Study On Doping Modification Of TiO₂-Based Giant Dielectric Constant Ceramics

Giant dielectric constant material refers to the material with dielectric constant above 10³.Compared with traditional giant dielectric constant ceramics,rutile TiO₂ ceramics have attracted much attention due to their high dielectric constant,low dielectric loss as well as good frequency and temperature stability.In this paper,Sm³⁺and Ta⁵⁺were selected to dope TiO₂.Sm single-doped TiO₂,Ta single-doped TiO₂ and Sm plus Ta co-doped TiO₂ systems were prepared by solid-state reaction sintering.The effects of doping element type and content on the structure and properties of TiO₂-based ceramics were systematically studied,and the physical origin of giant dielectric constant was explored.The specific research results are as follows:（1）The effects of doping element types(Sm single doped(Sm_0.04Ti_0.96O₂),Ta single doped(Ta_0.04Ti_0.96O₂)and Sm and Ta co-doped(Sm_0.5Ta_0.5)_0.04Ti_0.96O₂)on the structure and dielectric properties of TiO₂-based ceramics were investigated.Element doping increases the lattice parameters of the samples,which means that Sm³⁺and Ta⁵⁺are successfully doped into the TiO₂ lattice.There are a small amount of TiO_0.892 non-stoichiometric compounds second phase exists in the samples,and a small amount of Sm₂Ti₂O₇ second phase exists in Sm_0.04Ti_0.96O₂and(Sm_0.5Ta_0.5)_0.04Ti_0.96O₂ ceramics.Element doping can increase the density of TiO₂ ceramics and reduce its average grain size.The dielectric constants of(Sm_0.5Ta_0.5)_0.04Ti_0.96O₂ and Ta_0.04Ti_0.96O₂ ceramics are greatly improved,showing giant dielectric properties.At 1 k Hz,(Sm_0.5Ta_0.5)_0.04Ti_0.96O₂ ceramics have the best dielectric properties at room temperature:the dielectric constant is 1.6×10⁵ and meet the temperature coefficient requirements of the dielectric constant of X5R,X7R,Z5U and Y5V capacitors.（2）The effects of Ta doping content（1 wt.%,2 wt.%,3 wt.%,5 wt.%）on the structure and dielectric properties of TiO₂-based ceramics were investigated.The lattice parameters of the samples increase with the increase of Ta doping content,which indicates that the successful doping of Ta⁵⁺leads to lattice expansion of TiO₂.There is a small amount of TiO_0.892 non-proportional compound second phase exists in the sample.The average grain size of all samples increases with the increase of Ta doping content.The dielectric constant of the sample increases first and then decreases with the increase of the doping element content.At 1 k Hz,Ta_0.03Ti_0.97O₂ceramics have the best dielectric properties at room temperature:the dielectric constant is 2.8×10⁵,the dielectric loss is 0.27 and meet the temperature coefficient requirements of the dielectric constant of Z5U and Y5V capacitors.（3）The effects of Sm and Ta doping content（2 wt.%,3 wt.%,5 wt.%）on the structure and dielectric properties of TiO₂-based ceramics were investigated.The lattice parameters of the samples increase with the increase of Sm and Ta co-doping content,which represents the lattice expansionof TiO₂ caused by the successful doping of Sm³⁺and Ta⁵⁺.There are a small amount of TiO_0.892 non-stoichiometric compound and Sm₂Ti₂O₇ second phase in the samples.The grain size of ceramics increases with the increase of Sm and Ta doping content.The dielectric constant of the sample increases with the increase of the doping element content.At 1 k Hz,(Sm_0.5Ta_0.5)_0.05Ti_0.95O₂ ceramics have the best dielectric properties at room temperature:the dielectric constant is 1.5×10⁵,the dielectric loss is 0.043 and meet the temperature coefficient requirements of the dielectric constant of X5R,X7R,Z5U and Y5V capacitors.（4）The dielectric properties,AC impedance and XPS analysis of the ceramics confirmed that the source of the giant dielectric constant of TiO₂-based ceramics was the result of EPDD and IBLC effects.