Study On Dielectric Properties Of Doped SnO₂ Based Ceramic Materials

Giant dielectric materials have attracted much attention in applications such as miniaturization and energy storage of electronic devices.Among them,the rutile-type semiconductor oxide materials with different valence elements show excellent dielectric properties of giant dielectric and low loss in a wide temperature range,which has become a research hotspot in recent years.In the idea of co-doping cations above+4 valence provide electrons to increase the dielectric constant,and below the+4 valence of cation trapping electrons to reduce dielectric loss.It is well known that the dielectric properties of doped semiconductors are closely related to the grain boundary conduction activation energy and grain conduction activation energy of the material,but the influence of the ratio of grain boundary to grain conduction activation energy on dielectric properties has not been clearly reported.In this thesis,the dielectric properties of non-equal-doped SnO₂ were studied and the following results were obtained:Firstly,SnO₂ polycrystalline ceramic samples doped with non-equal ratios of In and Nb were synthesized by conventional high temperature solid-state reaction.The fixed Nb content is 5%,the In content ranges from 0 to 7%,that is In_x Nb_0.05Sn_0.95-xO₂.XRD,SEM and EDS test results show the synthesized samples are all pure phases.Secondly,the dielectric properties of the In_x Nb_0.05Sn_0.95-xO₂ series of samples were studied.The dielectric properties at room temperature show that the SnO₂ co-doped with In and Nb exhibits a phenomenon of coexistence of giant dielectric constant and low loss,and it is found that the sample exhibits the most excellent dielectric loss when the In doping ratio is 2%.Combined with XPS analysis,it was found that the co-doped samples contained Sn²⁺,which could capture or bind the electrons introduced by Nb⁵⁺doping,so that the optimal dielectric properties existed when the content of In was lower than that of Nb.Furthermore,the grain conduction activation energy and the grain boundary conduction activation energy of the series of non-equal ratio samples increase with the increase of In content,and the ratio of the conductivity activation energy of the grain boundary to the activation energy of the grain conductivity is larger,and the sample shows better dielectric behavior,which will provide a new way of thinking for the exploration of new giant dielectric materials.Finally,the dielectric properties of In_0.02Nb_0.05Sn_0.93O₂ and different proportions of SrSnO₃ composites were investigated.Doping does not make SrSnO₃ have a large dielectric constant,but after combining In_0.02Nb_0.05Sn_0.93O₂ material with different proportions of SrSnO₃,the sample can maintain low dielectric loss and dielectric constant at a wide temperature.The interval has increased by 2 times.Further analysis of the electrical properties of the composites reveals that the ratio of the grain boundary conduction activation energy to the grain conduction activation energy of the composite material is large,the dielectric constant of the material is high and the loss is small,which again shows that the ratio of activation energy can be found more excellent giant dielectric materials provide positive prediction and guidance.