Strengthened glass and methods for making using differential chemistry

An article of manufacture, the article comprising:

• a chemically strengthened substrate characterized by having a glass chemical structure including alkali ions situated in the glass chemical structure
• wherein the substrate has dimensional volumes including
• a treatment-rich volume including a rich surface of the substrate,
• a treatment-poor volume including a poor surface of the substrate and characterized by having a variation from the treatment-rich volume in at least one of a chemical composition and a chemical structure, and
• a bulk volume, within the substrate, adjacent at least one of the treatment-rich volume and the treatment-poor volume,
• wherein a concentration of metal in at least one of the treatment-poor volume and the treatment-rich volume is ≧about 0.4 mole % higher than a concentration of the metal in the bulk volume,
• wherein a concentration of the metal is higher in the treatment-poor volume than a concentration of the metal in the treatment-rich volume, and
• wherein a concentration of alkali ions in a diffusion depth of at least one of the treatment-rich volume and the treatment-poor volume is ≦about 0.5 mole % higher than a concentration of the alkali ions in the bulk volume.

An article of manufacture, the article comprising:

• a chemically strengthened substrate made by a process including
• providing a substrate characterized by having
• a glass chemical structure comprising host alkali ions having an average ionic radius situated in the glass chemical structure, and
• wherein the substrate has dimensional volumes including a treatment-rich volume and a treatment-poor volume located as opposed to each other in the substrate,
• providing an exchange medium including a composition including invading alkali ions having an average ionic radius that is larger than the average ionic radius of the host alkali ions
• wherein the composition is associated with an ion exchange rate of the invading alkali ions,
• providing a modified exchange medium including a modified composition including invading alkali ions
• wherein the modified composition is associated with a modified ion exchange rate of the invading alkali ions and
• wherein the modified ion exchange rate is slower than the ion exchange rate,
• applying the modified exchange medium to a surface of the treatment-rich volume;
• applying the exchange medium to a surface of the treatment-poor volume;
• and
• conducting ion exchange while applying at least one of the exchange medium and the modified exchange medium to produce the strengthened substrate.