Patent ID: 7378050

Claim:
A method of producing a translucent ceramic having a refractive index of equal to or more than 1.9 and being paraelectric and comprising a polycrystalline oxide perovskite crystal phase, the method comprising the steps of: molding a ceramic material powder and a binder into a predetermined shape to thereby yield a translucent ceramic green compact comprising a perovskite crystal phase represented by the formula ABO 3 wherein A is an A-site element comprising Ba in the perovskite crystal phase; and B is a B-site element and is two of Mg, Ta, Nb, Zn and Ta in the perovskite crystal phase, bringing the ceramic green compact into contact with a ceramic powder having substantially the same composition with the ceramic material powder, and firing the ceramic green compact in contact with the ceramic powder to thereby yield said translucent ceramic, wherein the perovskite crystal phase is a member of the group consisting of (a) Formula I: Ba{(Sn u Zr 1-u ) x Mg y Ta z } v O w in which x+y+z=1, 0≦u≦1.00, 1.00≦v≦1.05; w is arbitrary; and x, y, and z lie within the range enclosed by Point A (x=0.40, y=0.23, z=0.37), Point B (x=0, y=0.39, z=0.61), Point C (x=0, y=0.27, z=0.73), and Point D (x=0.40, y=0.11, z=0.49), excluding the line between Point A and Point B, (b) Formula II: Ba(Zr x Zn y Ta z ) v O w in which x+y+z=1, 1.00≦v≦1.050; w is arbitrary; and x, y, and z in Formula I lie within the range enclosed by Point A (x=0.01, y=0.29, z=0.70), Point B (x=0.06, y=0.29, z=0.65), Point C (x=0.06, y=0.36, z=0.58), and Point D (x=0.01, y=0.36, z=0.63), and (c) Formula III: Ba{(Sn u Zr 1-u ) x (Zn t Mg 1-t ) y Nb z } v O w in which x+y+z=1, 0≦t≦1.00, 0≦u≦1.00, 1.00≦v≦1.450; w is arbitrary; and x, y, and z lie within the range enclosed by Point A (x=0.25, y=0.35, z=0.40), Point B (x=0, y=0.35, z=0.65), Point C (x=0, y=0.20, z=0.80), Point D (x=0.10, y=0.10, z=0.80), Point E (x=0.55, y=0.10, z=0.35), Point F (x=0.35, y=0.30, z=0.35), and Point G (x=0.30, y=0.30, z=0.40).