Low-firing and temperature stability regulation of tri-rutile MgTa_(2)O_(6)microwave dielectric ceramics

A glass frit containing Li_(2)O-MgO-ZnO-B_(2)O_(3)-SiO_(2)component was used to explore the low-temperature sintering behaviors and microwave dielectric characteristics of tri-rutile MgTa_(2)O_(6)ceramics in this study.The good low-firing effects are presented due to the high matching relevance between Li_(2)O-MgO-ZnO-B_(2)O_(3)-SiO_(2)glass and MgTa_(2)O_(6)ceramics.The pure tri-rutile MgTa_(2)O_(6)structure remains unchanged,and high sintering compactness can also be achieved at 1150℃.We found that the Li_(2)O-MgO-ZnO-B_(2)O_(3)-SiO_(2)glass not only greatly improves the low-temperature sintering characteristics of MgTa_(2)O_(6)ceramics but also maintains a high(quality factor(Q)×resonance frequency(f))value while still improving the temperature stability.Typically,great microwave dielectric characteristics when added with 2wt%Li_(2)O-MgO-ZnO-B_(2)O_(3)-SiO_(2)glass can be achieved at 1150℃:dielectric constant,ε_(r)=26.1;Q×f=34267 GHz;temperature coefficient of resonance frequency,τ_(f)=-8.7×10^(-6)/℃.

Crystallization characteristics of iron-rich glass ceramics prepared from nickel slag and blast furnace slag

The crystallization process of iron-rich glass-ceramics prepared from the mixture of nickel slag（NS） and blast furnace slag（BFS） with a small amount of quartz sand was investigated.A modified melting method which was more energy-saving than the traditional methods was used to control the crystallization process.The results show that the iron-rich system has much lower melting temperature,glass transition temperature（Tg）,and glass crystallization temperature（Tc）,which can result in a further energy-saving process.The results also show that the system has a quick but controllable crystallization process with its peak crystallization temperature at 918°C.The crystallization of augite crystals begins from the edge of the sample and invades into the whole sample.The crystallization process can be completed in a few minutes.A distinct boundary between the crystallized part and the non-crystallized part exists during the process.In the non-crystallized part showing a black colour,some sphere-shaped augite crystals already exist in the glass matrix before samples are heated to Tc.In the crystallized part showing a khaki colour,a compact structure is formed by augite crystals.

Effect of Fe_2O_3 on the crystallization behavior of glass-ceramics produced from naturally cooled yellow phosphorus furnace slag

CaO–Al2O3–SiO2(CAS) glass-ceramics were prepared via a melting method using naturally cooled yellow phosphorus furnace slag as the main raw material. The effects of the addition of Fe2O3on the crystallization behavior and properties of the prepared glass-ceramics were studied by differential thermal analysis, X-ray diffraction, and scanning electron microscopy. The crystallization activation energy was calculated using the modified Johnson–Mehl–Avrami equation. The results show that the intrinsic nucleating agent in the yellow phosphorus furnace slag could effectively promote the crystallization of CAS. The crystallization activation energy first increased and then decreased with increasing amount of added Fe2O3. At 4wt% of added Fe2O3, the crystallization activation energy reached a maximum of 676.374 kJ·mol−1. The type of the main crystalline phase did not change with the amount of added Fe2O3. The primary and secondary crystalline phases were identified as wollastonite (CaSiO3) and hedenbergite (CaFe(Si2O6)), respectively. © 2017, University of Science and Technology Beijing and Springer-Verlag Berlin Heidelberg.

THE STRUCTURE AND PROPERTIES OF Li_2O-Al_2O_3-SiO_2LOW EXPANSION GLASS CERAMICS CONTAINING B_2O_3

Through measuring the coefficient of linear expansion, the structure and properties of the Li2O-Al2O3-SiO2 low expansion glass ceramics containing B2O3 are studied by JR and XRD. It is shoutn that the IR method is efficient in the study of the glass-ceramics structure. There is a " Boron abnormality" in the system which has an important influence on the properties of the glass-ceramics.

Optical temperature sensor based on up-conversion fluorescence emission in Yb^(3+):Er^(3+) co-doped ceramics glass

yb^3＋：Er^3＋ co-doped oxy-fluoride ceramics glass has been prepared. The mechanism of up-conversion emissions about Er^3＋ was discussed, and the temperature properties of green up-conversion fluorescence between 303 and 823 K were investigated. The results show that the sensitivity of this sample reaches its maximum value, about 0.0047 K^-1, when the temperature is 383 K, indicating that this kind of sample can be used as high temperature and high sensitivity optical temperature sensor.

Effects of ZnO,FeO and Fe_(2)O_(3)on the spinel formation,microstructure and physicochemical properties of augite-based glass ceramics

Augite-based glass ceramics were synthesised using ZnO,FeO,and Fe_(2)O_(3)as additives,and the spinel formation,matrix structure,crystallisation thermodynamics,and physicochemical properties were investigated.The results showed that oxides resulted in numerous preliminary spinels in the glass matrix.FeO,ZnO,and Fe_(2)O_(3)influenced the formation of spinel,while FeO simplified the glass network.FeO and ZnO promoted bulk crystallisation of the parent glass.After adding oxides,the grains of augite phase were refined,and the relative quantities of augite crystal planes were also influenced.All samples displayed good mechanical properties and chemical stability.The 2wt%ZnO-doping sample displayed the maximum flexural strength(170.3 MPa).Chromium leaching amount values of all the samples were less than the national standard(1.5 mg/L),confirming the safety of the materials.In conclusion,an appropriate amount of zinc-containing raw material is beneficial for the preparation of augite-based glass ceramics.

Study on crystallization and microstructure of Li_2O-Al_2O_3-SiO_2 glass ceramics

Lithium aluminosilicate （LAS） glasses are generally difficult to prepare because of their high melting temperature. In this study, the preparation of LAS glasses was achieved at a relatively low melting temperature. The batch containing MgO-ZnO-LiEO- Al2O3-SiO2 was melted in a platinum crucible at 1550℃ for 2 h and was then followed by two- or three-step heat treatment processes for nucleation and crystal growth. The characterizations were carried out by differential thermal analysis, X-ray diffraction, infrared spectroscopy, scanning electron microscopy, and UV-Vis-NIR scanning spectrophotometry. The hexagonal stuffed β-eucryptite solid solution crystallized at 840-960℃. Most of the hexagonal β-eucryptite solid solution transformed into the tetragonal β-spodumene solid solution at 1100℃. Almost all the aluminum atoms entered into the tetrahedral sites in the aluminosilicate network of the 6- eucryptite/β-quartz solid solution. All of the Al atoms did not belong to the aluminosilicate network of the β-spodumene solid solution. The glass ceramic with a mean grain size of 10-20 nm is transparent, the transmittance reaches -85% in the visible light wavelength.

Sintering Behavior and Microwave Dielectric Properties of BBSZL Glass-doped ZnTiO_3 Ceramics for LTCC Applications

A novel low temperature co-fired ceramic(LTCC) material was fabricated by zinc titanate(ZnTiO_3) ceramics doped with B_2O_3-BaO-SiO_2-ZnO-Li_2O(BBSZL) glass. The influences of BBSZL glass on wetting behavior, sintering activation energy, phase composition, microstructure and microwave dielectric properties were investigated. The experimental results show that the sintering temperature of ZnTiO3 ceramics can be reduced from 1 100 to 925 ℃, meanwhile the sintering activation energy is decreased from 465.32 to 390.54 kJ·mol^(-1) by BBSZL glass aid, respectively. Moreover, BBSZL glass can inhibit the high Q×f ZnTiO_3 phase decompose into the low Q×f value Zn_2TiO_4 phase, which is propitious to obtain high Q×f value LTCC material. The ZnTiO_3-BBSZL composite sintered at 925℃ displays the excellent microwave dielectric properties with ε_r of 21.8, Q×f value of 42000 GHz, and τ_f of-75 ppm·℃^(-1).

Spectroscopic properties and mechanism of Tm^(3+)/Er^(3+)/Yb^(3+) co-doped oxyfluorogermanate glass ceramics containing BaF_2 nanocrystals

Transparent Tm^3＋/Er^3＋/yb^3＋ co-doped oxyfluorogermanate glass ceramics containing BaF2 nanocrystals are prepared. Under excitation of a 980-nm laser diode （LD）, compared with the glass before heat treatment, the Tm^3＋/Er^3＋/yb^3＋ co-doped oxyfluorogermanate glass ceramics can emit intense blue, green and red up-conversion luminescence and Stark- split peaks; X-ray diffraction （XRD） and transmission electron microscope （TEM） results show that BaF2 nanocrystals with an average diameter of 20 nm are precipitated from the glass matrix. Stark splitting of the up-conversion luminescence peaks in the glass ceramics indicates that Tm^3＋, Er^3＋ and （or） Yb^3＋ ions are incorporated into the BaF2 nanocrystals. The up-conversion luminescence intensities of Tm^3＋, Er^3＋ and the splitting degree of luminescence peaks in the glass ceramics increase significantly with the increase of heat treat temperature and heat treat time extension. In addition, the possible energy transfer process between rare earth ions and the up-conversion luminescence mechanism are also proposed.

Sintering,crystallization and dielectric properties of CaO-B_2O_3-SiO_2 system glass ceramics

CaO-B203-SiO2 （CBS） glass powders are prepared by conventional glass melting method at different melting temperatures whose properties and microstructures are characterized by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. It is found that there are SiO2 and some unknown phases in CBS glass melting liquid from 1 300 ℃ to 1 500 ℃ and the amount of these phases decreases with the increase of the melting temperature. The CBS glass melted at 1 450 ℃ could be sintered from 830 ℃ to 930 ℃ and the bulk densities of the samples are all higher than 2.4 g/cm^3. From the points of the properties and energy conservation, the melting temperature of 1 450 ℃ is the optimal melting temperature. The glass ceramic sintered at 850 ℃ exhibits better dielectric properties： er=6.33, tan6=2.2×10^-3 at 10 GHz, and the major phases of the samples are CaSiO3, CaB2O4 and SiO2.

Effect of the Fourth Element on Bonding of Silicon Nitride Ceramics with Y_2O_3-Al_2O_3-SiO_2 Glass Solders

Bonding of Si 3N 4 ceramic was performed with Y 2O 3 Al 2O 3 SiO 2(YAS) X glass solders,which were mixed with TiO 2 (YT) and Si 3N 4 (YN), respectively. The effects of bonding conditions and interfacial reaction on the joint strength were studied. The joint strength in different bonding conditions was measured by four point bending tests. The interfacial microstructures were observed and analyzed by SEM, EPMA and XRD. It is shown that with the increase of bonding temperature and holding time, the joint strength increases reaching a peak, and then decreases. When TiO 2 is put into YAS solder,the bonding interface with Si 3N 4/(Y Sialon glass+TiN)/TiN/Y Sialon glass is formed. When YAS solder is mixed with Si 3N 4 powder, the interfacial residual thermal stress may be decreased, and then the joint strength is enhanced. According to microanalyses, the bonding strength is related to interfacial reaction.

Near-infrared Quantum Cutting in Pr^(3+)-Yb^(3+) Co-doped Oxyfluoride Glass Ceramics Containing CaF_2 Nanocrystals

The Pr3＋-Yb3＋ co-doped oxyfluoride glass-ceramics containing CaF2 nanocrystals were obtained by thermal treatment on the as-made glasses. The structure of fluoride nanocrystals was investigated. The light-emitting mechanism of pr3＋-yb3＋ in the near infrared region was proposed and the fluorescence lifetime and quantum efficiency was calculated. The results indicate that the main phase in the oxyfluoride glass- ceramics is CaF2 nanocrystal sized at 30 nm. Energy dispersive spectroscopy （EDS） and X-ray diffraction （XRD） have proved the incorporation of Pr3＋ and Yb3＋ into CaF2 nanocrystal lattice, Near-infrared quantum cutting involving Yb3＋ 980 nm and 1 015 tun （2F5/2→2F7/2） emission has been achieved upon the excitation of the 3P0 energy level of Pr3＋ at 482 nm. The fluorescence lifetime decreases sharply and quantum efficiency increases with increasing Yb3＋ concentration, and the optimal quantum efficiency reaches 191%.

Effect of sintering temperature on the microstructure and properties of foamed glass-ceramics prepared from high-titanium blast furnace slag and waste glass

Foamed glass-ceramics were prepared via a single-step sintering method using high-titanium blast furnace slag and waste glass as the main raw materials The influence of sintering temperature(900–1060℃) on the microstructure and properties of foamed glass-ceramics was studied. The results show that the crystal shape changed from grainy to rod-shaped and finally turned to multiple shapes as the sintering temperature was increased from 900 to 1060℃. With increasing sintering temperature, the average pore size of the foamed glass-ceramics increased and subsequently decreased. By contrast, the compressive strength and the bulk density decreased and subsequently increased. An excessively high temperature, however, induced the coalescence of pores and decreased the compressive strength. The optimal properties, including the highest compressive strength(16.64 MPa) among the investigated samples and a relatively low bulk density(0.83 g/cm^3), were attained in the case of the foamed glass-ceramics sintered at 1000℃.

Luminescence of Er^(3+) in Oxyfluoride Transparent Glass-Ceramics

Erbium doped silicate, germanate, and tellurium-germanate oxyfluoride glasses were prepared in a bulk form. Through appropriate heat treatment of the as-prepared glasses, transparent glass-ceramics （TGCs） were obtained with the formation of β-PbF2：Er^3＋ nanocrystals in the glass matrix were confirmed by X-ray diffraction.Well-defined diffraction peaks were observed in the samples after heat-treatment. The average crystal diameter of these precipitated crystals from full-width at half-maximum （FWHM） of the diffraction peak was estimated to be between 8 and 13 nm. Optical absorption, photoluminescence, and upconversion luminescence were measured on as-prepared glass and glass-ceramics. Luminescence spectra in the TGC samples revealed well-resolved, sharp stark-splitting peaks, which indicates that a majority of Er^3＋ ions has been incorporated into the crystalline phase of the nanocrystals. The intensity of the visible and near infrared luminescence mostly increases in TSG compared to that in the as-prepared glass. In 1.53 μm absorption and emission bands, the maximum absorption peak is blue-shifted from 1531 to 1507 nm, whereas the maximum emission peak is redshifted from 1535 to 1543 nm in TGC, as compared with that in glass. The bandwidth at half-maximum （BWHM） of the emission band is significantly broader in TGC than in glass, which is beneficial to the erbium-doped fiber amplifier （EDFA）. Upconversion luminescence was measured using 800 nm near-infrared light excitation. Drastically increased upconversion 1 was observed from the TGC as compared to that from their corresponding as-prepared glasses. In addition to a strong green emission centered at 545 nm because of ^4S3/2→^4I15/2 transition and a weaker red emission centered at 662 nm because of ^4F9/2→^4I15/2 transition, generally seen from the Er^3＋ doped glasses, two violet emissions centered at 410 nm because of ^2H9/2→^4I15/2 transition and centered at 379 nm because of ^4G11/2→^4I15/2 transition were also observed from the was attributed to the decreased effective phonon energy and the increased energy transfer between the excited ions when Er^3＋ ions were incorporated into the precipitated β-PbF2 nanocrystals. The results indicated two attractive spectroscopic properties of the Er^3＋ doped TGC samples, compared to glass samples, namely a reduced multiphonon decay rate and a reduced inhomogeneous broadening. In addition, these oxyfluoride TGC materials were robust,easy and flexibile to process, and possible to be fabricated in the fiber form for device applications.

Nucleation and crystallization of tailing-based glass-ceramics by microwave heating

The effect of microwave radiation on the nucleation and crystallization of tailing-based glass-ceramics was investigated using a 2.45 GHz multimode microwave cavity. Tailing-based glass samples were prepared fi＇om Shandong gold tailings and Guyang iron tailings utilizing a conventional glass melting technique. For comparison, the tailing-based glass samples were crystallized using two different heat-treatment methods： conventional heating and hybrid microwave heating. The nucleation and crystallization temperatures were determined by performing a differential thermal analysis of the quenched tailing-based glass. The prepared glass-ceramic samples were further characterized by Fourier transform infrared spectroscopy, X-ray diffraction, Raman spectroscopy, thermal expansion coefficient measurements, and scanning electron microscopy. The results demonstrated that hybrid microwave heating could be successfully used to crystallize the tailing-based glass, reduce the processing time, and decrease the crystallization temperature. Furthermore, the results indicated that the nucleation and crystallization mechanism of the hybrid microwave heating process slightly differs fi＇om that of the conventional heating process.

Influence of aluminium nitride as a foaming agent on the preparation of foam glass-ceramics from high-titanium blast furnace slag

To effectively reuse high-titanium blast furnace slag （TS）, foam glass-ceramics were successfully prepared by powder sintering at 1000℃. TS and waste glass were used as the main raw materials, aluminium nitride （AIN） as the foaming agent, and borax as the fluxing agent. The influence of the amount of A1N added （lwt%-5wt%） on the crystalline phases, microstructure, and properties of the produced foam glass-ceramics was studied. The results showed that the main crystal phases were perovskite, diopside, and augite. With increasing A1N content, a transformation from diopside to augite occurred and the crystallinity of the pyroxene phases slightly decreased. Initially, the aver- age pore size and porosity of the foam glass-ceramics increased and subsequently decreased; similarly, their bulk density and compressive strength decreased and subsequently increased. The optimal properties were obtained when the foam glass-ceramics were prepared by adding 4wt% AIN.

Development of Modified Glasses by Transparent, Functional Hybrid Sol-Gel Nano-Ceramic Coatings, a Comparative Study

This paper concentrates on the development of glasses with self-cleaning surfaces exhibiting high water contact angles. In this study, we prepared super-hydrophobic nano-ceramic coated glass based on titania & silica using simple sol-gel & dip coating methods and studied the best composition of the coatings by altering ratios of titanium tetraisopropoxide (TTIP)/tetraethyl orthosilicate (TEOS) with different homogenizing agents. We characterized the coatings by surface roughness measurement, percentage of optical transmission, static contact angle, near-infrared (NIR) transmission, and diffuse reflectance. The fabrication of coatings on glass substrates played an important role in increasing the water contact angle of about 95° and visible & NIR transmission of about 90%. We compared our modified glass substrate with commercial low emissivity (Low E) glass using X-ray diffraction (XRD) analysis, which showed pure amorphous surface claiming excellent wettability and thus the prepared glass substrate could have a variety of applications in different fields.

Preparation,crystallization,and wetting of ZnO-Al_2O_3-B_2O_3-SiO_2 glass-ceramics for sealing to Kovar

A novel type of ZnO-Al2O3-B2O3-SiO2 glass-ceramics sealing to Kovar in electronic packaging was developed, whose thermal expansion coefficient and electrical resistance are 5.2× 10^-6/℃ and over 1×10^13 Ω·cm, respectively. The major crystalline phases in the glass-ceramic seals were ZnAl2O4, ZnB2O4, and NaSiAl2O4. The dielectric resistance of the glass-ceramic could be remarkably enhanced through the control of alkali metal ions into crystal lattices. It was found that crystallization happened first on the surface of the sample, leaving the amorphous phase in the inner, which made the glass suitable for sealing. The glass-ceramic showed better wetting on the Kovar surface, and sealing atmosphere and temperature had great effect on the wetting angle. Strong interracial bonding was obtained, which was mainly attributed to the interracial reaction between SiO2 and FeO or Fe3O4.

Effect of Nucleating Agents and Heat Treatments on the Crystallization of Magnesium Aluminosilicate Transparent Glass-ceramics

The crystallization behavior and transparent property of MgO-A1203-SiO2 （MAS） glasses with TiO2 and TiO2＋ZrO2 as nucleating agents were discussed by differential thermal analysis, X-ray diffraction, field emission-environment scanning electron microscope, energy dispersive spectrum and UV-VIS-NIR scanning spectrophotometer. It was found that the glass crystallized at 950 ℃ with ZrO2 less than 3% could obtain transparent glass ceramic, which presented purple to colorless. With the nucleating agent additives （5% TIO2＋3% ZrO2）, the colorless transparent glass-ceramics with spinel as the main crystal phase could be prepared, and the transmittance reached about 80%. As the crystallized temperature increase to 1 000 ℃, besides spinel（MgA1204）, sapphirine （Mg3.5A19Si1.5O20） and ZrTiO4 precipitated from matrix glass, and the transmitance of glass-ceramic decreased.

Effect of Water Washing Pre-treatment on the Properties of Glass-ceramics from Incinerator Fly Ash Using Electronic Arc Furnace

Production of glass-ceramics by sintering the molten slag obtained from electric arc furnace treatment of fly ash was investigated. The effect of washing pretreatment prior to melting the fly ash on the microstructure and properties of the glass-ceramics was examined. The results show that washing pretreatment of fly ash can decrease alkali metal chloride and increase network former in fly ash, which results in the increase of peak crystallization temperature of parent glass and strengthening of properties of bending strength and chemical stability of the glass-ceramics. The optimal heat treatment temperature for parent glass of washed fly ash is 1 173 K, at which the crystalline phase of glass-ceramics is composed of gelignite （Ca2A12SiO7） and akermanite （Ca2MgSi207）. Glass-ceramics produced at optimal heat treatment temperature are excellent in term of the physical and chemical properties and leaching characteristics, indicating attractive potential as substitute of nature materials.