US 11,905,219 B2
Alumina ceramic
Yuji Fukasawa, Hadano (JP)
Assigned to COORSTEK KK, Tokyo (JP)
Filed by CoorsTek KK, Tokyo (JP)
Filed on Aug. 5, 2021, as Appl. No. 17/394,459.
Claims priority of application No. 2020-162410 (JP), filed on Sep. 28, 2020.
Prior Publication US 2022/0098111 A1, Mar. 31, 2022
Int. Cl. C04B 35/117 (2006.01); C04B 35/10 (2006.01)
CPC C04B 35/10 (2013.01) [C04B 35/117 (2013.01); C04B 2235/3205 (2013.01); C04B 2235/77 (2013.01)] 5 Claims
OG exemplary drawing
 
1. An alumina ceramic comprising alumina as a main component, an alkaline earth metal, and an element belonging to period 3, 4 or 5,
wherein the alkaline earth metal and the element belonging to period 3, 4 or 5 have a higher first ionization energy than aluminum,
wherein the alkaline earth metal is magnesium or calcium,
wherein the element belonging to period 3, 4 or 5 is scandium, titanium, yttrium or niobium,
wherein the alkaline earth metal, and the element belonging to period 3, 4 or 5 are a combination of Mg—Sc, Mg—Ti, Mg—Y, Ca—Sc, Ca—Y or Ca—Zr,
wherein an electronegativity difference between the alkaline earth metal and the element belonging to period 3, 4 or 5 is 0 or more and 0.6 or less,
wherein the total content of the alkaline earth metals and the elements belonging to period 3, 4 or 5 in the alumina ceramic is 0.05 wt % or more and 1 wt % or less based on the content of the alumina,
wherein a ratio (x/y) of the grain boundary area (x) to the grain area (y) in the alumina ceramic is 0.0001 to 0.0005,
wherein the density of the alumina ceramic is 3.8 g/cm3 or more and 4.0 g/cm3 or less, and
wherein the secondary electron emission coefficient of the alumina ceramic is 5.0 or less.