Porcelain is a ceramic material made by heating clay-type materials to high temperatures. It includes clay in the form of kaolinite

The ceramics industry of the Song dynasty (960-1279) pursued advances in kiln technology. Craftsmen searched far and wide for fine, new clays and exotic glaze colors, always looking for innovative ways of creating their wares. The kiln facilities, molding techniques, and spectrum of glaze colors grew increasingly versatile. The fiery spirit and determination exhibited by potters back then even rival the thirst for experimentation found among modern-day artists. [Source: National Palace Museum, Taipei npm.gov.tw]

The government in the Song as well as Yuan dynasty (1271-1368) earnestly sponsored the production of porcelains. Besides providing for objects of daily life, the imperial court also specified forms, production techniques, and raw materials for its ceramics, resulting in the rapid spread of kilns throughout the land that produced advanced porcelains.

Source: http://factsanddetails.com/china/cat2/4sub9/entry-5480.html