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Abstract

This invention is directed at the makings of glass-ceramic which is uniquely suited for use as a disc substrate for utilization in a magnetic memory storage device. The glass ceramic material exhibits a crystal phase assemblage comprised predominately of a mixture of lithium disilicate and tridymite which are uniformly interspersed with a residual glass phase and form an interlocked microstructure with the glass. The composition consists essentially, expressed in terms of weight percent on the oxide basis, of 75-95% SiO.sub.2, 3-15% Li.sub.2 O, 0-6% Al.sub.2 O.sub.3, and 0-6% K.sub.2 O. The nucleating agent for this glass-ceramic is selected from the group consisting of 0-0.1% Pd and 0-5% P.sub.2 O.sub.5 ; however if Pd is absent the P.sub.2 O.sub.5 amount is at least 0.5% and if P.sub.2 O.sub.5 is absent then the Pd amount is at least 0.005%. Additionally, up to 15% of optional ingredients may be added, including, B.sub.2 O.sub.3, Na.sub.2 O, ZnO, MgO, CaO, SrO, ZrO.sub.2, TiO.sub.2, F, Sb.sub.2 O.sub.3, As.sub.2 O.sub.3, PbO and BaO.

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First Claim