Authors: Hua Jun Sun, Wen Chen, Qing Xu, Jing Zhou, Xiao Fang Liu
Abstract: Using Zr(NO3)4.5H2O as Zr source, PZT powder with a single-phase perovskite structure was synthesized by a sol-autocombustion method at a calcining temperature of 700°C. Compared with a solid-state reaction method, the calcining temperature of PZT can be lowered by 200°C when using the sol-autocombustion method. PMZN ceramic was prepared at a sintering temperature of
1050°C with the resulting PZT powder as a base, which can lower the sintering temperature by 150°C. The microstructure of the PMZN ceramic was investigated by XRD and SEM, and the dielectric and piezoelectric properties were measured. The results showed that the PMZN piezoelectric ceramic has a tetragonal perovskite structure, showing the main electrical properties as follows: Kp = 0.54, Qm = 1073, tgd £ 0.001, e33 T/ e0 = 1236, d33 = 454pC/N, and fs =136.1KHz.
219
Authors: Zhi Jun Xu, Rui Qing Chu, S.C. Cui, Jin Son Zhang
Abstract: Mixed-conducting ceramic oxide SrFeCo0.5Oy powders were prepared by a citrate method, and
the contributing factors to the formation of homogeneous fine powder with a pure perovskite-type
structure were ascertained. The resulting powder is pure, homogeneous and possesses a reasonably fine
particle size. Attempts were made to understand the synthesis process and it was confirmed that the
method produces powder had greater composition uniformity, lower residual carbonate levels and smaller
particle sizes.
971
Authors: Yong Zheng, Wen Lei, Hai Jian Bu, Xing Zhong Zhao
Abstract: Effects of calcining and sintering temperatures on the microstructure and the microwave
dielectric properties of Ba6-3x(Sm0.2Nd0.8)8+2xTi18O54(x=2/3) ceramics were studied. When the calcining
temperature was lower (1373K), the dielectric constant ε and the Qf factor initially increased with
increasing sintering temperature, but decreased when sintering temperature was higher than 1603K. As a
whole, the temperature coefficients of the resonant frequency τf tended to increase with increasing
sintering temperature. The microstructure of the sintered ceramic consisted mainly of columnar and
block-shape grains. The grain size increased with increasing sintering temperature. When the calcining
temperature was higher (1473K), εr and τf were nearly independent of sintering temperature. The
excellent microwave dielectric properties were achieved in the Ba6-3x(Sm0.2Nd0.8)8+2xTi18O54 (x=2/3)
ceramic calcined at 1373K and sintered at 1603K for 3 h: ε = 80.8, Qf = 8114 (GHz) and τf = 5.6.
258
Authors: Zhi Bin Tian, Xiao Hui Wang, Ji Li, Wei Zhao, Long Tu Li
Abstract: A citrate method to synthesize 0.94Bi0.5Na0.5TiO3-0.06BaTiO3 nano-powder was studied. The
stable gel was obtained by the control of the pH value and temperature of the precursor solution. The
BNBT nano-powder was produced after calcining the xerogel at 600°C~800°C. The average grain size of
the powder calcined at 700°C for 3 h is 50 nm, and the grain size of the ceramic sintered at 1080°C is 0.7
μm. The sintering temperature used is 100°C lower than the BNBT ceramic prepared by traditional
method, but the electrical properties were comparable. In addition, it was found that the ball-milling
process has important effect on the morphology of the ceramics and the orientation crystals were
eliminated due to the disintegration of agglomerates during milling.
103
Authors: Yi Hang Fang, Kai Miao, Si Qiao Feng, Jia Meng Cao, Huan Ping Wang, Shi Qing Xu
Abstract: The 0.95MgTiO3-0.05CaTiO3 (95MCT) powders and ceramics were prepared by a sol-gel method by using Mg(NO3)2•6H2O, Ca(NO3)2•4H2O and Ti(C4H9O)4 as the starting materials. The effects of calcination temperature on phase formation, morphology and particle size distribution of the proposed powders were examined, and the microwave dielectric properties of 95MCT ceramics made from different size particles were investigated. The dried gels were calcined at 600 °C, 700 °C, 800 °C and 900 °C, and the derived particle sizes of powders were 10-20 nm, 50-100 nm, 60-120 nm and 120-150 nm, respectively. The proper sizes, which range from 50-150 nm, lowered the sintering temperature of 95MCT ceramics effectively from 1400 °C to 1175 °C due to the high surface energy. Sintered at 1175 °C, the 95MCT ceramic prepared from 50-100 nm size particles had compact structure and exhibited good microwave dielectric properties: εr = 21.33 and Q×f = 36,315 GHz.
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