2016 年 80 巻 5 号 p. 326-333
The microstructure of the stucco surface containing Pb of the Takamatsuzuka tumulus, constructed in the 7th-8th century, has been investigated. The purpose of this research is to clarify the existing condition of Pb near the stucco surface. A spectro-reflectometer, a scanning electron microscope, and a transmission electron microscope are used to analyze the microstructure. The surface of the specimen consists of three colored areas; white, dull ocher, and ocher. Although the absorption edges of the white stucco CaCO3 and ocher area on the surface are approximately 2.8 and 2.0 eV respectively, the dull ocher area does not show the absorption edge. The latter absorption edge is caused by Fe ion contained in the surface layer. The dull ocher area is rich in Pb. The surface layer consists of fine lead carbonate grains with a size of 100-200 nm. On the layer under the surface layer, CaCO3 grains containing lead oxide precipitates, that is, Pb3O4 and Pb2O3, and CaCO3 grains containing Pb atoms are observed. The size of the lead oxide in CaCO3 is 10-500 nm. These grains are formed by the reaction between the lead carbonate and the CaCO3 matrix. It is thought that the lead carbonate is coated on the stucco.
