Patent ID: 6034011
Filing Date: 2000-03-07
Classification: C03C

Abstract:
A method for manufacturing a glass-ceramic substrate for a magnetic head, said glass-ceramic substrate having as its predominant crystal phase a mixed crystal of lithium disilicate (Li.sub.2 O.2SiO.sub.2) and either or both of .alpha.-quartz (.alpha.-SiO.sub.2) and .alpha.-cristobalite (.alpha.-SiO.sub.2), said .alpha.-quartz having a globular grain structure each globular crystal grain being made of aggregated particles and having a grain diameter within a range from 0.1 .mu.m to 3.0 .mu.m, said .alpha.-cristobalite having a globular grain structure each globular grain having a grain diameter within a range from 0.1 .mu.m to 1.0 .mu.m, said method comprising steps of subjecting to heat treatment a base glass comprising in weight percent: SiO.sub.2 65-83% Li.sub.2 O 8-13% K.sub.2 O 0-7% MgO + ZnO + PbO 0.5-5.5% in which MgO 0.5-5.5% ZnO 0-5% PbO 0-5% P.sub.2 O.sub.5 1-4% Al.sub.2 O.sub.3 0-7% As.sub.2 O.sub.3 + Sb.sub.2 O.sub.3 0-2%  at a nucleus forming temperature within a range from 400.degree. C. to 600.degree. C. for one to ten hours and further subjecting the glass to heat treatment at a crystallization temperature within a range from 650.degree. C. to 820.degree. C. for one to ten hours, and thereafter polishing the surface of the substrate to a surface roughness (Ra) of 5 .ANG. to 50 .ANG..