• Journal of the Korean Crystal Growth and Crystal Technology
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• v.30 no.4
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• pp.136-142
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• 2020

Crystallization of zinc crystalline glaze requires demanding conditions such as the formation of a nucleating agent and the amount of nucleating agent, and growth of crystalline. Zinc crystalline glaze is hard to utilize in the industry because of its narrow range of the firing temperature, and the crystallization's dependency on the quality of zinc. Stimulation of zinc crystallization and formation of frit enable zinc crystalline glaze to be reconstituted in a various range of firing schedules, leading to the development of a competitive industrial glaze.

• Journal of the Korean Ceramic Society
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• v.50 no.2
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• pp.116-121
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• 2013

Zinc crystal glaze has its limits in practical use of commercial glaze due to the controlling crystal. In order to overcome this limit, and to heighten the practical usage, this study is aimed to develop artificially controlling willemite ($Zn_2SiO_4$) zinc crystalline glaze. For this purpose, it has experimented with the effect of anatase form and rutile form using $TiO_2$ known as nucleating agent. In zinc glaze, adding $TiO_2$ resulted with anatase form becoming more effective at nucleating formation and growth of willemite than the rutile form. Furthermore, it turned out that using the $TiO_2$ - anatase form, with synthetic seeds (zinc silicate), the numbers and positions of crystals can be controlled artificially.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.24 no.2
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• pp.70-76
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• 2014

$Zn_2TiO_4$, using an anatase form of $TiO_2$ on zinc crystalline glaze, was shown as effective nuclear agent. Thus the effects on glaze were studied with synthesized $Zn_2TiO_4$ at low temperature. First, the chromophore elements were employed in synthesized $Zn_2TiO_4$ then add them in the zinc crystalline glaze. Crystal creation and development of color by $Zn_2TiO_4$ addition on the zinc crystalline glaze were more effective. Addition of $Zn_2TiO_4$, which is developed in low range temperature, is effected as zinc crystalline nuclear in the willemite glaze. When 5 wt% of synthesized $Zn_2TiO_4$ was added to the willemite glaze, nuclear creation increases and steadily retains. Therefore addition of respectively doped $Zn_2TiO_4$ with CoO, NiO, and CuO would increase doped effects in the glaze, various color willemite crystal were obtained.

• Journal of the Korean Ceramic Society
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• v.48 no.2
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• pp.121-126
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• 2011

The study investigates the effects of a body that influences the nucleation and growth of crystal by experiment the application of zinc crystalline glaze to five of the most favorably used kinds of bodies sold in the market. As a result, in all bodies used in the test, willemite crystal is appeared on the surface and in the case of white porcelain, super white and white porcelain sculpture clay, beautiful crystals is developed. The reason that crystal does not grow and trickle down by sticking to the body in celadon clay and Sanchung clay is the large surface tension of glaze by ingredient CaO which is more often present compared to other bodies. In glaze, the ingredients $Al_2O_3$ and RO greatly influences the surface tension, and adhesion of the glaze and the body is completed by the glaze's power to stick, which is determined by the reaction of both the glaze and the body. However, in the case of Sanchung clay, the CaO in body reacts to the glaze, and glaze, on Sanchung clay, has tendency to run more compared with other bodies. It is supposed that this mechanism influences the growth of willemite crystal and the glaze's adhesion to the body.

• Journal of the Korean Ceramic Society
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• v.46 no.3
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• pp.253-262
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• 2009

The purpose of this study is to find out optimum conditions for zinc crystalline glaze under variables of firing: maximum firing temperature, crystal growth temperature, temperature increasing speed, annealing speed, holding time at maximum temperature and holding time at crystal growth temperature. Ferro Frit3110, ZnO and Quartz were used as starting materials and tested by three component system. The best result of test was selected and extended to its vicinity as five glaze formulas. And then the specimens were experimented by variable firing conditions and analyzed by crystal appearance observation, XRD, FT-IR and Raman spectroscopy. In result, main crystal was willemite in the zinc glazes. Some gahnite was detected in specimens which were fired at $1230^{\circ}C$, $1250^{\circ}C$ and $1270^{\circ}C$, however gahnite was not identified at $1300^{\circ}C$. Optimum zinc crystalline glaze was gained by following firing condition: temperature increasing speed $5^{\circ}C$/min, holding 1 h at $1270^{\circ}C$, annealing speed $3^{\circ}C$/min till $1170^{\circ}C$, holding 2 h at $1170^{\circ}C$ then naturally annealed.

• Journal of the Korean Ceramic Society
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• v.47 no.6
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• pp.598-602
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• 2010

When metal oxides are added into crystalline glaze, colors of glaze and crystals are similar as colorants generally. But the case of NiO in zinc crystalline glaze is different from general color development. When NiO is added to zinc crystalline glaze it can develop two or three colors. The active use of color development mechanism by adding NiO to the zinc crystalline glaze to control color of the base glaze and crystal with stability is investigated. This report is expected to contribute to the ceramic industry in improving application of zinc crystalline glaze. For the experiment of NiO, the quantity of NiO additives is changed to the base glaze for the most adequate formation of willemite crystal from previous research and firing condition: temperature increasing speed $5^{\circ}C/min$, holding 1 h at $1270^{\circ}C$, annealing speed $3^{\circ}C/min$ till $1170^{\circ}C$, holding 2 h at $1170^{\circ}C$ then naturally annealed. The samples are characterized by X-ray diffraction (XRD), UV-vis, and Micro-Raman. The result of the procedure as follows; Ni substitutes for Zn ion then glaze develops blue willemite crystals, as if cobalt is used, on brown glaze base. When NiO quantity is increased to over 5 wt%, willemite size is decreased, and the density of the crystal is increased, at the same time $Ni_2SiO_4$ (olivine) phase, the second phase, has been developed. The excessive NiO is reacted with silicate in the glass then developed green $Ni_2SiO_4$ (olivine), and quantity of $Ni_2SiO_4$ (olivine) is increased as quantity of willemite is decreased. It is proved to create three colors, blue, brown and green by controlling the quantity of NiO to the zinc crystalline glaze and it will improve the multiple use of colors to the ceramic design.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.33 no.6
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• pp.234-243
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• 2023

Zinc crystals of ZnO and SiO₂ in glaze raw materials, developed according to composition and firing requirements, are preferred because of their high decorative properties. However, most zinc crystal glazes have a high firing temperature and a narrow firing temperature range, making it difficult to use them as commercial glazes in ceramics. Therefore, in this study, it was expected that the firing temperature of a typical zinc crystal glaze could be lowered to below 1270℃ by using the eutectic effect through mixing frit, the main raw material used in manufacturing zinc crystal glaze. As a result, not only was the formation temperature of zinc crystals lower in the mixed frit glaze, but also the firing temperature range was widened to 1230~1270℃, making it possible to develop a glaze that produces crystals stably. The firing temperature was lowered to 1230~1250℃ and the holding temperature during cooling was lowered to about 950℃, resulting in the development of an economically effective glaze. When using a combination of frit, it has been shown that the holding temperature during cooling affects the recrystallization of zinc crystals depending on the composition of the glaze, and the crystal structure can be adjusted at this time. Additionally, the amount and shape of crystals can be controlled by using a nucleating agent.

• Journal of the Korean Ceramic Society
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• v.52 no.3
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• pp.197-203
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• 2015

The colorization of $Zn_2SiO_4$ crystal glazes was investigated by adding nucleating seeds with various coloring agents. The addition of color fixing agents such as $Fe_2O_3$, $MnO_2$, and NiO with seeds caused changes in the colors of glazes. The crystallinity and crystal size were dependent on glaze composition and firing schedules. By controlling coloring agents and firing schedules, it was possible to create various colors and sizes of crystals in a zinc-based crystalline glaze.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.6
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• pp.240-246
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• 2021

In the ceramic industry, a drastic decrease in crystalline formation was found even among the glazes well known for their high crystalline productivity when the ceramic glaze was stored in wet conditions over a period. This study aimed to investigate the reason for decreasing willemite crystals during storage. As the starting materials ZnO, calcined ZnO and frit 3110 are selected; the composition for zinc crystalline glazes was set through a three-component system with the materials. The firing condition was used from previous studies. The study was observed how wet conditions affected the crystallization of zinc crystalline glazes from a day to 24 weeks. The results were obtained by particle size analysis, XRD, Raman spectroscopy and SEM analysis. The results indicated that ZnO is advantageous in terms of willemite crystalline development and growth; however, Zn(OH)₂ cluster, formed by the reaction with water during the storage, caused the decrease in ZnO level in the glaze. The reduction of ZnO in the glaze eventually interfered the willemite development and growth.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.27 no.1
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• pp.34-41
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• 2017

In this study, the effect on the zinc nuclei crystallization caused by changes preprocessing of the zinc crystalline glaze preparation has been studied. The mechanism of the nuclei formation in the crystalline glaze and development of the nuclei by studying the preprocessing step was explained. The preprocessing step was improved by altering mixing process of the materials prior to sintering: number of sieving dispersion process and ultra-sonication prove tests with various duration of sonication. According to the result, the sieving and sonication of the starting materials facilitated the interface reactions of $ZnO-SiO_2$ from $680^{\circ}C$ where low temperature willemite is formulated, and altered Si bonding for the easier bonding between Zn-Si. In other words, solely sieving was enough to accelerate the formation of willemite in low temperature. When the particles were distributed evenly by sonication, the willemite formation was even more significant.