Patent ID: 8563454

Claim:
A fused and cast refractory product comprising, in mass percentages on the basis of the oxides and for a total of 100% of the oxides: ZrO 2 + Hf 2 O: balance to 100%; SiO 2 : 7.0% to 11.0%; Al 2 O 3 : 0.2% to 0.7%; Na 2 O + K 2 O: <0.03%; B 2 O 3 : 0.3% to 1.5%; CaO + SrO + MgO + ZnO + BaO: <0.4%; P 2 O 5 : <0.15%; Fe 2 O 3 + TiO 2 : <0.3%; Other oxide species: <1.5%; and the mass content of a dopant selected from Nb 2 O 5 , Ta 2 O 5 and mixtures thereof being of less than or equal to 1.0%, wherein an A/B ratio of Al 2 O 3 /B 2 O 3 mass contents is less than or equal to 2.0, and fused and cast products as a block of 220×450×150 mm 3 or a cylindrical bar of a diameter of 30 mm and a height of 30 mm, having the following chemical composition, in mass percentages on the basis of the oxides: ZrO 2 SiO 2 B 2 O 3 Al 2 O 3 Nb 2 O 5 Ta 2 O 5 Y 2 O 3 BaO 91.1 7.5 0.6 0.44 0.17 0.13 90.0 8.1 0.41 0.54 0.74 0.20 89.8 8.4 0.48 0.44 0.66 0.20 89.3 8.9 0.49 0.47 0.71 0.20 88.6 9.3 0.54 0.50 0.76 0.20 0.13 87.6 10.2 0.53 0.53 0.80 0.19 0.10 87.4 10.8 0.89 0.54 0.20 0.18 0.03 are excluded.