Preparation And Mechanism Of TiO₂ Based Giant Dielectric Ceramics

Dielectric material is one of the indispensable materials for electronic components.Facing the development of electronic components towards miniaturization and high performance,higher requirements are put forward for the performance of dielectric materials.Therefore,the research and development of a dielectric material with excellent electrical properties has become the focus of many scholars.TiO₂ is a typical dielectric material,which has abundant sources,non-toxic,good chemical stability,good conductivity and high breakdown resistance electric field strength.It is expected to be used in capacitors,energy storage and other electronic components.The dielectric constant of pure TiO₂ is very low?120?.Some researchers have found that the dielectric properties of TiO₂ can be greatly improved by doping modification.Although many researchers have prepared co-doped TiO₂with excellent dielectric properties,the influence of preparation process and ion doping combination on its dielectric properties is not clear,and there is still controversy on its giant dielectric mechanism.Therefore,it is of great significance to systematically study the influence of sintering process and ion doping combination on the dielectric properties and mechanism of co-doped TiO₂.In this paper,?Gd+Ta?and?Yb+Ta?co-doped TiO₂ ceramics were prepared by traditional solid-phase sintering.The effects of sintering process and ion doping combination on their micro morphology,phase composition and dielectric properties were studied.The mechanism of the giant dielectric properties of co-doped TiO₂ ceramics was explored.1.In this paper,the influence of sintering process on the dielectric properties of co-doped TiO₂ ceramics was investigated.The?Gd+Ta?co-doped TiO₂ ceramics were prepared by traditional solid-phase sintering at different sintering temperatures?1350?,1400?,1450?,1500??for 10 hours.It was found that all co-doped TiO₂ceramics have high density when the sintering temperature is above 1400?.The sintering temperature is 1450?,and the sample has the best dielectric properties.The dielectric constant is as high as 3.8×10⁵ and the dielectric loss is as low as 0.18 at room temperature and 1kHz.In addition,it is found that the dielectric constant of Ta doped TiO₂ increases,but the dielectric loss increases;Gd doped TiO₂ has low dielectric loss,but the dielectric constant is not high;when?Gd+Ta?co-doped TiO₂,the ceramic sample has not only high dielectric constant,but also low dielectric loss.2.In order to explore the reason why the co-doped TiO₂ ceramics have great dielectric properties,we also systematically explored the influence of different doping amounts on the electrical properties of?Gd+Ta?co-doped TiO₂ ceramics.The(Gd_0.5Ta_0.5)_xTi_1-xO₂ ceramics?x=0,0.5%,5%,10%,15%?were successfully prepared by traditional solid-phase sintering at 1450?for 10 hours.It is found that the dielectric constant is 4.8×10⁵ and the dielectric loss is 0.14 at room temperature and 1 kHz.The dielectric stability test shows that the dielectric constant of?Gd+Ta?co-doped TiO₂ ceramics still has a high value with the change of temperature,but the dielectric loss changes greatly.It is found by XPS that there are a large number of oxygen vacancies in the material.These oxygen vacancies will capture electrons and be bound in the lattice,so there are some defect complexes in the material.3.In order to further improve the dielectric properties of co-doped TiO₂ ceramics,we also prepared(Yb_0.5Ta_0.5)_xTi_1-xO₂ ceramics?x=0,0.5%,5%,10%,15%?.The dielectric properties of(Yb_0.5Ta_0.5)_xTi_1-xO₂ ceramics were the best when x=5%.The dielectric constant of(Yb_0.5Ta_0.5)_xTi_1-xO₂ ceramics was as high as 5.1×10⁵ and the dielectric loss was as low as 0.037 at room temperature and 1 kHz.The results of dielectric temperature stability test show that the change trend is similar to that of?Gd+Ta?co-doped TiO₂ ceramics.For x=5%(Yb_0.5Ta_0.5)_xTi_1-xO₂ ceramics,the good electrical properties can be kept in the temperature range of-50¹00?.It was found that?Yb+Ta?co-doped TiO₂ ceramics had certain pressure sensitivity.XPS analysis shows that(Yb_0.5Ta_0.5)_xTi_1-xO₂ ceramics have excellent dielectric properties,which can be explained by the electron pinning defect dipole cluster?EPDD?.