Papers by Keyword: PMN

Abstract: Both PMN and PZT are perovskite oxides and typical functional materials applicable to various devices for its chemistry and physics properties. The conventional method solid-state reaction method has some drawbacks of high reaction temperature, large particle size and limited degree of chemical homogeneity. So, an easy, low cost and environmental method of synthesizing fine and homogenous powders is required. This paper discusses the synthesis of PMN and PZT by the new mechano-chemical method, the screw grinding method. Through experiments, it was found that the mechanism of mechano-chemical method and solid phase diffusion method were completely different, thus the pyrochlore phase was avoided, and the phase purity of powders was developed. And a higher power could greatly short the time of the mechano-chemical reaction time, improving the phase purity and the dispersion of the powder.

Abstract: To improve the temperature stability of PMN(Pb(Mg_1/3Nb_2/3)O₃)-based ceramics, PMN-based composite ceramics were prepared by co-sintering two kinds of ceramics with different curie temperature. One unit is MHT(0.82PMN (Pb (Mg_1/3Nb_2/3) O₃) -0.18PT (PbTiO₃) (the curie temperature Tm=74°C)), and the other unit is MLT (0.88PMN (Pb (Mg_1/3Nb_2/3) O₃)-0.12BT (BaTiO₃) (the curie temperature Tm=-50°C)). The effects of the sintering temperature and the ratio of high and low T_m units on dielectric temperature stability were studied. The results show that the temperature stability can be improved greatly by co-sintering and coating method. The results show that PMN(Pb(Mg_1/3Nb_2/3)O₃)-based composite ceramics are promising candidate for practical applications.

Abstract: The PANI/PMN composite was prepared by one-step in-situ polymerization method and was characterized via FT-IR, XRD, SEM and TG. The results indicate that the best reaction conditions of in-situ polymerization are 0°C/24h.The PMN powder are entirely coated with PANI, when composite contains more than 60% PANI by volume. The steric hindrance effect of PMN powder decreases the crystallization degree of PANI which polymerizes on the surface of PMN powder in the process of in-situ polymerization. The main weight loss occurring between 300 and 480°C corresponds to the degradation of the PANI polymer chain.

Abstract: A relaxor ferroelectric material, Pb(Mg1/3Nb2/3)O3 (PMN) powder with a pyrochlore-free phase, was prepared by using a one-step calcinations method. The pyrochlore phase was prevented by coating Mg(OH)2 on Nb2O5 particles. Pure-perovskite PMN powder was synthesized by a single calcination of the coating powder mixed with appropriate amounts of PbO at 900 oC for 2 h. The pyrochlore-free perovskite PMN powders were sintered to 96.9% density at 1100 oC. The sintered PMN ceramics exhibited a dielectric constant maximum of ~11 700 at room temperature at a frequency of 1 kHz.