Crystal Structure and Microwave Dielectric Properties of CaTiO₃–(Li_1/2Nd_1/2) TiO₃–(Ln_1/3Nd_1/3)TiO₃ (Ln=La, Dy) Ceramics

Abstract

Crystal structure and microwave dielectric properties of a x CaTiO 3 – y (Li 1/2 Nd 1/2 )TiO 3 – z (Ln 1/3 Nd 1/3 )TiO 3 (Ln=La, Dy) ternary system were studied. Crystal structures were refined by the Rietveld method using X-ray and neutron diffraction data. (Li 1/2 Nd 1/2 )TiO 3 and 0.2CaTiO 3 –0.8(La 1/3 Nd 1/3 )TiO 3 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 CaTiO 3 type. The x CaTiO 3 – y (Li 1/2 Nd 1/2 )TiO 3 – z (La 1/3 Nd 1/3 )TiO 3 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 x CaTiO 3 – y (Li 1/2 Nd 1/2 )TiO 3 – z (Dy 1/3 Nd 1/3 )TiO 3 , 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.