Glass ceramic having specific thermal expansion characteristics

1 . LAS glass ceramic having an average coefficient of thermal expansion CTE in the range from 0 to 50° C. of not more than 0±0.1×10 −6 /K and thermal hysteresis at least within the temperature range from 10° C. to 35° C. of <0.1 ppm, and a main crystal phase of a high quartz solid solution, and comprising the following components (in mol % based on oxide):

SiO 2

60-71  

Li 2 O

7-9.4 

MgO + ZnO

0-<0.6

at least one component selected from the group consisting of P 2 O 5 , R 2 O, and RO, where R 2 O may be Na 2 O and/or K 2 O and/or Cs 2 O and/or Rb 2 O, and where RO may be CaO and/or BaO and/or SrO, and

a nucleating agent in a content of 1.5 to 6 mol %, where the nucleating agent is at least one component selected from the group consisting of TiO 2 , ZrO 2 , Ta 2 O 5 , Nb 2 O 5 , SnO 2 , MoO 3 , WO 3 , and HfO 2 ,

wherein the LAS glass ceramic contains not more than 0.05 mol % of As 2 O 3 as a refining agent.

2 . LAS glass ceramic according to claim 1 , further containing Al 2 O 3 in a content of 10 to 22 mol % and/or P 2 O 5 in a content of 0.1 to 6 mol %.

3 . LAS glass ceramic according to claim 1 , wherein the content of the sum of ZnO+MgO is ≤0.55 mol % and/or the content of MgO is ≤0.35 mol % and/or the content of ZnO is ≤0.5 mol %.

4 . LAS glass ceramic according to claim 1 , wherein the content of the sum of ZnO+MgO is ≤0.5 mol %.

5 . LAS glass ceramic according to claim 1 , wherein the content of the sum of RO is ≥0.1 mol % and/or ≤6 mol %.

6 . LAS glass ceramic according to claim 1 , wherein the content of the sum of R 2 O is ≥0.1 mol % and/or ≤6 mol %.

7 . LAS glass ceramic according to claim 1 , wherein the content of the sum of the nucleating agent is ≥2 mol % and/or ≤5 mol %.

8 . LAS glass ceramic according to claim 1 , wherein the following condition is applicable: molar content of SiO 2 +(5× molar content of Li 2 O)≥106 and/or wherein the following condition is applicable: molar content of SiO 2 +(5× molar content of Li 2 O)≤115.5.

9 . LAS glass ceramic according to claim 1 , wherein a processing temperature Va is not more than 1330° C.

10 . LAS glass ceramic according to claim 1 , wherein the high quartz solid solution has an average crystallite size of <100 nm, and/or a crystal phase content is less than 70% by volume.

11 . LAS glass ceramic according to claim 1 , wherein an index F is <1.2, where F=TCL (0; 50° C.)/|expansion (0; 50° C.)|, wherein the index F is calculated by forming a quotient of TCL (0; 50) [in ppm] and a difference in expansion between temperature points of 0° C. and 50° C. [in ppm];

wherein TCL is a distance between a highest dl/10 value and a lowest dl/10 value within the temperature points and TCL (0; 50° C.)=|dl/l 0 max.|+|dl/l 0 min.|; and

where “dl” denotes a change in length at a respective temperature and “l 0 ” a length of a test specimen at 0° C. and the calculation is based in each case on absolute values of the dl/l 0 values.

12 . LAS glass ceramic according to claim 1 , wherein an alternative index f (20; 40) is <0.024 ppm/K and/or an alternative index f (20; 70) is <0.039 ppm/K and/or an alternative index f (−10; 30) is <0.015 ppm/K, wherein an alternative index f T.i. (ppm/K) is defined as f T.i. =TCL (T.i.) /width of a temperature interval (T.i.), wherein T.i. describes a considered temperature interval in each case;

wherein TCL (T.i.) is a distance between a highest dl/l 0 value and a lowest dl/l 0 value within a considered temperature range (T.i.) in each case, and wherein an expansion curve for determination of the TCL (T.i.) is normalized by definition such that a change in length is 0 ppm at 0° C.

13 . LAS glass ceramic according to claim 1 , which has a relative change in length (dl/l 0 ) of ≤|0.10| ppm within the temperature range from 20° C. to 30° C. and/or a relative change in length (dl/l 0 ) of ≤|0.17| ppm within the temperature range from 20° C. to 35° C., where “dl” denotes a change in length at a respective temperature and “10” is a length of a test specimen at 0° C., in each case on absolute values of the dl/l 0 values.

14 . LAS glass ceramic according to claim 1 , which has a relative change in length (dl/l 0 ) of ≤|0.30| ppm within the temperature range from 20° C. to 40° C., wherein “dl” denotes a change in length at a respective temperature and “10” is a length of a test specimen at 0° C., in each case on absolute values of the dl/l 0 values.

15 . LAS glass ceramic according to claim 1 , wherein a CTE-T curve within a temperature interval having a width of at least 30 K has a slope of ≤0±2.5 ppb/K 2 , wherein CTE-T curve is a graph of a function of a development of a Coefficient of Thermal Expansion (CTE) versus a Temperature T.

16 . LAS glass ceramic according to claim 1 , having thermal hysteresis of <0.1 ppm at least within the temperature range from 5° C. to 45° C.

17 . LAS glass ceramic according to claim 1 , containing As 2 O 3 in a content of 0.04 mol % of being essentially As 2 O 3 free.

18 . LAS glass ceramic according to claim 1 , containing, as refining agent, in place of As 2 O 3 or in addition to not more than 0.05 mol % of As 2 O 3 , at least one alternative redox refining agent and/or at least one evaporating refining agent and/or at least one decomposing refining agent.

19 . LAS glass ceramic according to claim 18 , wherein the alternative redox refining agent is at least one component selected from the group consisting of Sb 2 O 3 , SnO 2 , MnO 2 , CeO 2 , and Fe 2 O 3 and/or wherein the evaporating refining agent comprises a halogen with refining action and/or wherein the decomposing refining agent comprises a sulfate component.

20 . A precision component, for use in metrology, spectroscopy, measurement technology, lithography, astronomy or observation of the Earth from space comprising the LAS glass ceramic according to claim 1 .

21 . LAS glass ceramic according to claim 1 , wherein the content of fluorine is 0 to 0.5 mol %.

22 . LAS glass ceramic according to claim 1 , wherein the content of fluorine is 0 to 0.3 mol %.