| Speeding development of semiconductor industry promotes the progress of new technology and new materials.The application of high dielectric materials may solve the problem of reducing the semiconductor device size.Thus these materials have been widespread concerned.It has been found that Nb and Fe doubly codoped BaTiO3(BaTi1-x(Fe0.5Nb0.5)xO3,marked as BTFN)has quite high dielectric constant and high dielectric loss,which is usually explained with the core-shell structure and the coexistence of Fe2+ and Fe3+.In order to explore the ways to reduce the dielectric loss of BFTN materials,three parts of researches were carried out in this thesis.1.Al2O3 coated BTFN samples were prepared by impregnation and precipitation method.The effect of the Al2O3 content on the dielectric properties,the crystal structure,the surface morphology and composition of the samples were investigated.The results showed that all the prepared samples were of cubic perovskite structure.Al2O3 coating restrained the grain growth and the enrichment of Ti on the surface,increased the dielectric constant in high temperature zone,and also increased the dielectric loss,caused mainly by polarization loss.2.BTFN samples were treated by burying the pellet sample in the AI(NO3)3 power and calcining.The effect of the calcining temperature(750-950℃)on the dielectric properties,the crystal structure,the surface morphology and composition of the samples were investigated.The results showed that the treating with Al(NO3)3 could significantly reduce the dielectric loss and improve the dielectric constant.3.BTFN samples were treated with H2O2 for different times.The effect of the treating time on the dielectric properties,the crystal structure,and the surface composition of the samples were investigated.The results showed that suitable treating with H2O2 could apparently reduce Fe2+ content on the surface of the pellet samples and therefore apparently reduce the dielectric loss,meanwhile,increase the dielectric constant. |
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