Preparation of separative-phase fancy glaze derived from iron ore slag

The separative-phase fancy glaze was successfully prepared by using the iron ore residue as the ceramic colorant. A possible coloring mechanism was proposed to explain the variation of glaze colors and patterns with the increasing of firing temperature. Effects of the firing temperature on the chromaticity, precipitated phase and microstructure of separative-phase fancy glaze were investigated. The results indicated that with increasing the firing temperature, the content of whitlockite decreased while the size of phase separation droplets in glazes increased. The residual whitlockite weakened coloring of Fe₂O₃ and formed glaze patterns. In addition, the increased size of phase separation droplets weakened the structural color, which increased the L* and b* value of glazes. Therefore, the color of separative-phase fancy glaze got more yellow and brown gradually.     

The morphology and structure of crystals in Qing Dynasty purple‐gold glaze excavated from the Forbidden City

Ancient Chinese purple‐gold glaze (zijinyou) is popular for its beautiful figuration, unique allure and fine craftsmanship. To understand the crystalline nature in the purple‐gold glaze, the morphology and structure of crystals precipitated in the glaze layer of purple‐gold glaze porcelain fired during the Qing Dynasty were characterized by a variety of methods combining X‐ray and electron‐based techniques. A large quantity of single‐phase twinning ε‐Fe₂O₃ crystals with lengths of 1‐3 μm, widths of less than 1 μm, and thickness of approximately 150 nm are found dispersed across the glaze surface to a depth of approximately tens of micrometers. These crystals show stratification across the cross‐section of the purple glaze consisting of 4 sublayers according to the crystal size. The formation of ε‐Fe₂O₃ crystals primarily contributed to the reddish‐brown tones of the purple‐gold glaze. The presence of anorthite, a strong reducing atmosphere during the firing process and the vitreous nature of the glaze influenced the growth of ε‐Fe₂O₃ crystals. These results suggest the controllability of single‐phase ε‐Fe₂O₃ crystals by identifying and understanding the underlying chemical processes in ancient Chinese crystalline glaze porcelain, and the findings will provide insights for modern material scientists in preparing ε‐Fe₂O₃ crystals with large sizes and high purities.     

Firing process and colouring mechanism of black glaze and brown glaze porcelains from the Yuan and Ming dynasties from the Qingliang Temple kiln in Baofeng,Henan, China

Black glaze and brown glaze porcelains were an important part of ancient Chinese iron-based high temperature glazes. The excavation of black glaze and brown glaze porcelains from the Yuan and Ming dynasties at the Qingliang Temple kiln site in Baofeng, Henan, China, in 2014, enriched the firing history of this kiln site and history of Chinese ceramics. In this study, black glaze and brown glaze porcelain samples from the Qingliang Temple kiln site from the Yuan and Ming dynasties were selected and analysed via optical microscopy, laser Raman spectroscopy, focused ion beam scanning electron microscopy combined with EDS and energy dispersive X-ray fluorescence to determine their microscopic morphology, microzone composition, microstructure and chemical composition. Moreover, the main wavelength range of the brown glaze porcelain samples were measured by UV–Vis–NIR spectrophotometer systems. The main conclusions of this study are as follows. The brown glaze porcelain from the Yuan and Ming dynasties at the Qingliang Temple kiln site has two different colour layers, with the surface is brown and the bottom is black. The presence of a glass phase and α-Fe₂O₃ phase in the black glaze porcelain samples, and a rare ε-Fe₂O₃ phase in the brown glaze porcelain samples. The brown colour was a result of ε-Fe₂O₃ precipitation, whilst the black base layer also enhanced the brown-colouring effect. Different glaze formulations were used for brown glazed porcelain, some of which were similar to those used for black glaze porcelain and derived from the transformation of black glaze porcelain through different firing atmospheres and cooling rates. Although the formula of the brown glaze porcelain samples exhibited differences, the main wavelength difference was not large, was within the 645–682 nm range and belonged to the visible red region.     

Reproduction of phase-separated celadon glazes with Zijin clay

The preparation of R₂O-RO-Al₂O₃-SiO₂-P₂O₅ system phase-separated celadon glaze by using Zijin clay is investigated, which with the potential of environmental protection. Si and SiC were introduced to reduce iron oxide (Fe₂O₃) in an oxidizing environment. UV–vis–NIR, XRD, Raman, XPS, SEM, and TEM were used to explore the effects of reducing agents on the glaze color, microstructure, and phase structures. The results indicated that the introduction of 0.5 wt% Si and 0.5 wt% SiC will change the chemical state of iron ions. More concretely, the ratio of Fe²⁺/Fe³⁺ changed from 22.9/77.1–72.2/27.8 and 60.2/39.8, respectively, and the Si⁴⁺-O-Fe²⁺ was the main coloring factor, which made glazes appear blue green. Among them, the Si⁴⁺ produced by the introduction of Si contributed to the formation of the fancy patterns, but phase separation droplets formed the weak structural color. The glazes with SiC had the Rayleigh scattering effect, which was combined with the chemical color to improve the blue-green lightness of glazes.     

Study on the Five dynasty sky-green glaze from Yaozhou kiln and its coloring mechanism

This work takes the Five dynasty sky-green glaze of Yaozhou kiln as the major study object. Based on the analysis of XRF, XRD, XPS and SEM/EDS, the chemical compositions, firing technique and microstructure of the sky-green glaze were investigated. A possible coloring mechanism was proposed to explain the variation of glaze appearance. The results indicated that the Five dynasty sky-green glaze had relatively high contents of CaO and K₂O, which led to the better gloss and transparency than others. Besides that, the chemical coloring of Fe₂O₃ and the scattering of phyical structures also affected the color saturation and opacity of glaze surface. The high Fe²⁺/Fe³⁺ ratio and phase separation droplets of forming structural color by the amorphous photons and Rayleigh scattering contributed to increasing the blue tone of sky-green glaze. In addition, the residual crystals decreased the transparency of glaze surfaces.     

Raman identification of the different glazing technologies of Blue-and-White Ming porcelains

Shards of Blue-and-White Ming porcelain from shipwrecks of Portuguese ships found on the coasts of South Africa plus a shard from Mombasa (Kenya) were analyzed by optical microscopy, SEM-EDS and Raman microspectroscopy (458 nm). Whereas the Raman signature of porcelain body paste compositions which are based on mullite, quartz and an amorphous phase with the minor presence of anatase and feldspar are very comparable whatever the variable alumina content, at least two types of glazes are observed: a high-temperature soda-potassium glaze, and glazes richer in calcium and similar to a celadon glaze (with the possibility of wollastonite formation). The blue decoration is obtained with a material rich in manganese typical of the Ming productions. Some shards exhibit a two-layer glaze and the blue decoration is either placed under-glaze, or in-glaze as found in the Vietnamese productions of the same period. Previous assignments of the Raman signature of feldspar to cobalt aluminate are now not favoured (blue colour is obtained with Co²⁺ ions dissolved in the glassy silicate) and several black spots exhibit the characteristic spectrum of an epsilon Fe₂O₃ phase being present.     

Phase composition and structure of dull low-melting glazes

The possibility of producing dull low-melting glazes for ceramic products to be fired according to a slow firing regime based on the system Na₂O-MgO-CaO-B₂O₃-Al₂O₃-SiO₂ is demonstrated. The results of studying glaze glasses and coatings by x-ray phase analysis, electron microscopy, infrared microscopy, etc. are described. A correlation between the structure and the phase composition of coatings and their qualitative characteristics is established. The main properties of synthesized dull glazes are specified. __________ Translated from Steklo i Keramika, No. 4, pp. 19–23, April, 2006.     

Morphological and structural study of crystals in black-to-brown glazes of Yaozhou ware (Song dynasty) using imaging and spectroscopic techniques

The Yaozhou kiln complex (Shaanxi, China) is a famous black-to-brown ceramic production center due to its significant volume of production, long manufacturing history (from Tang Dynasty to Yuan Dynasty) and variety of decorations. In this work, four representative types of black-to-brown ware from the Yaozhou kilns were selected to study the morphology, structure and distribution of the precipitated crystals in the glazes using a series of imaging and analytical techniques (optical microscopy, XRF, SEM-EDS, TEM-EDS, μRS and UV–vis-IR). The results show that the rare metastable ε-Fe₂O₃ phase, already observed in typical sauce glaze, was also detected in other types of brown glaze decorations, such as light brown stripes on a darker background or irregular brown spots on a black background. Cross-section analyses also showed a three well-separated layered crystalline distribution in the glazes of lighter brown colors as it has been noted in glazes from Qilizhen kilns. Raman analyses revealed that the crystals contained in third layer are of varying nature: ε-Fe₂O₃ in the sauce glaze and magnetite in the light brown stripes. The peak shifts and line broadenings observed in the Raman spectra of ε-Fe₂O₃ crystals were also investigated. They are the result of Al, Ti and Mg substitutions, which were identified using TEM-EDS. Such ionic substitutions would stabilize the metastable ε-Fe₂O₃ crystals by increasing the cationic disorder. In addition, Mg-, Ca- and Fe-rich spinel crystals were observed for the first time in a black glaze of Yaozhou wares.     

Effect of phase separation on the Jian ware blue colored glaze with iron oxide

This study was aimed to explore the effect of phase separation on the Jian ware blue colored glaze with iron oxide. In order to analyze the forming cause of glaze patterns and their coloring mechanism, the phase, microstructure and chemical state of the samples were investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectrum. The results indicated that the addition of calcium phosphate introduced highly-active Ca²⁺ and P⁵⁺ into the glaze. Since Ca²⁺ with high ionic potential had a greater ability to appeal O^2? than Si⁴⁺, the glaze melt was separated into calcium-rich phase and silicon-rich phase. The difference of viscosity caused the non-uniform distribution of quartz and glass phase, and then affected the distribution of iron ions in two phases, which formed glaze patterns. Adding P⁵⁺ that had a strong effect of reversed polarization on the Fe-O increased the contents of Fe²⁺ and Fe³⁺-O-Fe²⁺, and thus deepened the blue-green of glaze surface. In addition, it promoted the formation of worm-like phase-separated structures and the existence of structural color. Therefore, phase separation enriched not only patterns but also glaze colors of the Jian ware blue colored glaze.     

The thermal and microstructural behavior of a R2O–RO–(ZnO)–Al2O3–(TiO2)–SiO2 based macro-crystalline raw glaze system

Macro-crystalline glazes containing significantly large crystals visible to the naked eye are a type of artistic glaze with a decorative and esthetic performance. The use of raw glaze compositions is a cost effective alternative for these types of crystal glazes. In the present study, R₂O–RO–(ZnO)–Al₂O₃–(TiO₂)–SiO₂-based raw glaze system was studied to produce macro-crystalline glazes for Limoges porcelain bodies. The influence of the addition of TiO₂ as a nucleating agent or major phase was evaluated in zinc-based glazes as well as ZnO-free ones. Designed glaze compositions were fired according to a special heat treatment cycle and characterized in terms of thermal and microstructural behavior using a digital microscope, differential thermal analyses, hot stage microscopy, X-ray diffraction, a scanning electron microscope, and energy-dispersive X-ray spectroscopy.     

Iron and chromium doped perovskite (CaMO3 M = Ti,Zr) ceramic pigments,effect of mineralizer

Solid solutions Ca(D_xM_1?x)O₃ (M = Ti, Zr and D = Fe,Cr), have been studied as ceramic pigment in conventional ceramic glazes using 0.5 mol/mol of NH₄Cl as flux agent by solid state reaction and by ammonia coprecipitation route. Ca(Cr_xTi_1?x)O₃ compositions obtained without addition of NH₄Cl as mineralizer, produce pink color in glazes at low x but CaCrO₄ crystallizes when x increases, producing undesired green colors. The crystallization of chromates can be avoided using NH₄Cl as mineralizer, giving a complete solid solution that produce pink color in glazes at low x and dark blue shades at high x. Coprecipitated sample produce blue colors at low x and at low temperature than ceramic sample (1000 °C instead 1200 °C for CE sample). Cr⁴⁺ ion acts as red chromophore, but at higher x values (blue samples) Cr³⁺ ion entrance affects the color. Ca(Fe_xTi_1?x)O₃ system crystallizes perovskite CaTiO₃ and pseudobrookite Fe₂TiO₅ together with rutile as residual crystalline phase, glazed samples change from a yellow to a pink color associated to the increase of pseudobrookite with firing temperature. Ca(Fe_xTi_1?x)O₃ and Ca(Cr_xZr_1?x)O₃ systems crystallize perovskite CaZrO₃ and zirconia (ZrO₂) in both monoclinic and cubic polymorphs, but iron or chromium oxides are not detected in the powders. Coprecipitated sample stabilises cubic form. The solid solution is not reached completely in these samples and is not stable in glazes.     

浅论陶瓷铜红釉色的自然美

陶瓷铜红釉是我国著名的色釉之一，以自身的特殊语言来表现其风彩神韵－－自然美，有自己的美学追求。它的自然美依赖于原材料，工艺流程，窑火及陶瓷艺术家的运用与创新。本文从工艺条件的作用，火的艺术，自然美的艺术表现形式三大主要因素及特点出发，通过大量的例证论述陶瓷铜红釉色的自然美。     

Preparation of a highly color-saturated amorphous photonic crystal structural color glaze by imitating the multilayered structure of Jun porcelain

As is well known, a black background can remove the influence of background light reflection and improve the color saturation of amorphous photonic crystal structural color. Coincidentally, a multilayered structure with a black layer of glaze base was found in Jun porcelain. Based on this, black crucible soil with high Fe₂O₃ content was used as the raw material for imitating the multilayered structure. Furthermore, the reason for the formation of the black layer and its influence law on the saturation of structural color glazes were also studied. The results indicated that the diffusion of iron and titanium ions under the concentration gradient promoted the formation of a black layer. In addition, with increasing amounts of black crucible soil, the diffusion amount and depth of the transition metal ions were large, and the black layer was thickened. It was conducive to improving color saturation for the structural color glaze.     

Development of sapphirine opaque glazes for ceramic tiles

The purpose of this work is to produce more excellent opaque wall tile glazes by using sapphirine instead of zirconium silicate as an opacifier. In order to achieve it, the chemical compositions were precisely adjusted in the system of SiO₂-Al₂O₃-MgO-K₂O-Na₂O-B₂O₃. The morphological characteristics of the glaze were determined by differential scanning calorimetry (DSC), X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). And the optical properties of the glaze were characterized by a spectrophotometer and a gloss meter. The results reveal that well-shaped crystals of sapphirine (Mg₂Al₄SiO₁₀) with needle-like morphology were formed as only crystal phase. The glaze is provided with better opacity whiteness and gloss compared with commercial zircon-based glass-ceramic glazes, and it is mainly composed of cheap mineral raw materials. Those features make it as an alternative one for improving the properties of conventional opaque ceramic glazes.     

Migration of harmful substances from colored glazes into model media

The results of investigations of colored glazes containing oxide colorants (Cr₂O₃, CuO, CoO, Mn₂O₃), added to the batch when colored frit is being melted and when the transparent glaze frit is ground, are presented. It is established that these oxides affect the LTEC, the microhardness of the glazes, and the migration of boron, aluminum, chromium, copper, cobalt, and manganese ions out of the coatings into a 4% solution of acetic acid. The relation between the structural changes occurring in colored glassy coatings and the migration of harmful substances out of them is determined. __________ Translated from Steklo i Keramika, No. 6, pp. 19–23, June, 2007.     

The impact of nano-quartz on the structure of glass-ceramic glazes from the SiO2–Al2O3–CaO–MgO–Na2O–K2O system

The present study reports the impact of the introduction of nano-grained quartz (SA = 325 m²/g) into the composition on the structure and properties of the ceramic glaze of the CMAS-Na₂O–K₂O system. The results were compared to the glaze which had an identical oxide composition, with a difference that quartz was introduced in the form of quartz powder with a much smaller specific surface area SA = 1.41 m²/g. Both glazes are characterized by a large part of the glassy phase, above 90% by volume. The results obtained show a higher arrangement of the continuous glassy phase structure in the glaze with the addition of nano-quartz. This glaze also shows significantly higher values for all measured mechanical properties. It seems that if, in the near future, new cheaper methods for the production of nano-quartz are developed, it will be a new interesting direction of research aimed at improving the parameters of glazes and glass-ceramic materials of CMAS type.     

Synthesis of glass-ceramic glazes in the ZnO–Al2O3–SiO2–ZrO2 system

Glazes in the ZnO–Al₂O₃–SiO₂–ZrO₂ system with crystallization ability of gahnite (ZnO·Al₂O₃) and β-quartz solid solution (βqss) were synthesized. The compositions were designed based on calcium and magnesium oxide replacement (from a CaO–MgO–Al₂O₃–SiO₂ glass-ceramic glaze system) with zinc oxide and simultaneous increasing aluminum oxide. By this replacement, diopside eliminated and co-precipitation of gahnite and zirconium silicate observed. However, a little addition of Li₂O changes the crystallization path by precipitation of βq_ss and willemite (2ZnO·SiO₂) at low temperatures (800–900 °C) which dissolved into glaze by development of firing temperature. The experiments showed that while the micro-hardness of gahnite-based glass-ceramic glazes is almost equal with the diopside based one, it is more than the traditional floor tile glazes.     

Study on the coloring mechanism of the Ru celadon glaze in the Northern Song Dynasty

The Ru kiln is one of the five most famous kilns in the Chinese Song Dynasty. To clarify the coloring mechanism of the Ru celadon glaze, the celadon samples from the Ru Guan kiln site of Qingliangsi were analyzed by spectrophotometer, X-ray fluorescence spectrum, Raman spectroscopy, scanning electron microscopy and X-ray photoelectron spectrum. The results indicated that the molar ratios of SiO₂/Al₂O₃ and CaO/(CaO + Al₂O₃) affected the formation of micro-bubbles, anorthite crystals and phase separated structures. A large number of bubbles and anorthite crystals formed special glossiness and opacifying effect in the Ru celadon glaze. And then, dense phase separation droplets in the amorphous region were in short-range order, but their diameters (31–46 nm) were too small to form visible structural colors on glaze surfaces. Only “opal effect” was formed by the light scattering, which added the aesthetic feeling for the Ru celadon. Besides, the phase separation droplets intensified the segregation of iron, and thus deepened the chemical color and made the Ru celadon glaze appear green-blue. Due to the neutral to alkaline soil at the Ru Guan kiln site, the water in the soil and its corrosion on the Ru celadon glaze resulted in the formation of Si–OH bond.     

A PRELIMINARY STUDY OF THE RESISTANCE TO ABRASION OF CERAMIC GLAZES,ITS CONTROL AND METHODS OF DETERMINATION1

Two test methods, one using an Ingersoll glarimeter to obtain results of a high degree of accuracy, and the other simpler “alternate method” for plant control, are described in detail. Tests on commercial hotel chinaware showed the average resistance of foreign ware was higher than that of the domestic and the variation from the average was, in general, less. Experimental glazes were prepared to study the effect on resistance, of: (1) varying SiO₂ and Al₂O₃ content, (2) glaze thickness, and (3) firing treatment. Data obtained are insufficient to justify definite conclusions regarding the effect of varying SiO₂ and Al₂O₃, but do show the resistance of well-matured glazes to be inversely proportional to thickness, a decrease in resistance as the tendency to matt increases, a markedly increased resistance by the higher glost fire. That type of body affects resistance less than do glaze composition and temperature of glost fire.     

Zircon-free frits suitable for single fast-firing opaque wall tile glazes and their industrial productions

Wall tile glazes with a smooth surface texture, high glossiness, and whiteness are usually based on zirconium containing frits. However, these frits are quite expensive and therefore, there have recently been certain attempts to lower the production cost such as taking suitable glass–ceramic glaze systems into an account. With the present work, the frit-based glaze compositions belonging to the K₂O–MgO–CaO–ZnO–Al₂O₃–B₂O₃–SiO₂ glass–ceramic system were studied to prepare newly synthesized wall tile glazes for industrial single fast-firing. The design of a glass–ceramic glaze for this type of tiles should ensure that the selected frit precursor is technically and commercially compatible with the manufacturing conditions generally used in the production of glazed ceramic wall tiles. The aim of the study is to develop zircon-free, frit-based, glossy opaque glass–ceramic glazes for wall tiles by optimizing the CaO/MgO and adjusting the Al₂O₃/alkali ratios in the starting frit compositions. Frit production, glaze preparation, application, and single fast-firing of wall tiles were, first of all, conducted under laboratory working conditions and then, successful recipes were adapted to the relevant industry. The frit crystallization capability and crystallization temperature range were determined by differential thermal analysis (DTA). Thermal expansion coefficient values of glazes were determined by a dilatometer. Characterization of single fast-fired glass–ceramic glazes was made by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) techniques. Colour and gloss analyses of the final glazes were measured with a spectrophotometer and a gloss meter, respectively.