Calcium Borosilicate Research Articles

A Novel Approach to BaTiO3-based X8R Ceramics by Calcium Borosilicate Glass Ceramic Doping

High-performance X8R dielectric materials could be sintered at 1150°C by doping calcium borosilicate (CBS) glass ceramic into the BaTiO3-Nb2O5-ZnO system, with a dielectric constant greater than 1800 and a dielectric loss lower than 1.0%. The effects of CBS, Nb2O5, and ZnO on the dielectric properties were discussed in this article. The X8R specification was achieved with the content of CBS ≥ 4 wt.%, Nb2O5 ≥ 1.0 mol%, and ZnO ≤ 2.0 mol%. The sample doped with 4 wt.% CBS exhibited the highest density and lowest dielectric loss in our experiment. A reduction in grain size was observed in the specimens with 4 and 7 wt.% CBS as compared with CBS-free specimen, whereas the abnormal growth of rectangle-shaped grains took place in the 10 wt.% CBS-doped specimen. The Curie point progressively moved to higher temperatures with CBS content up to 7 wt.%. However, Tc of the sample decreased slightly in the case when 10 wt.% CBS was doped. X-ray diffraction (XRD) analysis indicated that the crystal structure of sintered ceramics changed from tetragonal to pseudocubic symmetry as increasing CBS content.

Characteristics of thick film resistors embedded in low temperature co-fired ceramic (LTCC) substrates

Commercial thick film resistors were embedded in low temperature co-fired ceramic (LTCC) substrates, and co-fired with substrates at temperatures between 800 and 900 °C. Adding glass frit and amorphous SiO 2 to calcium borosilicate glass ceramic substrates has not only lowered the shrinkage of the substrates, but also improved adhesion and maintained structure integrity of the resistor films. During sintering, the conductive phase particles in the resistor became agglomerated and sedimented, and glass diffused into the LTCC substrate layer. Increasing the dwelling time, the overall resistivity of the co-fired films decreased due to sedimentation of agglomerated conductive particles. The liquid eutectic phases penetrated into the substrates added with either SiO 2 or glass frit that the volume fraction of conductive particles was increased. The resistivity of the embedded resistors was determined by the volume fraction of conductive particles, which was influenced by the conductive particles sedimentation, microstructure of resistor films, and inter-diffusion between the resistors and substrates.

Doping effects of Mn2+ on the dielectric properties of glass-doped BaTiO3-based X8R materials

In this paper, Mn2+ and calcium borosilicate glass (CBS) were used as effective dopants to prepare environmentally friendly dielectric materials satisfying EIA X8R specification. The effects of various Mn2+ concentrations on the dielectric properties of BaTiO3 (BT) ceramics were investigated when CBS amount was fixed. The dielectric measurements showed that the permittivity was decreased continuously with increasing Mn2+ concentrations, resulted from the existence of paraelectric regions caused by Mn2+ doping. The dielectric loss was decreased at the beginning and then increased with increasing Mn2+ concentrations, whereas the resistivity showed an opposite movement. The SEM images and X-ray diffraction curves corresponding to BT ceramics doped with different Mn2+ amounts proved that Mn2+ can promote the crystallization of CBS glass to form the secondary phase Ca4Mn4Si8O24, which determines the intensity of the high temperature peak (at about 125 °C) of the variation rate curve of capacitance. Moreover, the modification effects of Mn2+ on the dielectric properties of BT have been investigated. It is revealed that a proper usage of Mn2+ can improve the dielectric properties significantly, and Mn2+ and CBS co-doped BT ceramics are promising to develop X8R MLCs.

Phase Separation in a Thick Film Resistor on a Calcium Borosilicate-Based Substrate

A commercially available resistor paste was embedded into a calcium borosilicate glass ceramic substrate. The fabricated packages were sintered in the 700–900 °C temperature range. The interactions between the embedded resistor and the substrate were studied. Two consecutive phase separations were observed. First, at 800 °C, the diffusion of Ca2+ ions from the substrate into the embedded resistors occurred, resulting in the formation of two separated glass phases with high and low SiO2 content. When the reaction temperature increased to 850–900 °C, the separated glass phase composition reached consistent values and the second phase separation stage occurred.

Crystallization Characteristics of Lithium Calcium Gallium Aluminium Borosilicate Glasses

The crystallization processes of lithium calcium gallium borosilicate glass containing Al{sub 2}O{sub 3} have been followed by X-ray diffractometry (XRD), differential thermal analysis (DTA) and scanning electron microscope (SEM). Lithium gallium silicate - LiGaSiO{sub 4} phase was formed as a major constituent during the crystallization of the base glass. Solid solutions of lithium aluminosilicate and lithium aluminium gallium silicate - LiAl{sub 0.5}Ga{sub 0.5}SiO{sub 4} phases were mostly formed as a function of Al{sub 2}O{sub 3}/Ga{sub 2}O{sub 3} ratios in the glasses. Varieties of lithium borate phases including Li{sub 2}B{sub 4}O{sub 7}, {alpha}-Li{sub 4}B{sub 2}O{sub 5}, Li{sub 3}BO{sub 3}, {beta}-LiBO{sub 2} and LiB{sub 3}O{sub 5} phases were detected together with lithium metasilicate and lithium disilicate. Different calcium bearing phases including wollastonite-CaSiO{sub 3}, calcium borosilicate -Ca{sub 2}B{sub 2}SiO{sub 7}, larnite -Ca{sub 2}SiO{sub 4}, rankinite -Ca{sub 3}Si{sub 2}O{sub 7}, and calcium borate -CaB{sub 2}O{sub 4} were mainly detected as a function of heat-treatment in the CaO-containing samples. The role played by the glass oxide constituents in determining the crystallization characteristics and the nature of the crystal phases formed in the glasses are discussed. (orig.)

Dispersion of glass powders in organic media

Adsorption and dispersion behaviors of glass powders in a binary solvent system of toluene and ethanol with poly(vinyl butyral) (PVB) and poly(methyl methacrylate) (PMMA) have been investigated. The composition of glass powder is varied from an optically basic calcium borosilicate glass to an acidic borosilicate glass. The adsorption of PVB is only observed on the basic calcium borosilicate glass while on the acidic borosilicate glass, PMMA is adsorbed. The adsorption characteristics are correlated with the state of particulate dispersion in suspensions using rheological measurements. A relatively poor solvent for polymers increases their adsorption on glass powders, thus improving the dispersion of glass powders in nonaqueous suspensions.

Cosintering of Ni–Zn–Cu Ferrite with Low-Temperature Cofired Ceramic Substrates

Inserting a ferrite layer into a low-temperature cofired ceramic substrate offers the potential of burying inductors in multilayer ceramic substrates. To cofire a ceramic substrate at low temperatures, ferrite must be densified at a low temperature. With the addition of 6 wt%Bi2O3, Ni–Zn–Cu ferrite can be densified at 900°C. The doped Bi2O3 not only lowers the sintering temperature but also increases the permeability of Ni–Zn–Cu ferrite. The “cordierite + borosilicate glass” system is very compatible with Ni–Zn–Cu ferrite after cofiring, but the calcium borosilicate crystallizable glass system is incompatible with Ni–Zn–Cu ferrite. However, with the addition of 10 wt%SiO2 into the calcium borosilicate crystallizable glass system, the incompatibility was resolved.

Effect of the loading rate of the strength of GB-7 ceramics

The effect of the loading rate on the strength of an alumina ceramics of grade GB-7 in air is studied. It is established that the strength of the ceramics decreases substantially with increase in the loading rate due to the interaction between the calcium borosilicate vitreous phase and steam, which causes substantial growth of the microstructural defects existing in the ceramics.

Danburite‐bearing calc‐silicate rocks from the Ascot Hills, Dookie, Victoria

The rare calcium borosilicate danburite occurs with ferro‐axinite, grossular‐andradite, vesuvianite, tourmaline, chlorite, fluorite, quartz and calcite in a small exposure in the Ascot Hills, 8 km south‐southwest of Dookie, in north central Victoria. The assemblage forms discontinuous bands and lenticular patches within metamorphosed fine‐grained Cambrian greenstones of the northern Mt Wellington Belt, adjacent to the Dookie Fault. The minerals represent boron metasomatism superimposed on burial metamorphism to greenschist facies. The Dookie Fault acted as a channelway for the boron‐rich solutions. The boron was probably remobilised from within the greenstone sequence, either from lavas which exchanged boron with seawater during emplacement, or from siliceous marine sediments, now cherts, interbedded with the volcanic rocks. Solution composition was probably the major influence in determining whether danburite or datolite crystallised. This occurrence is only the second record of danburite in Australia.

Fusible glazes based on calcium borosilicate glasses

Fusible glazes based on calcium borosilicate glasses

Activities and structure of some borosilicate melts

The application of structural models to some calcium borosilicate melts was made to develop simple expressions of activities as functions of composition. Their applicability was tested with freezing point depression data from phase diagrams. The activity values obtained were compared with those computed from the calorimetric heat of fusion. Data from published phase diagrams for the systems Ca 2 B 2 O 5− Ca( BO 2) 2, Ca 3( BO 3) 2− Ca 2 SiO 4, Ca( BO 2) 2− CaSiO 3, and Ca 2 B 2 O 5− CaSiO 3 were used. Simple ionic models seemed applicable to melts where isolated ions may be expected; in melts containing mixed ions in chains and rings, the so-called “group” model may be useful. The authors, are respectively, Professor of Engineering, University of California, Los Angeles, and Professor of Inorganic Chemistry and Director, Institute of Silicate Science, Norwegian Institute of Technology, Trondheim, Norway.