Low-temperature Sintering Giant Dielectric, Low-loss TiO₂-based Composite Ceramics

With the vigorous development of electronic components,especially in recent years,the trend is toward miniaturization and high integration.High dielectric constant has become an important parameter,so colossal permittivity materials have received more attention and their excellent dielectric properties play an important role in devices such as capacitors,filters,and resonators.Recently researchers found that(In+Nb)co-doped TiO₂ ceramics have quite excellent dielectric properties,with a dielectric constant of up to 10⁴ and a dielectric loss of less than 5%.The dielectric constant and dielectric loss have good temperature stability in the range of 80 K to 450 K,and good frequency stability in the range of 20 Hz to 2 × 10⁶ Hz.Liu!s research group analyzed the origin of colossal permittivity and proposed that defective dipole clusters are the main cause of colossal permittivity.Although the origin of co-doped TiO₂ colossal permittivity is currently in dispute,its work has opened up new research directions for the development of colossal permittivity materials,and also laid the foundation for the later doping modification and addition of second-phase modification.This paper took(In+Nb)co-doped TiO₂ ceramics as the research object,and improved the preparation process.First,the ceramic cylinder with a large volume and high dielectric constant is sintered by the traditional solid-state method,followed by grinding and high energy ball milling to obtain the nano colossal permittivity powder.which is used as a precursor powder to improve the ceramic performance by doping and introducing a second phase.Utilizing the colossal permittivity properties of nano colossal permittivity powder and the low-temperature sintering effect of nano-size,it is aimed to retain the excellent dielectric properties of the original(In+Nb)co-doped TiO₂ ceramics,reduce the sintering temperature,and increase the bias stability of the electrical performance,to satisfy the commercial development conditions.(1)The traditional solid-state method combined with high-energy ball milling was used to prepare colossal permittivity nano-powder.The colossal permittivity properties of the ceramics prepared by using the colossal permittivity nano powder as the precursor powder at different sintering temperatures and after annealing were studied.Compared with the dielectric properties of(In+Nb)co-doped TiO₂ ceramics under the same sintering condition,the colossal permittivity powder retains the colossal permittivity properties at a lower sintering temperature.Pure nano-TiO₂ was introduced into the colossal permittivity powder as the second phase,and the colossal permittivity low-loss ceramic was successfully sintered at 1250?,with a dielectric constant of about 33000 and a dielectric loss of about 0.02(@1kHz).(2)Introducing CaTiO.as the second phase,(1-x)(In_0.5Nb_0.5)_0.01Ti_0.99O₂+xwtCaTiO₃ composite ceramics were prepared,and the effects of second phase in the microstructure,dielectric properties,and bias voltage performance were studied.When x?0.3,the composite ceramic retained the colossal permittivity property,and the ceramic sintered at 1200? exhibited excellent comprehensive performance with colossal permittivity and low dielectric loss in 500 Hz?30 MHz,and possessed well frequency stability,while the bias performance has been greatly improved.The dielectric performance maintains bias stability within the external bias range of 0 V/cm?450 V/cm.(3)(1-x)(In_0.5Nb_0.5)_0.01Ti_0.99O₂+xwtLiF(0 ?x ? 0.09)ceramics were prepared by the traditional solid-state reaction method,and the effects of LiF addition in microstructure,dielectric properties,bias voltage performance were studied.The introduction of LiF greatly reduces the sintering temperature of(In+Nb)co-doped TiO₂ ceramics.The ceramics sintered at 100? possessed excellent comprehensive properties,with huge dielectric performance in a wide frequency range of 10 Hz to 250 MHz and dielectric loss of less than 0.1.The ceramic also exhibits excellent performance in terms of resistance to DC bias,and can maintain stable dielectric properties under an external bias of 0 V/cm?1000 V/cm.