Strengthened glass and methods for making using heat treatment

An article of manufacture, the article comprising:

• a strengthened substrate, having a width ≦ about 25.0 millimeters and a compressive stress layer having a depth of about 1-500 μm, characterized by having a glass chemical structure including alkali ions situated in the glass chemical structure and 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 strengthened substrate, including a compressive stress layer having a depth of about 1-500 μm, made by a process including
• providing a substrate, having a width ≦ about 25.0 millimeters, characterized by having a glass chemical structure including host alkali ions having an average ionic radius situated in the glass chemical structure and dimensional volumes including a treatment-rich volume and a treatment-poor volume located as opposed to each other in the provided substrate;
• heating the provided substrate to a heat-treating temperature ≧ about 250° C. and ≦ a maximum heat-treating temperature for a heat-treating period of about 0.01-20 hours, wherein if the heat-treating temperature is ≦ about 325° C., then the heat-treating period is ≧ about 2 hours, to produce a heat-treated substrate;
• providing an exchange medium including invading alkali ions having an average ionic radius that is larger than the average ionic radius of the host alkali ions;
• exposing the heat-treated substrate to the exchange medium;
• and
• conducting ion exchange while exposing the heat-treated substrate to the exchange medium to produce the strengthened substrate.