Patent ID: 8192852

Claim:
An insulator comprising: a ceramic composition, wherein the ceramic composition comprises crystalline grains and wherein the crystalline grains are substantially oriented to extend in a first direction to provide improved insulating properties in a direction perpendicular to the first direction, wherein the ceramic composition comprises: about 25-60% SiO 2 ; 15-35% R 2 O 3 , wherein the R 2 O 3 is 3-15% B 2 O 3 and 5-25% Al 2 O 3 ; 4-25% MgO+0-7% Li 2 O, wherein the total of MgO+Li 2 O is between about 6-25%; 2-20% R 2 O, wherein the R 2 O is 0-15% Na 2 O, 0-15% K 2 O, 0-15% Rb 2 O; 0-15% Rb 2 O; 0-20% Cs 2 O; and 4-20% F, wherein the first direction is circumferential and the direction perpendicular to the first direction is radial.