Jiaqi Li,Junjun Wang,Fengmin Wu,Hui Ma,Tianyi Ma,Yu Tian,Danqing Liu,Bin Yang
In this paper, Bi2O3-doped (K0.5Na0.5)NbO3(x = 0.1, 0.2, 0.3, 0.4) lead-free ceramics are prepared by a conventional solid-state reaction and analyzed by studying the structure, ferroelectric, and piezoelectric properties. It is found that the doping of Bi2O3increases the proportion of the trigonal phase in KNN ceramics, thus enabling the construction of KNN ceramics with an orthogonal–trigonal phase boundary at room temperature. At the same time, doping with Bi2O3can reduce the grain size and improve grain size uniformity of the ceramics. The KNN-0.1%Bi2O3ceramic has the best piezoelectric properties in all composition; the results are as follows:d33= 121pC/N,kp= 0.474,kt= 0.306.Keywords:KNN lead-free ceramics;Bi2O3doping;grain effects;piezoelectric property
NiCuZn ferrite is a material suitable for low-temperature co-fired ceramic (LTCC) technology due to its high permeability and relatively low sintering temperature . The main research questions regarding NiCuZn ferrites are focused on reducing the sintering temperature of the NiCuZn ferrites to achieve compatibility with the Ag electrodes and improve their electromagnetic properties. In this study, the electromagnetic properties of NiCuZn (Ni 0.29 Cu 0.14 Zn 0.60 Fe 1.94 O 3.94 ) ferrites were enhanced by doping with Bi 2 O 3 , resulting in a reduction of the sintering temperature to 925 °C. The findings show that a suitable concentration of Bi 2 O 3 doping could promote the growth of grains and result in NiCuZn ferrites with denser microstructures sintered at a low temperature. Furthermore, adding 0.30 wt% Bi 2 O 3 to NiCuZn ferrite enhances its electromagnetic properties, such as a high real part of permeability (∼937.6 @ 1 MHz), high saturation magnetization (∼60.353 emu/g), low coercivity (∼0.265 kA/m), and excellent dielectric constant (∼14.71 @ 1 MHz). In addition, the chemically compatible Ag electrodes suggest that the NiCuZn +0.30 wt% Bi 2 O 3 ceramics may be acceptable for LTCC technology.
FEI LI,JINGDE ZHANG,JUNPENG LUAN,YALEI LIU,JIANXUN HAN
The NiO/YSZ anode materials of SOFCs with Bi 2 O 3 as sintering aids were successfully prepared by dry-pressing process. The effects of Bi 2 O 3 content on the sintering properties of NiO/YSZ anode materials were studied, including the effects on the density, open porosity, weight loss, phase composition, microstructure, mechanical strength and electrical conductivity. In particular, the weight loss, relative density and bending strength of the sintered NiO/YSZ ceramics increased with the increase of Bi 2 O 3 content while the open porosity decreased gradually. The density of the NiO–YSZ ceramics with 6 wt.% Bi 2 O 3 sintered at 1250 ∘ C could reach that of the ceramics without Bi 2 O 3 sintered at 1400 ∘ C. For Bi 2 O 3 concentration higher than 6 wt.%, phase transformation of zirconia from monoclinic to cubic structure occurs, causing volume change and microcracks in the anode materials. Therefore, the optimum adding amount of Bi 2 O 3 is 6 wt.%, which can reduce the sintering temperature to 1250 ∘ C. The ceramics with 6 wt.% Bi 2 O 3 have relatively high bending strength and low sintering temperature. This is of great significance for improving the performance of the anode and cutting the cost.
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