0.75CaTi(1-x)( Zn1/3Nb2/3) O-x(3)-0.25SmAlO(3) ( CT(1-x)ZN(x)SA) ( 0 <= x <= 0.09) ceramics were synthesized by a solid-state reaction process. The effects of ( Zn1/3Nb2/3)(4)+ co- substitution on the structure and dielectric properties of the ceramics were investigated. Every sample presented a single orthogonal perovskite structure. Moderate amounts of ( Zn1/3Nb2/3)(4+) substitution effectively improved the densification, dielectric properties, flexural strength, and lowered the sintering temperature, while excessive substitution deteriorated the overall performance. Excellent properties were achieved for 0.75CaTi(0.97)(Zn1/3Nb2/3)(0.03)O-3-0.25SmAlO(3) ceramics sintered at 1450 degrees C for 5 h, including epsilon(r) = 54.23, Q x f = 31,063 GHz (at 4.85 GHz), iota(f) = + 16.7 ppm/degrees C, a = + 10.99 ppm/degrees C, R = 135.16 MPa.