Crystal Structure and Microwave Dielectric Properties of CaTiO3–(Li1/2Nd1/2) TiO3–(Ln1/3Nd1/3)TiO3 (Ln=La, Dy) Ceramics

Abstract

Crystal structure and microwave dielectric properties of a xCaTiO₃–y(Li_1/2Nd_1/2)TiO₃–z(Ln_1/3Nd_1/3)TiO₃ (Ln=La, Dy) ternary system were studied. Crystal structures were refined by the Rietveld method using X-ray and neutron diffraction data. (Li_1/2Nd_1/2)TiO₃ and 0.2CaTiO₃–0.8(La_1/3Nd_1/3)TiO₃ ceramics showed the most reliable R-values with a tetragonal structure with a space group P-4b2 and lattice constants of a=b≈5.4 Å, and c≈7.6 Å. The A-site cations were ordered along the c-axis. When x≥0.3, the crystal structure changed to an orthorhombic CaTiO₃ type. The xCaTiO₃–y(Li_1/2Nd_1/2)TiO₃–z(La_1/3Nd_1/3)TiO₃ system showed microwave dielectric properties of ε _r=133, Q·f=1,450 GHz and τ_f=-17 ppm/°C at a composition of x=0.2, y=0.68, z=0.12. In xCaTiO₃–y(Li_1/2Nd_1/2)TiO₃–z(Dy_1/3Nd_1/3)TiO₃, dielectric properties of ε _r=97.6, Q·f=5,150 GHz and τ_f=+0.4 ppm/°C were obtained at x=0.30, y=0.40, z=0.30. The effect of each ternary system component on the dielectric properties is discussed.