• Journal of the Korean Ceramic Society
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• v.35 no.12
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• pp.1274-1279
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• 1998

The glass forming ability of the PbO-B2O3-TiO3-BaO system was investigated in relation to transitieon tem-peratures and the atomic ratio between constituents. Glass forming tendency was improved as the tem-peratures and the atomic ratio between constituents. Glass forming tendency was improved as the tem-perature differences between liquidus temperature and crystallization(or glass transition) temperature de-creased and the temperature difference between crystallization and glass transition temperature increases. The atomic ratio could be used as a criterion to deign glass systems. The interposition of B and Ba atoms between Pb and Ti atoms was one of important factors in glass formation.

• Journal of the Korean Ceramic Society
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• v.32 no.12
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• pp.1331-1336
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• 1995

The glass-ceramics for ferro-electric were made from compositions of 70PbO.16TiO2.8SiO2.4B2O3.2AlPO4 (wt%) and 67.5PbO.20TiO2.8.5SiO2.2B2O3.2AlPO4 (wt%). The crystallization kinetics for PbTiO3 crystalline phase formation from glass was studied using non-isothermal DSC techniques. The values of activation energy, ΔE using variables of heating rate and temperature were calculated at various reaction fractions obtained from peak area over DSC. The results indicated that activation energy was lowest at 60% reaction fractions and the activation energy of glass containing 20.0 wt% TiO2 is higher than that of glass containing 16.0 wt% TiO2. The crystallization mechanism was three dimensional growth (n=4).

• Journal of the Korean Ceramic Society
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• v.29 no.10
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• pp.765-772
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• 1992

As the fundamental research of preparation of fine single crystalline ferroxplana by means of glass-crystallization methods using steel twin-roller the properties of ferroxplana extracted from cyrstallized glass were studied. Most of all the specimens quenched by twin-roller at about 1350$^{\circ}C$ were glass phase, the crystallization of these glass had multi-steps and ferroxplana phase was only stable untill 900$^{\circ}C$, began to be decomposed from about 950$^{\circ}C$ in glass. The morphology of particle could be controlled by the composition and crystallization condition, and Zn2+ was replaced by reduced Fe2+ which is 2∼3% contents of total Fe. Ferroxplana extracted had such magnetic properties as Ms=34 emu/g, mHc=10 Oe and Curie Temperature, Tc=425K.

• Journal of the Korean Ceramic Society
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• v.29 no.10
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• pp.779-784
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• 1992

In producing cordierite glass-ceramics by sintering, following experiments were conducted in order to determine the optimum heat-treatment schedule for high-crystallinity and dense sintered body. The glass composition of 11.67MgO-29.46Al2O3-52.88SiO2-5P2O5-1B2O3 (wt%) was selected on the basis of the early experiment. The 3-step heat treatment schedule was determined by the results of DTA, Dilatometric measurement and high-temperature XRD, where the particle-size-controlled glass powder was used. The degree of densification and the crystallinity were evaluated by the measurement of the bulk density and X-ray scattering intensity. The specimen fired with the optimum conditions showed ${\alpha}$-cordierite phase, relative density ∼98%, crystallinity ∼92%, thermal expansion coefficient ∼30${\times}$10-7/$^{\circ}C$, dielectric constant ∼5.5 and resistivity ∼1.0${\times}$1012 {{{{ OMEGA }}cm, respectively.

• Journal of the Korean Ceramic Society
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• v.29 no.10
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• pp.815-821
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• 1992

The batches having excess SiO2 to tetrasilicic mica KMg2.5 (Si4O10)F2 were melted at 1450℃. The fabricated samples were heat-treated for the nucleation and the crystallization. The crystallized samples were investigated on several properties. The tetrasilicic mica composition with excess 10 wt% SiO2 was successful both in glassifying and in crystallizing. The optimum temperatures for the nucleation and the crystallization were 680℃ and 1000-1100℃, respectively. The mica and the cristobalite crystallines were identified after heat-treatment. The properties of the samples processed appropriately were as follows, bulk density 2.64g/㎤, thermal expansion coefficient ∼80×10-7/℃, Vicker's hardness ∼105 Kgf/㎟, bending strength ∼666Kgf/㎟, dielectric constant ∼11.1, tan δ 2.5%, volume resistivity 2.35×107∼1.3×1011{{{{ OMEGA }}cm, surface roughness 6.984㎛.

• Journal of the Korean Ceramic Society
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• v.30 no.12
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• pp.1054-1058
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• 1993

The effects of TiO2 addition as a nucleating agent on the cordierite glass-ceramics were investigated. The glass compositiion was stoichiometric cordierite composition of 13.7MgO-34.9Al2O3-51.4SiO2(wt%), and TiO2 as a nucleating agent was added by 5, 10 and 15wt% in addition. The optimum amount of TiO2 addition and appropriate heat treatment schedule were determined by using dilatometer, DTA, XRDA and SEM. The composition containing 10wt% TiO2 was proved to be the best among the investigated compositions. And the optimum heat treatment schedule was 840℃-2h for the nucleation and 1140℃-2h for the crystallization. The properties were as follows. The crystallinity was ∼75%, thermal expansion coefficient 33×10-7/℃(25∼700℃), dielectric constant 7.6(1KHz) and Vicker's hardness 5.1GPa.

• Journal of the Korean Ceramic Society
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• v.28 no.5
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• pp.406-414
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• 1991

The composition of base glass was selected as MgO 8, Al2O3 24, SiO2 68 in weight percent. TiO2 and ZrO2 were added to the base glass to investigate their effects as nucleating agents. In the case of ZrO2 addition, the optimum temperature for nucleation, which was related to the precipitation of tetragonal ZrO2, was 80$0^{\circ}C$. The optimum growth condition for the crystal was 87$0^{\circ}C$ for 8 hrs, and the major crystal phases precipitated in the samples were $\beta$-quartz ss. and mullite. The light transmissivity turned out to be around 80 per cent. On the other hand, when the TiO2 was added, it was difficult to determine the nucleating temperature, because the samples turned easily into translucency during the heat treatment. Therefore, it was almost impossible to retain transparency in the samples. The light transmissivity was below 30 per cent.

• Journal of the Korean Ceramic Society
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• v.33 no.7
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• pp.809-815
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• 1996

When Li2O.2SiO2 glass was crystallized between the temperature of maximum nucleation and the temperature of maximum crystal growth it was found that the control of heating rate had serious effect on the crystallinity and microstructure and the greatly changed physical properties. Density and elastic modulus tends to increase but thermal expansion coefficient decreased with increased crystallinity. When heating rate between the tempe-rature of maximum nucleation and the temperature of maximum crystal growth was 10~5$0^{\circ}C$/hr. crystallinity was increased to result in the increment of strength. When nuclation was done at 44$0^{\circ}C$ for 5 hours and the temperature of crystal growth was held at 575$^{\circ}C$ strength was increased until crystallinity reached 65% and strength was decreased with higher crystallinity. These phenomena could be explained that even for the same crystallinity different heat rates resulted in different number and size of cracks.

• Journal of the Korean Ceramic Society
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• v.37 no.1
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• pp.82-89
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• 2000

In lithium silicate photosensitive glass-ceramics, the relationship between lithography time and crystallization, and the effect of addition of mineral acid in etching rate and pattern shape were investigated. Irradiation times for micropatterning were less than 5 minutes in which Ce3+ ions in glass were changed rapidly to Ce4+ with ultra violet light. Overexposure to ultra brought about blot of pattern by diffiraction of light. Addition of mineral acid to HF enhanced etching rate as compared with HF solution only. The addition of H2SO4 especially increased the etching rate by 70%. But the mixed solution also increased the etching rate of the noncrystallized portion of the glass and this resulted in heavy etching. Etching with ultrasonic wave showed higher etching rate than that with the static or fluid method.

• Journal of the Korean Ceramic Society
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• v.11 no.3
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• pp.19-26
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• 1974

Mechanical properties of the system PbO-B2O3-V2O5 low melting glass during crystallization by heat-treatment were investigated. Wettability of the system PbO-B2O3-V2O5 was excellent and appropriate for commercial sealing as a low melting solder glass. Crystals, during heat-treated at 30$0^{\circ}C$ of the system PbO-B2O3-V2O5 were $\beta$-4PbO.B2O3, 5PbO.4B2O3, and Pb2V2O7 mainly. The percent of crystallinity was 82$\pm$5%. Mechanical properties of the system PbO-B2O3-V2O5 were influenced not only by the differences of density and coefficient of thermal expansion and the stress induced from the difference in the density and coefficient of thermal expansion between glass phase and crystals but also crystallization conditions.