Patent ID: 8347650

Claim:
A method of producing a quartz glass crucible for pulling a single crystal, the method comprising: a. providing a melting mold comprising a wall having an inside, an outside and passages between the outside and inside; b. providing an outer layer granulation of first SiO 2 particles, and forming an outer granulation layer from the outer layer granulation on the inside of the melting mold wall; c. providing a barrier layer granulation of second SiO 2 particles, said second SiO 2 particles being finer than the first SiO 2 particles, and forming a barrier granulation layer from the barrier layer granulation on the outer granulation layer; d. applying a negative pressure to the outside of the melting mold wall; e. heating the barrier granulation layer and the outer granulation layer so as to form the quartz glass crucible with a transparent inner layer; wherein the SiO 2 particles of the barrier layer granulation have a D 50 value of less than 50 μm and wherein the formation of the barrier granulation layer includes fixing the barrier layer granulation to the outer granulation layer; wherein the fixing of the barrier layer granulation comprises wetting the barrier granulation layer with a liquid; wherein the heating comprises a two-stage heating process, including a first heating stage during which the barrier granulation layer is vitrified at a low temperature, and a second heating stage during which the outer granulation layer is heated at an elevated temperature higher than said low temperature and thereby sintered at least in part; and wherein the granulation barrier layer is formed so as to have a thickness of less than 3 mm.