Cordierite-based Glass-ceramics Research Articles

Development of cordierite-based glass-ceramics by slip casting through selecting the appropriate sintering conditions

The present work aims to prepare a dense cordierite-based glass-ceramic through slip casting and consequent heat treatment procedures. In this regard, sintering conditions were considered as the key variables to improve the properties of the glass-ceramic. For this purpose, glass frit powder was prepared through melting oxide powders (in the system of SiO2-Al2O3-TiO2-K2O-CaO-MgO). The mixed powders were then heat treated at 1450 °C for 1 hour and quenched in water. The glass frit powder was slip cast using the appropriate dispersant. Sintering was carried out by one-step, two-step, and three-step procedures. Specimens were characterized in terms of various analysis techniques including dilatometry, X-ray diffractometry, scanning electron microscopy, and mechanical strength measurement. Among the examined specimens, the sample sintered by a three-step approach was considered the optimized one which attained zero porosity. According to the obtained results, cordierite crystals were observable in this glass-ceramic matrix. A low coefficient of thermal expansion and a low dielectric constant were observed for the optimized glass-ceramic sample. The obtained results confirmed that the homogenous distributions of crystalline phases are responsible for the appropriate and desirable properties of the prepared glass-ceramic.

Effects of BaO on crystallization, structure and dielectric properties of MgO–Al2O3–SiO2 glass–ceramics for LTCC applications

Cordierite-based glass–ceramics for LTCC applications were prepared by traditional sintering method. And the effects of BaO addition on the crystallization, structure and dielectric properties were investigated by differential scanning calorimetry (DSC), scanning electron microscopy (SEM), X-ray diffractometer (XRD), dilatometer and impedance instrument. The DSC curves displayed that the glass transition temperature (Tg) slowly decreased with the BaO content increasing from 0 to 4 mol%. However, the onset of crystallization temperature (Tx) and crystallization peak temperature (Tc) showed the opposite trend. XRD analysis revealed that μ-cordierite was the major crystal phase for all the glass–ceramic samples, while α-cordierite precipitated as the minor crystal phase with BaO addition. As more BaO was added, the bulk density gradually increased, while the porosity decreased, indicating that BaO improved the sinterability of the glass samples. The dielectric constant showed minimum value with the addition of 2 mol% BaO, and the dielectric loss reached the minimum value when the content of BaO was 3 mol%. Wherein, after heated at 950 °C, glass–ceramics doped with 2 mol% BaO showed a dense structure, a relatively low dielectric constant (4.53), a low dielectric loss (2 × 10−3) at 1 MHz, and a proper CTE value (3.74 × 10–6/°C), which can be used to prepare LTCC materials.

Effect of MgO/SiO2 ratio and Al2O3 content on crystallization behavior and properties of cordierite-based glass–ceramics

Cordierite-based glass-ceramics with non-stoichiometric compositions were prepared by powder sintering method. The effects of MgO/SiO2 ratio and Al2O3 content on the crystallization behavior, microstructure and thermal expansion coefficient of the glass-ceramics were studied. Results indicated that the decreasing Al2O3 content showed a greater effect on decreasing the melting temperature and liquid viscosity than the increasing MgO/SiO2. DTA results showed that, at low temperatures, the MgO/SiO2 ratio dominated crystallization of cordierite due to the lack of liquid. At a high sintering temperature of 1340 °C, the Al2O3 content dominated the crystal growth of cordierite due to its great effect on decreasing the liquid viscosity. The chemical composition close to the stoichiometric cordierite and the absence of quartz were two essential factors for obtaining low thermal expansion coefficients. The decreasing MgO/SiO2 ratio and Al2O3 content caused phase separation with an interconnected structure, which followed the crystallization of cordierite in the Al2O3-rich phase.

The Effects of Co2O3 Addition on Crystallization, Microstructure and Properties of Cordierite-Based Glass-Ceramics

The Co2O3 doped MgO-Al2O3-SiO2-B2O3 (MASB) glass-ceramics were successfully fabricated by traditional melt quenching method and the following heat treatment. The effect of Co2O3 addition on crystallization behavior, glass networks, microstructure and physical properties was investigated by differential scanning calorimetry (DSC), X-ray diffraction (XRD), Fourier transform infrared absorption spectra (FTIR) and scanning electron microscopy (SEM) measurements. The results show that the metastable phase μ-cordierite and α-cordierite precipitated from the parent glass during the thermal treatment process. With the increase of Co2O3 content, the crystallization tendency of the parent glass increased, and the addition Co2O3 favored the transformation from μ-cordierite to α-cordierite. Meanwhile, the grain size of glass-ceramics increased obviously, Simultaneously, the mechanical strength of glass-ceramics increased first and then decreased, while the thermal expansion coefficient decreased. Glass-ceramic with excellent thermal and physical properties were prepared by adding 0.1 mol% Co2O3 content and then crystallizing it at 1020 ∘C for 3 h.

Effects of alkali metal oxides on crystallization behavior and acid corrosion resistance of cordierite-based glass-ceramics

MgO-Al2O3-SiO2-TiO2 glass-ceramics with 3mol% alkali metal oxides were prepared, and the 3mol% alkali metal oxides were induced by 3mol% Na2O only, 1.5mol% Na2O+1.5mol% Li2O, and 1.5mol% Na2O+1.5mol% K2O, respectively. Effects of alkali metal oxides on the crystallization behavior and acid corrosion resistance of the MgO-Al2O3-SiO2-TiO2 glass-ceramics were investigated. The results showed that μ-cordierite precipitated in the glass matrix firstly, and it changed into α-cordierite with the crystallization temperature increasing. Using K2O substitution of Na2O hindered the precipitation of cordierite, while the addition of Li2O promoted the precipitation of μ-cordierite at low temperatures. When the main crystalline phase was μ-cordierite, the acid resistance of the glass-ceramics was significantly improved compared with the base glass. With the main crystalline phase changing from μ-cordierite to α-cordierite, the acid resistance of the glass-ceramics became worse, which was related to the honeycomb structure of α-cordierite. When 1.5mol% Na2O was replaced by Li2O, the glass samples crystallized at 880°C showed the optimum acid resistance with the minimum weight loss ~0.096%.

Dependence of Crystallization Behavior and Microstructural Change in Cordierite-Based Glass-Ceramics upon Acid-Etching on Glass Frit

Dependence of Crystallization Behavior and Microstructural Change in Cordierite-Based Glass-Ceramics upon Acid-Etching on Glass Frit

Crystallization kinetic and thermal and electrical properties of β-spodumeness/cordierite glass–ceramics

The aim of the present work was to investigate the crystallization kinetic of spodumene-/cordierite-based glass–ceramics. Thus, three glasses were prepared with compositions based predominantly on cordierite and β-spodumeness crystalline phases, and a mass ratio 1:1 of both phases. The kinetic parameters were determined by means of non-isothermal methods using differential thermal analysis. A multi-peaks fit method was used based on the Fraser–Suzuki equation to determine the crystallization temperature peak. The crystallization kinetic was investigated using the Ozawa and Kissinger methods. The samples were crystalized according to DTA analyses and characterized by using X-ray diffraction. Additionally, the coefficient of thermal expansion and electrical properties of the glass–ceramics was determined. The results showed activation energy for crystallization ranging from 121 to 333 kJ mol−1. The main crystalline phases were β-spodumeness to composition L, cordierite and β-quartzss to composition C and β-quartzss and spinel to composition CL. Taking into account the thermal and electrical properties of the heat-treated samples, these glass–ceramics show potential to LTCC (low thermal co-fired ceramics) application.

Effect of replacement of B2O3 by ZnO on preparation and properties of transparent cordierite-based glass-ceramics

The effect of B2O3 replacement by different contents of ZnO on the preparation and various properties of transparent cordierite-based glass-ceramics was deeply investigated. With ZnO addition, the glass transition temperature (Tg) changed slightly, while the crystallization temperature (Tc) decreased greatly, which was confirmed by the DSC results. According to the X-ray diffraction and TEM analysis, ZnO affected the type of the crystal phases, as well as increased the crystallinity and changed the grain size. In addition, the transmittance, thermal expansion coefficient, Vickers hardness and bending strength of glass-ceramics were greatly influenced by the content of ZnO. Transparent glass-ceramics with excellent optical, thermal and physical properties were prepared by nucleating the sample with 2mol% ZnO content at 820°C for 6h and then crystallizing it at 1000°C for 6h.

Preparation and properties of transparent cordierite-based glass-ceramics with high crystallinity

Transparent cordierite-based glass-ceramics with high crystallinity were prepared successfully. The crystallization kinetics of parent glass was deeply investigated by differential scanning calorimetry (DSC). After heat-treatment at 1030°C for 6h, a large amount of α-cordierite (indialite) crystals devitrified from the parent glass, which was confirmed by the X-ray diffraction and TEM results. The crystallinity of the obtained transparent glass-ceramics reached up to 87.5%, which can be ascribed to the composition and heat treatment of parent glass. The high transparency of glass-ceramics mainly resulted from the small difference of refractive index between α-cordierite and the parent glass. In addition, these transparent glass-ceramics possessed low density (2.477g/cm3), low thermal expansion coefficient (1.435×10−6°C−1) and high Vickers hardness (8.1GPa). The combination of excellent physical, thermal and optical properties makes this new family of transparent glass-ceramics exhibiting potential applications in the fields of base materials for rare-earth ions.

Novel cordierite nanopowders of new crystallization aspects and its cordierite-based glass ceramics of improved mechanical and electrical properties for optimal use in multidisciplinary scopes

Nanocrystalline α-cordierite Mg2Al4Si5O18 powders have been synthesized via a novel and facile co-precipitation method using MgCl2.6H2O, NaAlO2, Na2SiO3.5H2O as starting materials. XRD, SEM, HR-TEM and EDS techniques were employed to investigate the phase structure and crystal morphology of the synthesized powders at various annealing temperatures. The kinetics of cordierite crystallization was studied under non-isothermal conditions using Differential Thermal Analysis (DTA). The apparent activation energy (Ea) of μ-cordierite crystallization, calculated by modified Kissinger model was equal 286.1 K J mol−1 and comparable with the literature. The dielectric measurements revealed that the cordierite ceramic samples sintered at 1300 and 1350 °C could be successfully applied for electronic packaging under the microwave and radiowave frequency regions, respectively.

Low-Temperature Combustion Synthesis of Cordierite Powder and its Characteristic

The MgO-Al2O3-SiO2 (MAS) glass powders have been synthesized by low-temperature combustion technique using magnesium nitrate, aluminium nitrate, silicic acid as material, urea as fuel. The crystallization process, sintering behavior and dielectric properties were investigated by means of DTA, XRD, TMA and SEM techniques. The results showed that the glass powders could be sintered at lower than 1000°C. The μ-cordierite phase was first crystallized from glass and then transformed into α-cordierite phase during sintering process. The obtained cordierite-based glass-ceramics at 950°C and 1000°C have low dielectric constant (4.00 ~ 4.96 at 1 MHz), low dielectric dissipation factor (≈ 0.003) and high sintering density (which is above 98% of the theoretical density), which are used for electronic packaging.

Testing and Evaluation of Infrared Radiation Property of Cordierite Based Glass-Ceramic Materials

In this article we present the testing, evaluation of infrared radiation properties of polycrystalline materials especially as cordierite-based glass-ceramics. Researches aim to make a comprehensive and systematic exposition of emissivity definition, test principles and test methods. And on the basis of measurement results of the infrared emissivity of cordierite-based glass-ceramics, the Infrared radiation property of this polycrystalline material was discussed. Research has a positive significance on the development of the infrared radiation heating and drying materials.

Effects of Fe on Crystallization and Properties of a New High Infrared Radiance Glass-Ceramics

In our earlier work, a promising new approach of fly ash utilization as converting it into a high infrared radiance glass-ceramic material was proposed. In this paper, pure reagents glass-ceramics were synthesized simulating the previously obtained high infrared radiance fly ash glass-ceramics, and mechanisms of the effects of iron oxide impurity, contained in fly ash, on crystallization behavior, infrared radiation and thermal expansion properties of this material are systematically analyzed. It was originally found that the iron oxide impurity has a significant influence on the crystallization of the MgO-Al(2)O(3)-SiO(2) system glass-ceramics as it leads to phase separation of this magnesium aluminosilicate glass, and consequently results in changes of the crystallization activation energy and crystallization mechanism. Furthermore, the Fe ion is incorporated into the cordierite crystal structure in the form of Fe(3+)/Fe(2+) that coexists during crystallization, and the substitution of Mg(2+) by Fe(3+) forms the vacant site of Mg(2+) cations. For the effects of impurity, vacancy defects, and lattice distortion, which are caused by the doping of Fe ion, the infrared radiation performance of this cordierite-based glass-ceramic can be improved considerably. By controlling the iron oxide amount (about 4.2%) in this system glass-ceramics, well crystallized (bulk crystallization, granular equiaxed grains, sized 200-400 nm) Fe(3+)/Fe(2+) substituted cordierite-based glass-ceramics with excellent infrared radiation property and low thermal expansion coefficient were obtained. Since high Fe content fly ashes can be used as raw material for the synthesis of this material, the research has both ecological and economic importance.

Effect of P2O5 on evolution of microstructure of MgO–Al2O3–SiO2 glass ceramics

MgO–Al2O3–SiO2 (MAS) cordierite based glass ceramics were prepared by volume crystallisation. X-ray diffraction, Scanning electron microscopy and Energy diffraction scanning were used to investigate crystallisation behaviour and the influence of P2O5 on microstructure MAS based glass ceramics. The results showed that P5+ could promote the phase separation of MAS glass and that the glass was divided into two areas, such as Mg4Al2Ti9O25 and the containing P5+ area at <900°C. Mg4Al2Ti9O25 and Mg3(PO4)2 in the area were both advantageous to the precipitation of μ cordierite, which further transformed to α cordierite due to P5+ in the residual glassy phase. However, P5+ inhibited the presence of cordierite when the heat treatment temperature was >900°C.

Synthesis of Cordierite Powders by Low Temperature Combustion Method

The cordierite powders have been synthesized by low temperature combustion technique using urea as fuel, nitrates as oxidizer and silicic acid as silica source. The sintering behavior and crystallization process were investigated. The results showed that the powders could be sintered at a temperature lower than 1000 °C. The μ-cordierite crystallized from glass at first, and then transformed into α-cordierite at higher temperature. The obtained cordierite based glass ceramics at different temperatures have low dielectric constant (4.16 ~ 5.02 at 1 MHz) and low dielectric dissipation factor (≈ 0.003 at 1 MHz) as well as low temperature sintering behavior, which is compatible for electronic packaging.

Effect of ZnO addition on properties of cordierite-based glass-ceramics

The influences of addition of ZnO on sintering, crystallization behavior and properties of cordierite-based glass-ceramics were investigated. Results show that with increasing ZnO content, the batch melting temperature, glass transition temperature and crystallization temperature all decrease. Addition of ZnO can greatly improve the sinterability of the glass powders and alter the type of the crystalline phases. Addition of 1.5 wt% ZnO seems to be reasonable. Thermal expansion coefficients (TCEs) of samples increase with increasing ZnO contents. The density was found to be an important factor affecting the dielectric loss of the samples. Dielectric constant and TCEs of the sintered bulk samples were found to depend on their relative densities and crystalline phases. The samples doped with 1.5–3.0 wt% ZnO sintered at 950 °C has a low dielectric constant (5.0–5.2), a low dielectric loss (≤0.0018) and a low thermal expansion coefficient (3.6–4.8 × 10−6 K−1), which are promising electronic packaging materials.

Sintering, crystallization, and properties of CaO doped cordierite-based glass–ceramics

The effects of replacement of MgO by CaO on the sintering, and crystallization behavior of MgO–Al 2O 3–SiO 2 system glass–ceramics were investigated. The results show that with increasing CaO content, the glass transition temperature ( T g) firstly increased, and then decreased. The melting temperature was lowered, and the crystallization temperature of the glass–ceramics shifted clearly towards higher temperatures. With the replacement of MgO by less than 3 wt% CaO, the predominant crystalline phase in the glass–ceramics, fired at 900 °C, was found to be α-cordierite, and the secondary crystalline phase to be μ-cordierite. When the replacement was increased to 10 wt%, the predominant crystalline phase was found to be anorthite, and the secondary phase to be α-cordierite. Both the thermal expansion coefficient (TCE), and the dielectric constant of the samples increase by replacing MgO by CaO. The dielectric loss of the sample with 5 wt% CaO (C5), fired at 900 °C, has the lowest value of 0.08%. Only the sample C5 and the sample containing 10 wt% CaO, (C10), can be fully sintered before 900 °C. Therefore, a dense, and low dielectric loss glass–ceramic with predominant crystal phase of α-cordierite, and some amount of anorthite was achieved by using fine glass powders ( D 50 = 3 μm), fired at 875–900 °C. The as-sintered density approaches 98% theoretical density. The flexural strength of sample C5 firstly increases, and then decreases with sintering temperature, which closely corresponds to its relative density. The TCE of sample C5 increases with increasing temperature. The dielectric property of sample C5 sintered at different temperatures depends not only on its relative density, but also on its crystalline phases. The dense, and crystallized glass–ceramic C5 exhibits a low sintering temperature (≤900 °C), a fairly low dielectric constant (5.2–5.3), a low dielectric loss (≤10 −3) at 1 MHz, a low TCE (4.0–4.25 × 10 −6 K −1), very close to that of Si (∼3.5 × 10 −6 K −1), and a higher flexural strength (≥134 MPa), suggesting that it would be a promising material in the electronic packaging field.

Aqueous tape casting processing of low dielectric constant cordierite-based glass-ceramics—selection of binder

In this paper, four different binders were investigated in the process of aqueous tape casting of cordierite-based glass-ceramics and their effects on the rheological behaviour of the suspensions and on the microstructures of the green tapes were compared. Meanwhile, a good compatibility between the dispersant and binder was found to be a predominant factor to obtain an optimised cordierite glass-ceramic tape. The microstructure of the green tape was observed by SEM and the weight loss during binder burn out process was determined by DTA/TG. The dielectric constant and dielectric loss of the sintered tapes (at 1150 °C for 2 h) was also measured.

Synthesis, Characterization, and Processing of Cordierite-Glass Particles Modified by Coating with an Alumina Precursor

The surfaces of cordierite and glass particles were modified by coating them with an alumina precursor using a precipitation process in the presence of urea. Scanning electron microscopy (SEM), high-resolution transmission electron microscopy, X-ray diffraction, electrophoresis, and rheological measurements were used to characterize the coated powders. SEM and transmission electron microscopy morphologies of the coated powders revealed that amorphous and homogeneous coatings have been formed around the particles. The morphology of the coated powders showed a coiled wormlike surface. The coating Al2O3 layer dominated the surface properties of the coated glass and cordierite powders. The influence of the coating layer on the processing ability of cordierite-based glass-ceramics substrates by tape casting was studied in aqueous media. It could be concluded that the coating of the powders facilitates the processing and yields green and sintered tapes with denser, more homogeneous microstructures compared with the uncoated powders.

Production and properties of cordierite-based glass-ceramics from gold tailings

Cordierite-based glass-ceramics have been developed using gold tailings as one of the starting raw materials. The crystallization behaviour of gold tailings based glass samples was investigated by DTA, XRD, and SEM. On the basis of DTA analysis, nucleation experiments were carried out at 820 °C for 2 h and crystallization experiments were performed at 1010 °C for 2 h. X-ray diffraction analysis revealed that the major phase of the synthesized glass-ceramics was cordierite along with a trace of iron cordierite. The properties of the synthesized cordierite-based glass-ceramics compared well with the values of industrial cordierite. Results indicate an interesting potential for gold tailings to produce useful materials.