Byung Sam Chun

Microwave dielectric properties of (1−x)(Ca0.7Nd0.2)TiO3–x(Li0.5Nd0.5)TiO3 ceramics

Abstract Microwave dielectric properties of (1− x )(Ca 0.7 Nd 0.2 )TiO 3 – x (Li 0.5 Nd 0.5 )TiO 3 (0.3≤ x ≤0.8) ceramics were investigated as a function of (Li 0.5 Nd 0.5 )TiO 3 content. In the entire composition range, a single phase of perovskite was detected. With increasing of (Li 0.5 Nd 0.5 )TiO 3 content, Qf value decreased due to the abnormal grain growth. Dielectric constant ( K ) increased up to x =0.5, and then decreased, which was dependent on the bond valence. The temperature coefficients of the resonant frequency (TCF) of the specimens decreased with the increase of (Li 0.5 Nd 0.5 )TiO 3 content due to the decrease of tolerance factor ( t ) in perovskite structure.

Estimation of Microwave Dielectric Properties of [(Na1/2La1/2)1-x(Li1/2Nd1/2)x]TiO3 Ceramics by Bond Valence

Microwave dielectric properties of the [(Na1/2La1/2)1-x(Li1/2Nd1/2)x]TiO3 (0.0≤x≤0.2) ceramics related to the bond valence were investigated as a function of (Li1/2Nd1/2)2+ content. A single perovskite phase with the cubic structure was obtained through the entire composition range. With an increase of (Li1/2Nd1/2)2+ content, the dielectric constant (K) increased due to the decrease of the average bond strength between cation and oxygen ion estimated from oxygen bond valence (VO). However, Qf value decreased with an increase of (Li1/2Nd1/2)2+ content due to the changes of composition. Temperature coefficient of resonant frequency (TCF) could be controlled from 480 ppm/°C at x=0.0 to 7.5 ppm/°C at x=0.2 due to the increase of B-site bond valence in ABO3 perovskite structure.