电磁性能可调控金属陶瓷Y2Ti2O7/Fe的制备与表征

Fabrication and characterization of Y2Ti2O7/Fe cermets with tunable electromagnetic properties

采用固相反应与真空烧结先后制备Y2Ti2O7粉末与Y2Ti2O7/Fe金属陶瓷。XRD分析表明,所得Y2Ti2O7粉末为纯相,Y2Ti2O7/Fe金属陶瓷化学性质稳定,金属相与陶瓷相之间无界面反应产物。在10 MHz^1 GHz频段进行测试,发现Y2Ti2O7/Fe金属陶瓷的逾渗阈值处于Fe含量20%~30%(体积分数)之间。当Fe含量低于逾渗阈值时,介电常数、交流导电和磁导率均随Fe含量的增加而增加。当Fe含量超过30%时,金属陶瓷电抗与交流电导率发生突变,在整个测试频段都呈现负介电常数。Fe含量为40%的样品的磁导率在整个测试频段内小于1,且随频率增加不断下降,应归因于逾渗导电网络导致的抗磁性。在频率大于1 GHz时可能出现负磁导率,即实现电磁性能的双负性。

Y2Ti2O7 powders and Y2Ti2O7/Fe cermets were fabricated by solid-state synthesis and vacuum sintering,respectively.XRD analysis suggests that the Y2Ti2O7 powders are single-phase,and the Y2Ti2O7/Fe cermets are chemically stable,with no interfacial reaction products between the ceramic phase and the metal phase.During the electromagnetic testing under the frequencies of 10 MHz?1 GHz,the percolation threshold of the Y2Ti2O7/Fe cermets is found within the iron content range of 20%?30%(volume fraction).Under the percolation threshold,the permittivity,AC conductivity,and permeability all increase with the iron content.When the iron content is beyond 30%,the reactance and the AC conductivity change greatly,leading to a negative permittivity within the entire frequency range.For the iron content at 40%,the cermet exhibits a low permeability of less than 1,which decreases consistently with the increasing frequency.This should be attributed to the percolation induced diamagnetism as the result of the formation of conducting networks inside the cermet.Negative permeability can be further expected at the frequencies beyond 1 GHz.