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We report on the analysis of dendritic crystals present in the dark spot areas of blue‐and‐white Ming porcelains. Using Raman spectroscopy and scanning electron microscopy equipped with energy dispersive spectrometer, we were able to evidence Mn‐rich spinels. Small Mn‐based spinel crystals being highly sensitive to laser‐induced heating, we identified proper working conditions, avoiding excessive heating and damage. Local temperatures during Raman measurements were deduced from Stokes/anti‐Stokes intensity ratios. By analysing the behaviour of the A1g mode of Mn‐rich spinels, we were able to identify phases ranging from jacobsite‐like to hausmannite‐like compounds. Polarized Raman scattering was shown to provide a convenient means of discriminating between these two types of phases, as they display different symmetries. Inhomogeneities within the dendritic network, as evidenced by micro‐Raman measurements, highlight its gradual formation during the cooling phase of firing, depending of Fe3+ and Mn3+ availability. The presence of Mn‐based spinels is consistent with the use of a local Chinese Mn‐rich cobalt ore during the middle Ming Dynasty.

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h i g h l i g h t sBES-BCO has the capability for efficient COD reduction, and AO7 decolorization. The decolorized products of azo dyes were further degraded in BES-BCO. The bioanode activity was inhibited at high DO concentration. The oxygen and AO7 competed as electron acceptor at BES unit.

Raman spectroscopy and scanning electron microscopy equipped with energy dispersive spectrometer (SEM‐EDS) were used to analyze the decors of the Yuan blue and white porcelains (Qinghua porcelains). SEM‐EDS carried out on the dark spots of the blue decors revealed the presence of dendritic crystals of a mix cobalt iron oxide. The Raman spectra of these crystals are close to the standard spectrum of cobalt ferrite (CoFe2O4). Comparing the Fe/Co ratios obtained by EDS to the corresponding Raman spectra, we have identified two main types of spinel crystals: one type richer in iron and another type richer in cobalt. Both types of spinel cause the blackening of the blue decors. It is the first time that spinel crystals with a composition close to cobalt ferrite were observed as the main constituent of the dark spots in blue decors of Qinghua porcelains. Copyright © 2016 John Wiley & Sons, Ltd.