A novel (1−𝑥)Ba_0.7Bi_0.3Fe_0.9Sn_0.1O₃-𝑥BaCo$_{0.02}^{II}$ Co$_{0.04}^{III}$Bi_0.94O₃ (0.2 ≤ 𝑥 ≤ 0.9) negative temperature coefficient (NTC) thick film thermistors with high thermistor constant was prepared by screen printing. The values of room-temperature resistivity, thermistor constant and activation energy of the thick film thermistors, increasing with the addition of Ba_0.7Bi_0.3Fe_0.9Sn_0.1O₃, are in the range of 35.5 𝛺cm-1.34 M𝛺 cm, 2067–6139 K and 0.177-0.527 eV, respectively. This means that the electrical properties of the thick films are adjustable at a wide range, depending on the compositions. Impedance analysis shows that the magnitude of thick film bulk resistance is mainly attributed to the contribution of grain boundary.

The effects of LiF addition on sinterability, microstructure and microwave dielectric properties of 0.25Ca_0.8Sr_0.2TiO₃–0.75Li_0.5Nd_0.5TiO₃ ceramics were investigated. The LiF addition enhanced the sintering temperature of 0.25Ca_0.8Sr0.2TiO3–0.75Li0.5Nd0.5TiO3 ceramics from 1200 to 1300°C, because the LiF addition could compensate the evaporation of Li during the sintering process. It was found that the bulk density and dielectric constant (𝜀_r) gradually decreased, the quality factor (𝑄_f) greatly increased and the temperature coefficient of resonant frequency (𝜏_f) shifted to a near-zero value with the increase in LiF addition. Obviously, excess Li addition could efficiently improve the microwave dielectric properties. In addition, 0.25Ca_0.8Sr_0.2 TiO₃–0.75Li_0.5Nd_0.5TiO₃ + 4.0 wt% LiF ceramics sintered at 1350°C for 4 h exhibited good microwave dielectric properties of 𝜀_r ∼ 123.4, 𝑄_f ∼ 2209 GHz (at 2.43 GHz) and 𝜏_f ∼ 12.3 ppm °C^–1.