Zirconia-toughened glass ceramics

Abstract

ZrO 2 -toughened glass ceramics having high molar fractions of tetragonal ZrO2 and fracture toughness value of greater than 2 MPa·m 1/2 . The glass ceramic may also include also contain other secondary phases that may be beneficial for toughening or for strengthening through an ion exchange process. Additional second phases may also decrease the coefficient of thermal expansion of the glass ceramic. A method of making such glass ceramics is also provided.

1 . A glass ceramic or precursor glass comprising at least about 50 mol % SiO 2 , at least about 20 mol % Li 2 O, up to about 5 mol % Al 2 O 3 , and at least about 4 mol % ZrO 2 , wherein the glass ceramic comprises a tetragonal ZrO 2  phase, a crystalline lithium disilicate phase, and a residual glass phase, and wherein the glass ceramic has a contrast ratio of at least 60, and the lithium disilicate is the predominant crystalline phase and the tetragonal ZrO 2  phase is a minor crystalline phase. 
     
     
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         6 . The glass ceramic of  claim 1 , wherein the glass ceramic comprises about 5 to 60 vol % lithium disilicate and 1 to 20 vol % tetragonal ZrO 2  phase. 
     
     
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         11 . The glass ceramic of  claim 1 , wherein the crystal size of the tetragonal ZrO 2  phase is between 0.1 to 10 μm 
     
     
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         20 . The glass ceramic of  claim 1 , wherein the glass ceramic has a contrast ratio of 60 to 90. 
     
     
         21 . The glass ceramic of  claim 1 , wherein the glass ceramic has a fracture toughness of at least 3 MPa·m 1/2 . 
     
     
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         25 . The glass ceramic of  claim 1 , wherein the glass ceramic has a biaxial flexural strength equal to or greater than 300 MPa. 
     
     
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         28 . The glass ceramic of  claim 1 , wherein the glass ceramic has a chemical solubility equal to or less than 2000 μg/cm 2 . 
     
     
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         30 . The glass ceramic of  claim 1 , wherein the glass ceramic comprises 5.5-8.5 mol % ZrO 2 . 
     
     
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         34 . The glass ceramic of  claim 1 , wherein the SiO 2 :Li 2 O ratio is between about 1.8 to 3.0. 
     
     
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         39 . The glass ceramic of  claim 1 , wherein the glass ceramic comprises: from about 50 mol % to about 75 mol % SiO 2 ; from 0 mol % to about 5 mol % Al 2 O 3 ; from about 20 mol % to about 40 mol % Li 2 O; from 0 mol % to about 5 mol % Na 2 O; from 0 mol % to about 5 mol % of at least one alkaline earth oxide; from 0 mol % to about 5 mol % of at least one rare earth oxide; from about 4 mol % to about 15 mol % ZrO 2 . 
     
     
         40 . The glass ceramic of  claim 39 , wherein the glass ceramic comprises at least one of: from 0 mol % to about 5 mol % MgO; from 0 mol % to about 1 mol % Y 2 O 3 ; from 0 mol % to about 5 mol % CeO 2 ; and from 0 mol % to about 10 mol % TiO 2 . 
     
     
         41 . The glass ceramic of  claim 1 , wherein the glass ceramic comprises less than 2 mol % Al 2 O 3 . 
     
     
         42 . The glass ceramic of  claim 1 , wherein the wherein the glass ceramic further comprises at least one of a monoclinic ZrO 2  phase and a cubic ZrO 2  phase. 
     
     
         43 . The glass ceramic of  claim 1 , wherein the glass ceramic further comprises a monoclinic ZrO 2  phase, and wherein (tetragonal-ZrO 2  (wt %)/monclinic-ZrO 2  (wt %))≥2. 
     
     
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         51 . A glass ceramic comprising a tetragonal ZrO 2  phase, a crystalline lithium disilicate phase, and a residual glass phase, wherein the glass ceramic comprises: from about 50 mol % to about 75 mol % SiO 2 ; from 0 mol % to about 5 mol % Al 2 O 3 ; from about 20 mol % to about 40 mol % Li 2 O; from 0 mol % to about 5 mol % Na 2 O; from 0 mol % to about 5 mol % of at least one alkaline earth oxide; from 0 mol % to about 5 mol % of at least one rare earth oxide; from about 4 mol % to about 15 mol % ZrO 2 . 
     
     
         52 - 71 . (canceled) 
     
     
         72 . The glass ceramic of  claim 51 , wherein the glass ceramic forms at least a portion of a dental composite, a dental restorative, or a dental article. 
     
     
         73 . The glass ceramic of  claim 51 , wherein the dental article is one of a filling, a bridge, a splint, a crown, a partial a crown, a denture, a tooth, a jacket, an inlay, an onlay, a facing, a veneer, a facet, an implant, a cylinder, an abutment, framework or a connector. 
     
     
         74 . A method of making a glass ceramic, the glass ceramic comprising a residual glass phase, a tetragonal ZrO 2  phase dispersed throughout the residual glass phase, and at least one of a crystalline lithium disilicate phase, the method comprising the steps of:
 a. providing a precursor material, the precursor material comprising at least about 20 mol % Li 2 O, between about 55-65 mol % SiO 2 , and at least about 5 mol % ZrO 2 ,   b. ceramming the precursor material to form the glass ceramic, wherein ceramming comprises heating the precursor material at a first temperature for a first time period of from about 5 minutes to about 2 hours, followed by heating to a second temperature for a second time period of from about 5 minutes to 2 hours, wherein the first temperature is in a range from about 450° C. to about 750° C. and the second temperature is in a range from about 800° C. to about 900° C.   
     
     
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         82 . The method of  claim 74 , further comprising the steps nucleation, crystallization and sintering of the precursor glass powder. 
     
     
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         86 . The method of  claim 74 , further comprising machining or shaping the glass precursor material following heating the precursor material at the first temperature and prior to heating the precursor material at the second temperature. 
     
     
         87 . (canceled)