Study On Dielectric Behavior Of TiO₂ Ceramics Doped With Ti Powder

Due to the huge demand for energy storage and the rapid development of microelectronic technology,the search for high dielectric constant dielectric materials for electronic and energy storage devices has attracted wide attention.Compared with electrochemical energy storage,capacitor has the advantages of high power density and low dielectric loss,but the energy storage density greatly limits the application of capacitor.Increasing the dielectric constant of dielectric materials is the most direct and effective method to obtain high capacity in practical applications.Rutile TiO₂is potential dielectric material.Its dielectric properties have good temperature and frequency stability,low dielectric loss and large breakdown strength,and the dielectric constant needs to be improved.A large number of studies have shown that the point defect has a great influence on the dielectric properties of the material.The rutile TiO₂has excellent structural stability and is suitable for defect control.In this paper,the preparation process and dielectric behavior of metal Ti powder doped TiO₂ceramics are studied.A series of TiO₂ceramics with large dielectric constant are prepared by adjusting the sintering time,sintering temperature and material composition,and the preparation process of Ti powder doped TiO₂ceramics is gradually optimized.Through structural characterization,the relationship between dielectric behavior and point defects is systematically studied,and the systematic law between the structure and properties of metal Ti powder doped TiO₂ceramics is established.Different concentrations of metal Ti powder（0%,1%,2%,3%）doped TiO₂ceramics are successfully prepared by solid state reaction method.The effects of doping concentration on the microstructure and dielectric properties of TiO₂ceramics are systematically studied.It is found that the sample doped with 2%doping has the highest dielectric constant（～110000）and low dielectric loss（～0.029）.All samples possess outstanding stability in the temperature range of 25°C-400°C and frequency range of 1k Hz-1MHz.Through the analysis of defect structure,the trace doping of metal Ti powder can reduce Ti⁴⁺to Ti³⁺,and high temperature sintering will produce oxygen vacancies.In the system,defect clusters with the core of³⁺-_<sup>¨-³⁺might be formed.The polarization of these defect clusters is the main reason for the large dielectric constant,which provides a strong binding effect on electrons.The electrons can only jump in the local region,significantly reducing the dielectric loss of the whole material system.On the basis of 2%doping concentration,TiO₂ceramics with different sintering time（3h,5h,8h,10h）are prepared by solid-state reaction method.The effect of sintering time on the microstructure and dielectric properties of TiO₂ceramics is systematically studied.It is found that the sample obtains the best dielectric constant（～112000）and dielectric loss（～0.028）when the sintering time was 8h.SEM and EDS results show that TiO_2-xparticles about 200nm are grown on the grain boundaries when the sintering time is less than 8h,and disappear when the sintering time reaches 8h.The appearance of these titanium oxides is closely related to the formation of defect clusters in the system,which affects the dielectric behavior of the system.On the basis of 2%doping concentration and sintering for 8h,TiO₂ceramics at different sintering temperatures（1300°C,1350°C,1400°C,1450°C）are prepared by solid-state reaction.It is found that the sample has the best dielectric constant（～11000）and dielectric loss（～0.028）when the sintering temperature is 1400°C.The structural analysis showed that the samples sinter at 1400°C contained more Ti³⁺ions and defect clusters,resulting in higher dielectric constant.When the sintering temperature reaches 1450°C,the grains grow abnormally,and the decomposition of defect clusters leads to large dielectric loss.