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.     

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.     

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.     

Study on the copper and iron coexisted coloring glaze and the mechanism of the fambe

With copper and iron oxides as colorants, reddish and bluish purple glazes were prepared by changing the raw material ratio at the same firing schedule. Based on the primary factor experiments and the analyses of XRF and SEM/EDS, the fambe mechanism was proposed. The results indicated that glaze colors were related to multiple factors. The difference in copper red and purple glazes was merely caused by the later ingredient containing Ca₃(PO₄)₂, in which liquid-liquid phase separation structures were developed and formed structural colors, while the accumulated Fe₂O₃ in one phase decomposed to Fe²⁺ and bubbles to form blue stains and colorful texture. In addition, both CuO and Fe₂O₃ had a variety of coloring characteristics, which depended on the process parameter, firing temperature and base glaze compositions to make colors and hues change accordingly. In such cases, the multiple chemical colors were coupled with structural colors to form the fambe glaze.     

Mössbauer spectroscopy and neutron activation analysis of ancient Chinese glazes

The optical spectra of the glaze of Ru porcelain made in the Chinese Northern Song Dynasty (AD 960–1126) were measured by the chromatometer to determine the relations between glaze color and its dominant wavelength (λ_D). The concentrations of 30 coloring elements in the glaze were determined by neutron activation analysis (NAA). Iron was the dominant coloring element. Mössbauer spectroscopy detected that iron existed in the state of structural Fe²⁺ and Fe³⁺ ions. A relationship between λ_D of various colored glazes and the Fe²⁺/Fe³⁺ ratio was established. As the Fe²⁺/Fe³⁺ ratio gradually increases, the glaze color of Ru porcelain will gradually change from pea green to sky green. All the Ru porcelains were fired in a reducing atmosphere. The sky green Ru porcelain was fired in the most reducing atmosphere and at the highest temperature, the powder green in a more reducing atmosphere and at a lower temperature and the pea green in a lightly reducing atmosphere and at the lowest temperature.     

A HOME MADE JOLLEY

Molybdenum used as a colorant for glazes has a strong coloring power even though used in small percentages, affecting the glaze as R₂O₃. Both a bright yellow and a bluish green were secured.     

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.     

Chemical and microstructural comparison of the export porcelain from five different kilns excavated from Nanhai I shipwreck

Nanhai I shipwreck, a fully loaded merchant ship of the Southern Song Dynasty, once heading for the Southeast Asia, represents the prosperous international ceramic trades during that time. Recent excavation provides us with the great opportunity to investigate the export porcelain on this ship. Black Porcelain and green porcelain of Cizao kiln, white porcelain of Dehua kiln, bluish white porcelain of Jingdezhen kiln, celadon of Longquan kiln, and white porcelain of Minqing Yi kiln were analyzed chemically and morphologically by polarizing microscopy, energy dispersive X-ray fluorescence spectroscopy and scanning electron microscopy with energy dispersive spectroscopy. The chemical and microstructural features of each kind of porcelain, evidently different from each other, are discussed in detail in this paper. Among them, the Dehua white porcelain and the Jingdezhen bluish white porcelain may represent the best manufacture techniques for their purest glazes and bodies. Also, anorthite crystals are common in the calcium glazes of the Longquan celadon and the Jingdezhen bluish white porcelain. The most interesting structure among the samples observed is the structure of crystals and MgFe rich phase separation in the black glaze of Cizao porcelain, which is also different from other black glazes studied in previous research.     

Production and characterisation of iron-chromium pigments and their interactions with transparent glazes

In this study, production and characterisation of pigments by using less expensive raw materials such as limonite and chromite was undertaken. The resulting pigments were characterised by using X-ray diffraction (XRD) and UV-Vis spectrophotometer. The colour of glazed tiles containing 3 wt.% pigment change from dark brown to light brown depending on the calcination temperature and limonite content. With pigments prepared with 50% limonite content calcined at 1250 °C, the chocolate brown colour was obtained corresponding to the commercial brown pigments. An iron-chromium black pigment was synthesised from a mixture of pure chromium (III) oxide (Cr₂O₃) and iron (III) oxide (Fe₂O₃) powders and was used to determine possible interactions between a pigment and a transparent glaze. The interactions were studied using a scanning electron microscope (SEM) attached with an energy dispersive X-ray spectrometer (EDX). The results showed that black pigment particles give brown colour to the glaze. EDX analysis on pigment crystals embedded in the glaze clearly showed that Zn and Mg diffused into pigment crystals and caused a change of colour from black to brown.     

Angle dependence of Jian bowl color and its coloring mechanism

Jian bowl is generally known for its artistic appearance such as hare's fur and oil spots caused by the crystallization of iron oxides on the glaze surface. While very few Jian bowls have angle-dependent colors, scientific research on the topic is lacking owing to the scarcity of relevant samples. In this study, the angle-dependent colors of Jian bowls were systematically studied using various characterization techniques, such as angle-resolved reflectance spectra, X-ray diffraction, micro-Raman, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy and atomic force microscopy. The angle dependence phenomenon of Jian bowl colors was classified into two types, and the coloring mechanisms were clarified. The first type of coloring mechanism is assumed to be coherent light scattering by an amorphous photonic structure formed during the firing process, which has weak angle dependence. The second type of coloring mechanism is thin-film interference, which has obvious angle dependence and is closely related to the corrosion process of Jian bowls in the burial environment.     

Multi-micro analytical studies of blue-and-white porcelain (Ming dynasty) excavated from Shuangchuan island

Shangchuan Island lies in the southern part of the Guangdong Province in China. Historically it is considered as an important berthing wharf of the South China Sea for the Maritime Silk Roads, witnessing the early Sino-Portuguese trades. Related research on the cultural relics in the region has attracted significant attention from archaeologists. In this study, blue-and-white porcelains excavated from Shangchuan Island were analyzed by multi-micro analytical techniques. In-glaze decoration and under-glaze decoration processes were suggested for the glaze painting process, as revealed by digital microscopy. Silica-aluminum system with flux agents of calcium, potassium and sodium, as well as the main elements of blue pigment with iron, manganese, cobalt and nickel, were found by analysis of micro X-ray fluorescence spectrometry. By calculating the discriminate functions (F) for the chemical compositions of porcelains body, as well as the S_i value for porcelain glaze, the origin of these blue-and-white porcelains were identified with the origin of the Jingdezhen kiln in the Ming dynasty. Anorthite (CaAl₂Si₂O₈) crystals were observed in glaze layer of porcelain by micro-Raman spectroscopy, as well as α-quartz (SiO₂) and calcite. These archeological evidences not only helped to understand the history of the early Sino-Portuguese relations, but also proved the important historical status of Shangchuan Island and contributed to the study of the history of Chinese ancient Maritime Ceramic Road.     

陶瓷马赛克陨石花釉的研制

主要研究了以棕褐色底釉与灰白色面釉组合而成的花釉,该釉烧成后其花纹和颜色犹如陨石效果,用于马赛克的生产。文中主要讨论了底面釉化学成分、着色氧化物的含量、烧成制度、釉层厚度等因素对陨石花釉釉面效果的影响。     

Unveiling the science behind the tea bowls from the Jizhou kiln. Part II. Microstructures and the coloring mechanism

In this part of the study, optical microscope, field emission scanning electron microscope-energy dispersive spectrometer, transmission electron microscope-selected area diffraction-energy dispersive spectrometer, micro-Raman and reflectance spectrum were applied to further study the microstructures of the characteristic areas of the glazes and illustrate the coloring mechanism of the “hare's fur” tea bowls with blue or bluish violet patterns. The results show that due to the diffusion between the cover glaze and ground glaze caused by compositional difference, as well as the “boiling effect” of the ground glaze, local chemical composition changes to form the different microstructures in different regions. Large sized interconnected phase separation structure with approximately 350?nm characteristic size forms in the unreacted portion of the cover glaze, leading to the scattering of all wavelengths of the incident visible light. With the contribution of the ground glaze which has low immiscibility tendency, small sized interconnected phase separation structure with approximately 170?nm characteristic size forms at the edge of the white region, leading to the scattering of the blue light range of the incident visible light. The fluctuation of thermal history gives various appearance to the Jizhou “hare's fur” tea bowls, although they share the same coloring mechanism. In general, chemical composition, microstructure and firing schedule cooperate with each other to create the changeful appearance of the Jizhou tea bowls.     

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.     

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.     

Phase-separated Tenmoku “Blue” glaze: Microstructure and coloring mechanism

Yohen Tenmoku, a masterpiece of Jian kiln with bright blue rendering effect under different incident light, is lack research as only three intact pieces exist in the world. Herein, this study was fortunate to work with Jianxing Sun to conduct technical characterization and material analysis of the imitation Yohen Tenmoku (Song). Black oil spots are composed of magnetite (10–25 µm) and Al doping in hematite (1–3 µm) precipitated on the glaze surface. Brilliant blue color a combination of the bright blue structural color resulting from the coherent scattering of amorphous photonic crystals composed of spherical phase separation structures of 130 nm and the coloring of iron ions produced in a weak reducing atmosphere by the addition of high iron glazes with composite alkali (CaO and MgO). Continuous refraction and reflection of the structural color between the blue glass phases gives the glaze a shiny and dazzling blue color.     

Utilization of seashells in matte glaze preparation

In this study, the investigation of the optical properties and microstructural development of matte glaze compositions prepared with the addition of seashells was aimed. The seashells obtained from Black Sea beaches of Samsun, Turkey were characterized using XRF, XRD, FTIR, TG-DTA techniques, and heating microscope. The calcite-aragonite polymorphic transition was provided by heat treatment of seashell powders at 700°C for 1 hour and then, aragonite-based seashell powders were incorporated to matte glaze compositions up to 30 wt%. Firstly, four different types of fired body specimens (red clay, chamotte, white, and porcelain) were produced at 800ºC for 7 hour. Secondly, the prepared glazes were applied on surface of all fired bodies and then, all bodies were sintered at 1100ºC for 8 hour. Finally, coloring parameters and microstructural features of seashell added glazes were determined. The addition of seashells to glaze composition by 10 and 20 wt% resulted in higher transparency. The matte glaze was formed with increment of seashell content to 30 wt%. The more reduced fluidity of the glaze caused nonhomogenous matte appearance. As a result, it is possible to produce transparent glazes in eco-friendly and cost-effective way by addition of seashells into glaze composition in 20 wt%.     

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.     

Reproduction of Jun‐red glazes with nano‐sized copper oxide

Nano sized copper oxide was firstly employed for producing Jun‐red glazes. A series of Jun‐red glazes were prepared by adjusting the copper oxide nanoparticle content and the valance state of elemental copper in the glaze matrix. The coloring and microstructure of each glaze was investigated by spectrophotometer, X‐ray diffraction, scanning electron microscope, X‐ray photoelectron spectrometer, and transmission electron microscope. Under reducing conditions, the red glaze color gradually darkens with increasing CuO content from 0.5 to 1.0 wt%. Interestingly, the coloring of the samples fired under reducing atmosphere turned to be green‐blue, when the content of nanosized CuO was increased to 1.5 wt%. We also found that increased CuO content increases the size of phase separation in the glazes. As comparison, the coloring of samples fired without nanosized CuO are slightly blue under reducing atmosphere, which is attributed to the structural color generated owing to the Rayleigh scattering. Red color of the Jun glazes may arise from elemental copper nanoparticles. The current research utilizing modern nanotechnology provides a new insight into both the “furnace transmutation” and “color regulating” of the ancient Jun‐red glazes.     

Coloring effect of iron oxide content on ceramic glazes and their comparison with the similar waste containing materials

The effects of adding iron oxide to ceramic glaze formulations were studied in this study. Iron oxide was added in different weight ratios into the reactive transparent glaze, reactive opaque glaze, and transparent glaze formulations. The iron oxide content in the glaze composition, the coloring mechanisms, the phase distributions, and surface properties at temperatures of 950–1000-1050-1200 °C in the oxidation firing medium were investigated. Scanning Electron Microscopy (SEM) to determine the microstructural and morphological characterizations of the test glazes, X-Ray Diffractometry (XRD) to determine the crystallographic properties and phases, and X-Ray Fluorescence (XRF) analyses to determine the elemental and chemical composition were performed. In addition to these, surface images were examined with Digital Microscope (DM) and Commission Internationale de l'Eclairage (CIE) L*a*b, and water absorption values were compared. In addition, taking into account environmental factors, a comparison of ceramic glazes with the same amount of waste iron oxide was also performed for same purpose. As a result of the studies, it was observed that the addition of iron oxide and/or waste iron oxide did not have a negative effect, and coloring effects on the glaze layer were observed at different rates and firing temperatures.