Doped titanate glass-ceramic for grain boundary barrier layer capacitors
AssigneeInternational Business Machines Corporation
InventorsDudley A. Chance, Yung-Haw Hu
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Abstract
A high dielectric constant glass-ceramic material comprising small conducting grains based on BaTiO.sub.3 and/or SrTiO.sub.3 on the order of about 0.5-10.0 .mu.m surrounded by a thin microcrystalline insulating barrier layer at the grain boundary about 0.01-0.10 .mu.m thick wherein the conductivity of the grains is enhanced by addition of about 0.1-4.0 mol % of a dopant selected from among Group V elements, Ge and Si substantially incorporated in the bulk lattice of the grains upon Ti sites. A novel process for forming the glass-ceramic material is also disclosed.
Claims23
A high dielectric constant glass-ceramic material comprising small conducting grains based on BaTiO.sub.3 and/or SrTiO.sub.3 on the order of about 0.5-10.0 .mu.m surrounded by a thin microcrystalline insulating barrier layer at the grain boundary about 0.01-0.10 .mu.m thick wherein the conductivity of the grains is enhanced by addition of about 0.1-4.0 mol% of a dopant selected from among Group V elements, Ge and Si substantially incorporated in the bulk lattice of the grains upon Ti sites.
A method for producing a high dielectric constant glass-ceramic material comprising:
- (a) admixing about 40-65 total wt % BaO and/or SrO, about 20-35 wt % TiO.sub.2, about 0.1-4.0 wt % of a dopant selected from among Group V elements, Ge and Si, about 10-15 wt % SiO.sub.2, about 6-12 wt % Al.sub.2 O.sub.3, about 0-2 wt % MgO, and about 0-3 wt % Li.sub.2 O, by a powder mixing process to obtain a homogeneous powder mixture;
- (b) melting the powder mixture in a crucible or like vessel at a temperature of about 1500.degree. to 1600.degree. C. for about 1 to 4 hours to form a melt;
- (c) quenching the melt by pouring it on a quench plate or into water to form glass cullets;
- (d) crushing the glass cullets to obtain a powder mixture sufficiently fine to pass through a 325 mesh screen;
- (e) admixing the powder mixture for about 10 to 30 hours to obtain a dry glass powder mixture of average particle size of about 2 to 7 .mu.m;
- (f) pressing the dry glass powder in a die at a pressure of about 5,000-15,000 lbs. to obtain a green compact;
- (g) firing the green compact to sintering temperatures sufficient to accomplish sintering or coalescence of glass particles and conversion to a glass-ceramic by crystallization.
Dependencies are inferred from the claim text.