Enhanced Sinterability, Thermal Conductivity and Dielectric Constant of Glass-Ceramics with PVA and BN Additions (original) (raw)
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Structural, electrical and thermal properties of borosilicate glass–alumina composites
Borosilicate glass–alumina composites with (1 À x) Glass + x Al 2 O 3 (x = 0, 5, 10, 25 vol.%) were prepared and the effect of Al 2 O 3 addition on the structural, electrical and thermal characteristics was investigated. XRD patterns revealed the presence of cristobalite (SiO 2) in sintered borosilicate glass and that the addition of Al 2 O 3 hinders cristobalite formation. This behavior is due to the diffusion of some Al 3+ ions from alumina to glass, which leads to changes in glass structure and composition as identified by SEM/EDS. Cristobalite was undetected in composites containing 10% Al 2 O 3 that attained the lowest thermal expansion coefficient value ($4.6 Â 10 À6 °C À1). Conductivity (dc and ac) increased with the amount of Al 3+ ions present in the glass structure as modifiers and formers. Dielectric constant values, in the range 5.0–7.2, increased with Al 2 O 3 addition and the values of loss tan d (1.5–2.1 Â 10 À2) indicate that these materials are good insulators.
Journal of Materials Science: Materials in Electronics, 2009
Five samples of glass/ceramic composites were prepared from borosilicate glasses and both nano-aluminum oxide and nano-titanium oxide. The glass composite samples contain 10, 20, 30, 40, 50 wt.% of alumina and titania mixture. The ratio of Al 2 O 3 :TiO 2 in the mixture was 1:1. The formation of cristobalite in the glass matrix of low firing glass/ceramic composite substrates limits the efficiency of the ceramic substrate when it is used in circuit boards. In the present study, addition of both alumina and titania to a borosilicate glass as a ceramic filler caused the diffusion of alumina and titania phases (anatase and rutile) constituents into the glass matrix and prevented the formation of a cristobalite. Addition of both the ceramics suppresses cristobalite formation more effectively than one of them used alone and results in lower dielectric constant and thermal expansion coefficients.
Dielectric behavior of lanthanum added barium strontium titanate borosilicate glass ceramics
Barium strontium titanate borosilicate glasses were prepared by melt-quench method and subsequent crystallization by regulated heat treatment process. The dielectric behavior of investigated glass ceramic samples shows a diffuse phase transition. The double relaxation was observed in one of the glass ceramic samples due to crystallographic transition from orthorhombic to tetragonal and tetragonal to cubic structure with change in temperature. The peak values of dielectric constant and dielectric loss of this glass ceramic sample was found to be 48,289 and 0.01, respectively, at frequency 20 Hz. Lanthanum oxide served the purpose of nucleating agent for crystallization of glass ceramics and hence, enhances the value of dielectric constant. Such glass ceramics may be used in making capacitors for high energy storage purpose.
Ultra-Low Temperature Sintering and Dielectric Properties of SiO2 -Filled Glass Composites
Journal of the American Ceramic Society, 2013
Ultra low temperature co-fired ceramics system based on zinc borate 3ZnO-2B 2 O 3 (3Z2B) glass matrix and SiO 2 filler was investigated with regard to the phase composition, the microstructure and the dielectric properties as functions of the filler content and sintering temperature. The softening temperature of 554°C and the crystallization temperature of around 650°C for the glass were confirmed by Differential Thermal Analysis result. The X-ray diffraction results show that all SiO 2-filled samples were made up of SiO 2 , a-Zn(BO 2) 2 , Zn 3 B 2 O 6 phases. And there was no chemical reaction between SiO 2 and the glass during densification. And then the dielectric constant decreased with the increasing content of SiO 2. At the level of 15 wt% SiO 2 addition, the composites can be densified at a sintering temperature of 650°C for 30 min, and showed the optimal dielectric properties at 1 MHz with the dielectric constant of 6.1 and the dielectric loss of 1.3 3 10 À3 , which demonstrates a good potential for use in LTCC technology. N. Alford-contributing editor Manuscript No. 32881.
Bulk transparent barium strontium titanate borosilicate glasses in glass system (65-x)[(Ba 0.6 Sr 0.4).TiO 3 ]-30[2SiO 2 .B 2 O 3 ]-5[K 2 O]-x[A 2 O 3 ], A ¼ La, Fe (x ¼ 2, 5 and 10) were prepared by rapid melt-quench technique and subsequently, converted into glass ceramics by regulated heat treatment process. The phase identification was carried out by X-ray powder diffraction and their surface morphology was studied by scanning electron microscopy. The dielectric properties were studied by impedance spec-troscopic technique. Investigated glass samples were crystallized into major and secondary phases of Ba 1.91 Sr 0.09 TiO 4 and Ba 2 TiSi 2 O 8 , respectively. A very high dielectric constant having value upto 68000 was found in glass ceramic sample BST5K10F. This high value of dielectric constant was attributed to inter-facial polarization, which arose due to conductivity difference among semiconducting crystalline phases, conducting grains and insulating grain boundaries. Donor dopant La 2 O 3 and acceptor dopant Fe 2 O 3 play an important role for enhancing crystallization, dielectric constant and retardation of dielectric loss in the samples. Moreover, higher value of dielectric constant and lower value of dielectric loss was found in Fe 2 O 3 doped samples in comparison to La 2 O 3 doped samples.
Materials Research Express, 2020
Different compositions (x) of lead-bismuth titanate borosilicate (PBTB) glasses have been synthesized using a conventional melt-quenching method in the compound 55[(Pb x Bi 1−x)TiO 3 ]−44[2SiO 2 .B 2 O 3 ], (x=0.0, 0.3, 0.5, 0.7 and 1.0) mixed with 1 mol % of graphene nanoplatelets (GNPs). XRD analysis exhibited the synthesis of clear PBTB glasses which confirmed the amorphous nature. Synthesized glasses have been converted into glass-ceramics (GCs) using a differential thermal analysis (DTA) results to understand the crystallization mechanism. XRD results described the crystalline behavior of GC samples and distinct phase formation. The surface morphology of the GCs was analyzed using a scanning electron microscope (SEM). Energy dispersive X-ray analysis (EDAX) have been also performed to verify the elemental composition of the GC sample, PBTG0.5735 F (x=0.5). The variation in relative dielectric constant (ε r) and dissipation factor (D) by increasing temperatures was obtained at different frequencies. The GC sample PTG1.0746 F (x=1.0) showed a maximum value of dielectric constant among all glass ceramic samples.
Egyptian Journal of Chemistry, 2021
Borosilicate glass recycling is a challenge because it has high melting point and different chemical structure which makes it non-recyclable in the glass industry. This work focuses on borosilicate recycling through the preparation of a low thermal expansion and chemically durable borosilicate glass-ceramic composite (BsGC). Low thermal expansion and high chemical durability ceramics are advantageous in many applications such as lab supplies, corning ware, automobile components, and other low expansion products that are resistant to thermal shock. Kaolin and borosilicate were chosen for the preparation of glass-ceramic composite, because they have low thermal expansion and good chemical durability. BsGC was prepared by sintering borosilicate glass waste (e.g., Pyrex laboratory glassware, household glass) and kaolin at different temperatures (750-900 ° C). Water absorption method was used to measure the apparent porosity of the prepared composites. Surface morphology of the prepared BCGs was investigated using scanning electron microscopy (SEM). Phase composition of the prepared BGC samples was characterized using X-ray diffraction technique (XRD). The XRD results showed that at sintering of 750 °C a monocrystalline quartz was only existing. By increasing sintering temperature up to 800°C the quartz phase decreased, while at 850 o C the quartz phase completely disappeared. The sintered BCG composites obtained exhibited low coefficients of thermal expansion in the range of 48 x 10-7 o C-1 and exhibited high chemical durability.
Transactions of the Indian Ceramic Society, 2010
In a lead-free low temperature sinterable multicomponent barium zinc borate glass system, BaO-ZnO-B 2 O 3-SiO 2-Li 2 O-Na 2 O (BZBSLN), the influence of SiO 2 (amorphous) and Al 2 O 3 (crystalline, alpha alumina) ceramic fillers on the softening point (T s), glass transition temperature (T g), coefficient of thermal expansion (CTE), and dielectric constant ( r) has been investigated with a view to its use as the barrier ribs of plasma display panels (PDPs). The interaction of fillers with glass which occurred during sintering at 570 o C has also been studied by XRD and FTIR spectroscopic analyses. It is observed that the filler has partially dissolved in the glass at the sintering temperature leaving some residual filler which results in ceramic-glass microcomposites. The distribution of fillers in the glass matrix and microstructures of the composites have been analyzed by SEM images. It is seen that the T s , T g , CTE and є r are slightly increased as the increase of Al 2 O 3 content. While in the case of SiO 2 filler, the T s and T g gradually increase whereas CTE and є r gradually decrease along the addition of SiO 2 increases. These experimentally measured properties have also been compared with those theoretically predicted