Method for manufacturing alkali-free glass substrate and alkali-free glass substrate

A method for manufacturing an alkali-free glass substrate, comprising:

• a batch preparing process of preparing a raw material batch so as to obtain alkali-free glass having a strain point of 700° C. or more;
• a melting process of melting the prepared raw material batch in a melting furnace;
• a fining process of fining the molten glass;
• and
• a forming process of forming the fined glass into a sheet shape, wherein the raw material batch is melted such that a bubble enlarging temperature of the obtained glass is lower than a maximum temperature of the fining process,
• wherein during the melting process electricity is supplied to the prepared raw material batch by applying electricity between a plurality of electrodes arranged on a bottom wall of the melting furnace and the prepared raw material batch is melted by Joule heat thereof, and
• the alkali-free glass contains, in mass %, 50 to 80% of SiO2, 15 to 30% of Al2O3, 0 to 4.5% of B2O3, 0 to 10% of MgO, 0 to 8% of CaO, 0 to 10% of SrO, 0 to 15% of BaO, 0 to 5% of ZnO, 0 to 5% of ZrO2, 0 to 5% of TiO2, 0 to 15% of P2O5 and 0 to 0.5% of SnO2 as a glass composition.