The study of crystal-phase composition and pore structure for Dicaoqing-Zisha compared with porcelain and pottery

Abstract

In China's long history tea culture, Zisha ceramic, from Yixing city, Jiangsu province of China, has been widely accepted as the optimum vessel for tea brewing. Zisha ceramic has existed for a millennium, but there are seldom studies that explore the composition and structure of this traditional ceramic. In this work, Dicaoqing-Zisha, a typical Zisha, is investigated as a representative. The results reveal that the Dicaoqing clay is natural composited clay and is very rich in Fe2O3. After fired at 1180 °C, Dicaoqing-Zisha is achieved with 33.2 wt% quartz, 32.8 wt% mullite, 3.2 wt% cristobalite, 5.9 wt% hematite, and 24.9 wt% amorphous phase. The percentages of mullite and cristobalite in Dicaoqing-Zisha are close to that in porcelain and much higher than that in pottery (an ordinary earthen pot). At the same time, the amorphous phase percentage of Dicaoqing-Zisha is in between that of porcelain and pottery. Compared with porcelain and pottery, the Dicaoqing-Zisha has specific pore structure including the highest specific surface area, middle porosity (larger than porcelain, but smaller than pottery), even distribution, and two main classes of pores: one is about 0.2 μm in diameter and the other is < 10 nm in diameter. We propose that Zisha is like pottery and yet not pottery, it is similar to porcelain but not porcelain. “Zisha” should be a specific name.