Ceramic with improved high temperature electrical properties for use as a spark plug insulator

1. A ceramic, comprising:

alumina in an amount between about 90 and about 99% by weight;

a zirconium containing compound in an amount between about 0.01% and about 1% by weight; and

an oxide mixture in an amount between about 1 and about 10% by weight before firing, said oxide mixture comprising:

a glass former;

a network modifier; and

alumina in an amount between about 16% and about 40% by weight after firing;

wherein the molar ratio of said glass former to said network modifier ranges between about 0.8:1 and 1.2:1.

2. The ceramic of claim 1 , comprising:

said alumina in an amount between about 94 and about 97% by weight;

said zirconium containing compound in an amount between about 0.1 and about 0.5% by weight; and

said oxide mixture in an amount between about 2.5 and about 5.9% by weight, wherein the molar ratio of said glass former to said network modifier equals between about 0.9 to 1 and 1.1 to 1.

3. The ceramic of claim 2 , comprising:

said alumina in an amount between about 95 and about 96.5% by weight;

said zirconium containing compound in an amount between about 0.25 and about 0.35% by weight; and

said oxide mixture in an amount between about 3.15 and about 4.75% by weight, wherein said network modifier comprises at least one of MgO, CaO, SrO, BaO, Na 2 O, K 2 O and Li 2 O.

4. The ceramic of claim 3 , wherein said network modifier comprises:

CaO in an amount between about 0.7 and 0.9 by mole fraction; and

MgO in an amount between about 0.1 and 0.3 by mole fraction.

5. The ceramic of claim 4 , wherein said network modifier comprises:

said CaO in an amount about 0.8 by mole fraction; and

said MgO in an amount about 0.2 by mole fraction.

6. The ceramic of claim 3 , wherein:

said network modifier comprises:

CaO in an amount between about 1.38 and about 1.95% by weight; and

MgO in an amount between about 0.15 and about 0.43% by weight; and

said glass former comprises SiO 2 in an amount between about 1.87 to about 2.28% by weight.

7. The ceramic of claim 6 , comprising:

said alumina in an amount about 95.67% by weight;

said zirconium containing compound in an amount about 0.3 1% by weight; and

said oxide mixture in an amount about 3.94% by weight.

8. The ceramic of claim 7 , wherein said oxide mixture comprises:

said CaO in an amount about 1.55% by weight;

said MgO in an amount about 0.27% by weight; and

said SiO 2 in an amount about 2.12% by weight.

9. The ceramic of claim 8 , further comprising:

at least one of Fe 2 O 3 , TiO 2 , P 2 O 5 , and K 2 O in a collective amount of about between 0.07% and 0.30% by weight.

10. The ceramic of claim 9 , comprising:

Fe 2 O 3 in an amount of up to about between 0.04% and 0.20% by weight;

TiO 2 in an amount of up to about between 0.0 1% and 0.05% by weight;

P 2 O 5 in an amount of up to about 0.0 1% by weight; and

K 2 O in an amount of up to about between 0.01% and 0.04% by weight.

11. The ceramic of claim 3 , comprising:

said alumina in an amount of about 95.55% by weight;

said zirconium containing compound comprising zirconia in an amount of about 0.31% by weight;

CaO in an amount of about 2.04% by weight; and

SiO 2 in an amount of about 2.02% by weight.

12. The ceramic of claim 11 , further comprising:

K 2 O in an amount of up to about 0.0 1% by weight;

TiO 2 in an amount of up to about 0.02% by weight;

P 2 O 5 in an amount of up to about 0.0 1% by weight; and

Fe 2 O 3 in an amount of up to about 0.03% by weight.

13. The ceramic of claim 1 , wherein:

said network modifier comprises at least one of MgO, CaO, SrO, and BaO;

said glass former comprises SiO 2 ; and

said oxide mixture is described by the following molar equation

(Mg v Ca w Sr x Ba y )O ZSiO 2,

wherein

V+W+X+Y =1,

and

0.8≦Z≦1.2.

14. The ceramic of claim 1 , wherein

said oxide mixture comprises a calcium alumino-silicate glass; and

said zirconium containing compound is ZrO 2 in an amount of between about 0.05 to 0.5%.

15. The ceramic of claim 14 , wherein said calcium alumino-silicate glass comprises:

alumina in an amount of up to about 40% by weight;

MgO in an amount of up to about 10% by weight; and

a balance of CaO and SiO 2 in an amount between about 50 to about 99% by weight.

16. The ceramic of claim 15 , wherein said SiO 2 comprises between about 40 to about 60% by weight of said balance of CaO and SiO 2 .

17. The ceramic of claim 3 , comprising:

said alumina in an amount of about 95.84% by weight;

CaO in an amount of about 2.05% by weight; and

SiO 2 in an amount of about 2.03% by weight.

18. The ceramic of claim 17 , further comprising:

K 2 O in an amount of up to about 0.0 1%;

TiO 2 in an amount of up to about 0.02%;

P 2 O 5 in an amount of up to about 0.01%; and

Fe 2 O 3 in an amount of up to about 0.03%.