2006 Volume 114 Issue 1331 Pages 612-619
The dielectric temperature characteristics of the high-k (Ba1-xLax)(Ti1-x/4-0.05Ce0.05)O3 ceramics (BLTC: where x=0.01 to 0.05) with diffuse phase transition (DPT) behavior at different frequencies were studied. The ‘relaxor’ behavior of BLTC with respect to temperature (at 1 kHz) and frequency was quantified by means of some parameters, FWHM, δ, γ, and ΔTmf′, Δεmf′/εm′, repectively. DPT behavior and thermal hysteresis effect were discussed. The results indicated that the co-doping with La and 5 at% Ce causes strong diffusion of ferroelectric phase transition of BaTiO3 and pronounced rising of the permittivity peak (εm′>10000 for 0.02≤x≤0.05) in a frequency range 1 to 100 kHz. The rate that the permittivity peak shifts towards low temperature decreases slightly with increasing frequency, from 30.7°C/at% La at 1 Hz to 29.5°C/at% La at 100 kHz. This rate is faster than any BaTiO3 dopant reported previously. The x=0.03 sample meets Y5V and Z5U specifications at 1 kHz when the thermal hysteresis effect is considered. The increase in La concent (x) can markedly suppress the dielectric loss (tan δ).