Dielectric Temperature Characteristics of High-k (Ba, La)(Ti, Ce)O₃ Ceramics

Abstract

The dielectric temperature characteristics of the high-k (Ba_1-xLa_x)(Ti_1-x/4-0.05Ce_0.05)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 ΔT_mf′, Δε_mf′/ε_m′, 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 (ε_m′>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).