu paste

AbstractThe extensive application of multilayer ceramic capacitors provides an attractive development for terminal electrode pastes. However, the growing requirement for advanced glass materials used in terminal electrode pastes is substantiated. Therefore, to advance the development of electrode pastes, better development and deeper exploration of glass powder are required. Here, a series of BaO–ZnO–B2O3–SiO2 (BZBS) glasses were prepared by melt‐quenching technique, which are used to investigate the effect of the introduction of BaO on structure and properties of the ZnO–B2O3–SiO2 (ZBS) glass. With the introduction of BaO, the relative amount of [BO4] was much less, which made the glass network structure loosen, decreased the glass transition temperature (Tg) and increased the coefficient of thermal expansion of the glass. The decreasing contact angle was observed on the surface of a barium titanate (BaTiO3) substrate. When the BaO content was around 3–7 mol%, the stability of ZBS glass frit could be strengthened by inhibiting the precipitation of Zn2SiO4 crystal. In addition, to further characterize the effect of glass on terminal electrode paste, BZBS glass powder was adopted to prepare copper electrode paste, which was printed on the BaTiO3 substrate and subsequently fired at 800°C for 10 min. With the related copper paste containing ZBS glass doped with 7 mol% BaO, the optimum value of acid resistance and sheet resistance (1.99 mΩ) were exhibited, at which the coated copper paste formed a dense conducting layer.

Structural, morphological, and optical properties of Co‐ substituted Zn2SiO4 nanopowders prepared by a hydrothermal-assisted sol-gel process

Cobalt-substituted zinc orthosilicate pigments were obtained by pyrolysis of precursors synthesized by a convenient hydrothermal-assisted sol-gel process without using any toxic or expensive chemical (e.g., silicon alkoxides). XRD investigation confirms that the Co2+ ions are successfully incorporated into the Zn2SiO4 crystal. Rietveld refinement data reveals that unit-cell parameters increase with Co-content in Zn2-xCoxSiO4 solid-solutions. The homogeneous pigments are composed of largely agglomerated primary particles having a size less than 70 nm. The UV–visible spectroscopy shows that the blue color of pigments is caused by the presence de Co2+ in tetrahedral sites of Zn2+. The colorimetric parameters indicate that a blue pigment could be achieved with the only x = 0.05. A content of less than 5 wt% of the prepared pigments gives a deep blue hue to ceramic glazes. Cobalt-substituted Zn2SiO4 pigments exhibit high coloring performance and a relatively less cobalt content, which make them promising pigments for ceramic tiles.

A novel approach to the preparation of manganese - doped zinc silicate luminescent material according to the precipitation method

The purpose of this work is to study the effect of some precipitation conditions on the luminescent properties of manganese-doped zinc silicate when synthesized in a new approach - impregnated precipitation method. The samples are characterized by thermal analysis, infrared IR, luminescent spectrum (PL), X-ray diffraction spectrum and scanning electron microscope (SEM). The results showed that manganese - doped zinc silicate luminescent material prepared by the impregnated precipitation method has higher luminescence than the traditional co-precipitation method. Samples with the highest luminescent properties were synthesized under the following conditions: concentration of Zn (CH3COO)2 is 1M, the precipitate aging time of 20 minutes, the washed filtered precipitate, impregnated with Mn2+ with a content of 1.5 % mol compared to the total metal, dried at 80 °C and then heat at 900 0C for 45 minutes. The obtained product is single-phase zinc silicate with composition of Zn1,97Mn0,03SiO4, rhombic structure with most particles varying in size of 0.3 - 0.5 µm, emitting green light with λmax = 525 nm when excited by UV rays with wavelength of 254 nm. Forming a single-phase Zn2SiO4 crystal at 900 0C for 45 minutes allowed to reduce the energy required for the sintering process compared with the solid - phase reaction method.

Influence of Calcination Temperature on Crystal Growth and Optical Characteristics of Eu3+ Doped ZnO/Zn2SiO4 Composites Fabricated via Simple Thermal Treatment Method

This research paper proposes the usage of a simple thermal treatment method to synthesis the pure and Eu3+ doped ZnO/Zn2SiO4 based composites which undergo calcination process at different temperatures. The effect of calcination temperatures on the structural, morphological, and optical properties of ZnO/Zn2SiO4 based composites have been studied. The XRD analysis shows the existence of two major phases which are ZnO and Zn2SiO4 crystals and supported by the finding in the FT-IR. The FESEM micrograph further confirms the existence of both ZnO and Zn2SiO4 crystal phases, with progress in the calcination temperature around 700–800 °C which affects the existence of the necking-like shape particle. Absorption humps discovered through UV-Vis spectroscopy revealed that at the higher calcination temperature effects for higher absorption intensity while absorption bands can be seen at below 400 nm with dropping of absorption bands at 370–375 nm. Two types of band gap can be seen from the energy band gap analysis which occurs from ZnO crystal and Zn2SiO4 crystal progress. It is also discovered that for Eu3+ doped ZnO/Zn2SiO4 composites, the Zn2SiO4 crystal (5.11–4.71 eV) has a higher band gap compared to the ZnO crystal (3.271–4.07 eV). While, for the photoluminescence study, excited at 400 nm, the emission spectra of Eu3+ doped ZnO/Zn2SiO4 revealed higher emission intensity compared to pure ZnO/Zn2SiO4 with higher calcination temperature exhibit higher emission intensity at 615 nm with 700 °C being the optimum temperature. The emission spectra also show that the calcination temperature contributed to enhancing the emission intensity.

Comprehensive study on structural and optical properties of Tm2O3 doped zinc silicate based glass–ceramics

In this research, Tm2O3 doped zinc silicate based glass–ceramics were prepared by using conventional melt-quenching method and has been successfully derived from ZnO-WRHA glasses with control heat treatment process. The formation of zinc silicate phase affected by heat treatment process was investigated using X-ray diffraction. Fourier transform infrared reflection spectroscopy (FTIR) analysis was used to determine the crystallization of Zn2SiO4 in the glass matrix. FTIR analysis showed the appearance of Zn2SiO4 and SiO2 bands that supported the formation of Zn2SiO4 crystal phase in the glass matrix. The optical absorption and energy band gap of the glass and glass–ceramics was investigated using UV–Vis spectroscopy. The absorption edge shows the movement towards longer wavelength with increasing heat treatment temperature. Besides, the energy band gap decreased with the progression of heat treatment. This ability to enhance optical properties in glass–ceramics was expected to have bright future in the opto-electronics devices.

Growth-front hopping via stress-induced nucleation illustrated for the crystallization of Ba1-xSrxZn2Si2O7 from a glass in the BaO-SrO-ZnO-SiO2 system

The effect of P2O5 and Ce2O3 on the crystallization behavior of a BaO-SrO-ZnO-SiO2 glass was investigated using thermal analyses, X-ray diffraction, scanning electron microscopy including electron backscatter diffraction as well as laser scanning microscopy. Heat treatments lead to the precipitation of Ba1-xSrxZn2Si2O7, Zn2SiO4, and CeO2 at the surface. While Zn2SiO4 crystals form 1 µm deep immersions in the surface, CeO2 crystals originate from near-surface areas. The star-shaped CeO2 crystals show mostly three different orientations, among which the <001>- or <111>-orientation perpendicular to the surface are clearly preferred. In the bulk, many (Ba, Sr)5(PO4)3Cl crystals are observed acting as nucleation sites for Ba1-xSrxZn2Si2O7. This nucleation process is clearly facilitated by the occurring stresses. Moreover, an epitaxial growth of Ba1-xSrxZn2Si2O7 on (Ba, Sr)5(PO4)3Cl is indicated. If the surface-crystallized layer consisting of Ba1-xSrxZn2Si2O7 crystals approaches the (Ba, Sr)5(PO4)3Cl crystals in the bulk, nucleation is induced and the thus provoked growth in the same growth direction as the (Ba, Sr)5(PO4)3Cl crystal leads to a shift of the growth front towards the sample volume and hence growth-front hopping occurs.

Effect of sintering temperatures on structural and optical properties of ZnO-Zn2SiO4 composite prepared by using amorphous SiO2 nanoparticles

The effect of different sintering temperatures on structural and optical properties of ZnO-Zn2SiO4 composite was investigated. In this study, a ZnO-Zn2SiO4 composite was prepared by encapsulated zinc nitrate hexahydrate with amorphous silica nanoparticles in deionized water. The amorphous silica nanoparticles were prepared by reacting sodium silicate with ethanol. Zinc nitrate was mixed with the obtained amorphous silica nanoparticles with the ratio of 2:1 and 1.25:1 for Zn:Si and subjected to the different sintering temperatures from 600 to 1000 °C. Field emission scanning electron microscope (FESEM) microstructure showed that samples exhibit spherical morphology up to 700 °C and dumbbell morphology above 800 °C sintering temperature. The formation of Zn2SiO4 crystal phase appears from 700 °C and onwards together with ZnO crystal phase. The gaining of sintering temperature has also raised the amount of Zn2SiO4 phase and band gap values of the ZnO-Zn2SiO4 composite.

Sol-gel hot injection synthesis of ZnO nanoparticles into a porous silica matrix and reaction mechanism

Despite the enormous interest in the properties and applications of porous silica matrix, only a few attempts have been reported to deposit metal and metal oxide nanoparticles (NPs) inside the porous silica matrix. We report a simple approach (i.e. sol-gel hot injection) for insitu synthesis of ZnO NPs inside a porous silica matrix. Control of the Zn:Si molar ratio, reaction temperature, pH value, and annealing temperature permits formation of ZnO NPs (≤10nm) inside a porous silica particles, without additives or organic solvents. Results revealed that a solid state reaction inside the ZnO/SiO2 nanocomposites occurs with increasing the annealing temperature. The reaction of ZnO NPs with SiO2 matrix was insignificant up to approximately 500°C. However, ZnO NPs react strongly with the silica matrix when the nanocomposites are annealed at temperatures above 700°C. Extensive annealing of the ZnO/SiO2 nanocomposite at 900°C yields 3D structures made of 500nm rod-like, 5–7μm tube-like and 3–5μm needle-like Zn2SiO4 crystals. A possible mechanism for forming ZnO NPs inside porous silica matrix and phase transformation of the ZnO/SiO2 nanocomposites into 3D architectures of Zn2SiO4 are carefully discussed.

Synthesis and characterization of low cost willemite based glass–ceramic for opto-electronic applications

This paper presents a comprehensive study on thermal, structural and optical properties of novel willemite glass–ceramics. The precursor glass in the ZnO–SLS glass system was successfully prepared using conventional melt-quenching technique and willemite (Zn2SiO4) glass–ceramics were derived from this precursor glass by a control crystallization process. The effect of heat-treatment temperature on the phase transformation, morphology and size of Zn2SiO4 crystal phase was examined using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) techniques. Furthermore, fourier transform infrared reflection (FTIR) spectroscopy was used to evaluate the Zn2SiO4 crystal structural evolution. The average size of Zn2SiO4 crystallite obtained from calculation of XRD is found to be in the range 30–60 nm, whereas the grain size observed in FESEM is in range of 200–400 nm. The appearance of SiO2, ZnO4 and Zn–O–Si bands detected from FTIR indicate the formation of Zn2SiO4 crystal phase. Besides, the study of the optical band gap has found that optical band gap of the glass–ceramics decreased as the heat treatment temperature increased. The photoluminescence spectra of willemite glass–ceramics exhibit two different emissions around 525 nm (green) and 585 nm (yellow); exhibit a characteristic of broad absorption band around 260 nm. These two different spectra reveal that the luminescence performance of the willemite glass–ceramics was enhanced with the progression of heat treatment temperature due to different located energy levels of the β-Zn2SiO4 and α-Zn2SiO4 crystalline phase. Such luminescent glass–ceramics was expected to find potential applications in phosphors and opto-electronic devices.

Development and Characterization Studies of Eu3+-doped Zn2SiO4 Phosphors with Waste Silicate Sources

Structures, morphologies, and properties of europium doped zinc silicate were characterized using X-ray diffractometer, Field emission scanning electron microscope, Fourier transform infrared spectrometer, and UV-vis spectrophotometer. The density of doped zinc silicate shows the trend of increment when the sintering temperature increases. The XRD pattern shows that the material was highly crystalline, having sharp peaks, while the FESEM image reveals the presence of densely packed grains as sintering temperature increased 600 ̊C up to 1000 ̊C. The increase of transmission band intensities at 3443, 1630, 980, 650, 530 cm-1 confirmed the crystallization of Zn2SiO4 crystal in the glass matrix with increasing sintering temperature. Lastly, the increment of energy band gap after sintering temperature at 900 ̊C was related to the stabilization of α-Zn2SiO4 phase in material.

Influence of rare earth oxides on the non-isothermal crystallization of phosphosilicate melts during cooling

We report a detailed calorimetric study concerning the influence of Yb2O3 and Er2O3 on the non-isothermal crystallization in phosphosilicate melts. The results show that Yb3+/Er3+ ions promote the Zn2SiO4 crystal formation, but suppress the Na3PO4 and AlPO4 formation during cooling. The non-isothermal melt-crystallization kinetics can be well described by the Avrami model. The activation energy Ee of crystallization in both the undoped and Yb3+/Er3+ codoped samples during cooling is determined using the differential iso-conversional method of Friedman. The Ee value decreases with crystallinity (θ=0.1 to 0.9) during cooling for both glasses, and introducing Yb2O3 and Er2O3 leads to an increase in energy barrier of crystallization upon cooling.

Mn-Doped Zn2SiO4 Thin Film with Green Fluorescence Enhanced by Ag Nano Island Surface Plasmon Effect

20–100 nm thin films of silver were first deposited on quartz glass by magnetron sputtering. These specimens were then annealed at 500 °C for 15 min by rapid thermal annealing (RTA), which might change the silver films into having a morphology of nano islands. Subsequently, a thin film of Mn-doped ZnO was deposited on the above specimens in a sputtering system. These specimens were removed from the sputtering system and annealed again in an atmospheric furnace at 1200 °C for 2 h. By X-ray diffraction (XRD) analysis, the annealed samples were identified as Mn-doped Zn2SiO4 crystals. Furthermore, photoluminescence (PL) measurement showed the 530 nm (green light) fluorescence. The silver nano islands embedded in the Mn-doped Zn2SiO4 crystals tended to show an increase in PL intensity in the following order and in increase rate composed with their pristine Mn-doped Zn2SiO4 counterpart: 100 nm Ag (-0.33%), 50 nm Ag (-0.02%), 20 nm Ag (87.4%), 40 nm Ag (124.3%), and 30 nm Ag (168.5%). Accordingly, the plasmon effect may lead to the enhancement of fluorescence, and the size of silver nano islands determines the increase rate.

Role of sublattices in the formation of the electronic structure and chemical bonding in a Zn2SiO4 crystal with a defect chalcopyrite lattice

The effect of sublattices on the electronic structure of Zn2SiO4 crystals is ab initio studied from the first principles calculations at the density functional theory level. Based on the analysis of band spectra and sublattices the different role of Zn and Si cations in the formation of the valence band structure is determined, which is due to the crystal structure and atomic interactions in SiO4 and ZnO4 cationic tetrahedra.