| Celadon is the origin of Chinese porcelain.Meanwhile,the development of Chinese porcelain from primitive to mature is also represented by the celadon.In the ancient Chinese celadon history,there are Yue kiln,Yaozhou kiln,Ru kiln,Guan kiln and Longquan kiln,which play important roles in the Northern and Southern kilns.For Yaozhou celadon in the Five dynasty,the white body ware is bright and translucent,and the black body ware is elegant and moist.It could be regarded as the best celadon of the Yaozhou kiln in all dynasties.For Ru celadon in the Northern Song dynasty,the sky-green ware is good,and the pink-green ware comes second.Furthermore,the sky-blue ware is particularly precious.Ru kiln is the first of the "the five famous kilns" in the Song dynasty.For the Guan celadon in the southern Song dynasty,the pink-green ware is best,and the black body is most.Besides,it has characteristics of crab claw patterns,mouth-rim and foot-rim of purple or iron color,as well as has a special aesthetic feeling of warm and moist of the Southern celadon.Although celadons of different dynasties and kilns are mainly colored by iron contained in mineral raw materials,their tone and texture vary greatly,and the regional characteristics are obvious.Therefore,it is not only the need of excavating the scientific value of cultural relics and identifying their characteristics,but also the important reference for the traditional ceramic industry to explore the preparation process and technology,the coloring mechanism and the science essence of artistic appearance.In order to clarify common and key scientific problems of celadon and the essential reasons of color difference and regional characteristics formation,this work intends to investigate the sky-green ware of the Five dynasty Yaozhou kiln,while comparative analyze core elements and characteristic elements in chemical compositions,microstructures of body and glaze,process and technology condition of Ru ware in the Northern Song dynasty and Guan ware of the Southern Song dynasty.The results were as follows:(1)The glaze color of Yaozhou ware in the Five dynasty was affected by the chemical color produced by iron element and the color of phase separation structures,which made it present beautiful and charming sky-green.Furthermore,dense phase separation structures formed opacifying effect by the scattering of natural light and added the beauty of warm and mild to the glaze.In the white body,low contents of Fe2O3 and ferrotitanium solid solution greatly decreased the absorption of incident light.Meanwhile,small amount of grain boundaries and pores also weakened the scattering of incident light.As the result,Yaozhou ware has the higher light transmittance.However,the content of Fe2O3 in white body was higher than 1.0 wt%,which made its transmittance only under strong light and not obvious.(2)In the Ru ware glaze of the Northern Song dynasty,a large number of bubbles and anorthite crystals formed special glossiness and opacifying effect.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 the obvious structural color on glaze surfaces.Only "opal effect" was formed by the light scattering,which added individual aesthetic feeling for the Ru ware.At the same time,phosphorus promoted the widespread formation of phase separation droplets and intensified the segregation of iron,and thus deepened the chemical color and made the glaze color of Ru ware appear green-blue.In addition,the Ru ware glaze contained Si-OH bond,which was due to the neutral to alkaline soil at the kiln site.During the long burial process,the water in the soil and its own corrosion on the glaze surface resulted in the formation of Si-OH bond.(3)In the Guan ware glaze of the Southern Song dynasty,there were a large number of bubble aggregations on the glaze surface,which surround by the quartz crystal.This was because the supersaturated melt near quartz particles discharged gas during the melting process,and continuously formed new bubbles,which then diffused into existing bubbles,resulting in the structure.The formation of bubble aggregations did not affect the glaze color of the Guan ware,but it could improve the opacity of the glaze surface by the light scattering.Moreover,the Guan ware glaze had a high SiO2/Al2O3 molar ratio(8.760-11.451 mol%),so liquid-liquid phase separation structures were formed.Due to the high density and the size of the separated phase droplets only 21-30 nm,the structural color was weak,and the separated phase droplets only 21-30 nm,the structural color was weak,and thus the glaze color was mainly determined by the chemical color produced by iron ions.In addition,phase separation droplets,bubbles and anorthite crystals could improve the jade-like texture of glaze and modify the glaze color.(4)The comparative analysis of celadon glazes from the Five dynasty Yaozhou kiln,Northern Song dynasty Ru kiln and Southern Song dynasty Guan kiln showed that the celadon glaze of the Five dynasty Yaozhou kiln contained the highest contents of K2O and CaO,which was beneficial to the formation of green-blue color and the growth and discharge of bubbles in the glaze layer.As a result,the glaze was green-blue with high transparency and glossiness.The celadon glaze of the Northern Song dynasty Ru kiln contained the highest contents of Fe2O3 and P2O5.P2O5 could promote the phase separation of ware glaze,causing the segregation of iron element and deepening the green-blue of Ru ware glaze.In addition,the dense bubbles,crystals and phase separation structures in the glaze increased the opacity and formed the opal effect of the Ru ware glaze.The base glaze composition of the Southern Song dynasty Guan kiln celadon was similar to that of the Ru kiln,and their micro structures were also similar.However,higher SiO2 content promoted the formation of bubble aggregations in the heterogeneous nucleation stage of glaze,which further improved the opacity and was conducive to the formation of texture properties of jade.In addition,The differences of firing temperature,pH value of buried soil and iron state in the raw material also affected the appearance of celadon glazes and formed regional features.(5)Ca3(PO4)2 was used instead of the glaze ash as the phase separation promoter to study its action mechanism on the Fe2O3 colored glaze.The results indicated that with the addition of Ca3(PO4)2,CO2+ and P5+ with highly-active were introduced into the glaze.Since Ca2+ with high ionic potential(Z/r=1.89)had a greater ability to appeal O2-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 round glaze patterns.Adding P5+ that had a strong effect of reversed polarization on the Fe-O increased contents of Fe2+ and Fe3+-O-Fe2+,and thus deepened blue-green of glaze surface.In addition,it promoted the formation of worm-like phase-separated structures.They not only formed the amorphous structural color by the Bragg scattering,but also affected the distribution and chemical state of the iron element,thus affecting the chemical color.The coupling effect of structural color and chemical color further deepened the blue tone of glaze. |
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