data of celadon from Qingliangsi kiln and Zhanggongxiang kiln

The porcelain shreds were selected from the Baofeng Qingliangsi kiln and Ruzhou Zhanggongxaing kiln, among which 9 Ru ware and 5 Ru-type ware excavated from the central production area of Qingliangsi kiln, 19 Ru ware from the non-central production area of Qingliangsi kiln, and 31 celadon from Zhanggongxiang kiln. The experimental samples were provided by the Baofeng Ruyao Museum and Henan Provincial Institute of Cultural Heritage and Archaeology, respectively. The pictures of typical porcelain samples from the two kilns were shown in Fig. 1. ExperimentsThe cross-section structure of glaze layers was studied by non-destructive swept source optical coherence tomography (OCT, HSL-2100, Santec, Aichi, Japan), which consists of four separate parts: sweep source, interferometer unit, computer unit and OCT probe. The experiments were carried out in sweep mode. The central wavelength was around 1315~1340 nm, the spectral peak half-height width was 110 nm, the sweep frequency was 20 kHz, and the maximum laser power was 50 mW. The scanning range of OCT probe was 0-20 mm. In silicate materials, the largest transverse and longitudinal resolution is 5 μm/pixel and 5.3 μm/pixel, respectively. This OCT technique has been successfully applied to analyze the fracture structure of ancient Chinese porcelain and glass [18-21].Portable energy dispersive X-ray fluorescence spectrometer (PXRF, OURSTEX 100FA, OURSTEX, Osaka, Japan) was employed for the chemical components analysis. For this XRF instrument, standard samples (NIST 1411 and BR CH4), purchased from the Breitlander Eichproben und Labomaterial GmbH, Germany, were used for checking the precision and accuracy. A set of standard samples (22), were purchased from the Breitlander Eichproben und Labomaterial GmbH, Germany, containing most interested major and trace elements in silicate materials were applied for making the calibration curves for porcelain glaze. Meanwhile, a set of standard samples (13), provided by the Shanghai Institute of Ceramics, Chinese Academy of Sciences, China, were applied for making the calibration curves for the ceramic body. It was equipped with a low-vacuum sample chamber, which can effectively measure the content of light elements (such as F, Na) in air. The X-ray beam spot irradiated at the sample was about 2.5 mm in diameter, and more details can be found in the published articles. Similar equipment had already been applied in chemical composition analysis of ancient porcelain [22-24].X-ray diffractometer (XRD, D/max 2550V, Rigaku, Tokyo, Japan) equipped with filtered Cu Kα radiation (40 kV, 40 mA) was carried on glaze surface to acquire phase constituents (scanning speed: 2° min-1; scanning area: 10-90°). To accurately identify the phase information on crystals and base glaze, Raman spectra were collected at room temperature by confocal micro-Raman spectrometer (LRS, LabRAM XploRA, Horiba, Palaiseau, France) using a 532 nm excitation radiation source (300 mW).Optical microscopy fixed with an ultra-depth-of-field system (OM, VHX-50000, Keyence, Osaka, Japan) was applied for morphology observation. The microstructure and elemental analyses of porcelain samples (both surfaces and cross-sections) were conducted by scanning electron microscopy (SEM) configured with energy-dispersive X-ray spectrometer (EDS) operated in the backscattered electron image mode (SEM, S-4800, HITACHI, Tokyo, Japan). Some selected nanostructures were characterized by a high resolution transmission electron microscopy at 200 kV (TEM, Tecnai G2 F20 S-TWIN, Hillsboro, America). Several glaze lamellas of 10 μm x 10 μm and 100 nm thick were cut, thinned, extracted and polished by focused ion beam (FIB) method. Typically, in this work, SEM and TEM samples was not etched in hydrofluoric (HF) acid solution. The glaze color of samples was analyzed by chromatic spectrophotometer (NS 800, Shenzheng, China). This instrument adopts the combined LED precision spectroscopy, which has higher accuracy and is sensitive to any color. In addition to measuring Lab and dE values, it can directly display the spectral reflectance curves (400~700 nm). The color characteristic parameters in this research were the average of three tests.