| With the rapid development of social industrial information,electronic devices are becoming closer to miniaturization and high performance.Finding dielectric materials with excellent performance is the key to achieve this goal.Dielectric materials commonly used in practical device applications require a combination of high dielectric constant,ultra-low dielectric loss,and good temperature/frequency stability.However,it is difficult for existing dielectric materials(ferroelectric perovskite or non-ferroelectric oxides)to have all the above advantages at the same timeResearchers have found that(In+Nb)co-doped rutile titanium dioxide ceramics have strong frequency/temperature stability,the dielectric constant higher than 104,and dielectric loss of ceramic samples is lower to 0.05.This excellent dielectric properties immediately led to a series of research activities on the dual doping of TiO2 and titanium-based ceramics.SnO2 is isostructural with TiO2 showing similar varistor behavior.It is reasonably expected that acceptor/donor co-doping in rutile SnO2 would result in superior dielectric properties.Indeed,a CP behavior similar to that in(In+Nb)co-doped rutile titanium dioxide has recently been reported in(Al+Nb)co-doped Tin oxide ceramics.The close resembling of dielectric properties between the two oxides prompts us to perform detailed studies on(In+Nb)co-doped rutile phase oxide ceramics.Based on this,the(In+Nb)co-doped SnO2(INSO),(In+Nb)co-doped TiO2(INTO)two rutile phase ceramic materials were studied,and their dielectric properties and humidity sensitivity were systematically investigated.The specific work is as follows(1)(In+Nb)co-doped SnO2 ceramics,(In0.5Nb0.5)xSn1-xO2(INSO)with x=0,0.0005,0.001,0.01,and 0.1,were prepared by sol-gel method.We studied the dielectric and humidity sensitivity of these ceramic samples in detail.Our results revealed that there exists a critical doping level of xc～0.001 separating the dielectric behavior and humidity sensitivity of INSO into two different regions:In region I of x ≤ xc,the main relaxing species are In’Sn-OHO· complex dipoles,which greatly increases the dielectric constant.The humidity sensitivity was found to decrease with increasing doping level and have positive effect on the dielectric properties of the samples.In region Ⅱ of x>x,,the main relaxing species are localized holes,which leads to the formation of polaron relaxation and gradually weakens the enhancement of the dielectric constant of the samples.The humidity sensitivity was found to increase with increasing doping level and have negative effect on the dielectric properties of the samples(2)(In+Nb)co-doped titanium dioxide ceramics,InxNb0.05Ti0.95-xO2(INTO,x=0.05,0.06,0.07,and 0.08)were prepared by sol-gel method.We have discussed in detail the effect of different In/Nb atomic ratios,different sintering atmospheres(air atmosphere,oxygen atmosphere,nitrogen atmosphere)and oxygen annealing on the dielectric properties of(In+Nb)co-doped titanium dioxide ceramic samples.Our recent research shows that the dielectric constant,humidity sensitivity,and temperature stability of ceramic samples increase significantly with the co-doped In/Nb atomic ratio.Compared with sintering in air atmosphere,sintering in oxygen atmosphere will cause the dielectric constant of the sample to decrease,but the trend of its dielectric behavior does not change much,while nitrogen sintering not only improves the dielectric constant of the sample,but also changes the sample’s dielectric behavior significantly.Oxygen annealing greatly reduces the dielectric constant of the sample and removes the polarization relaxation caused by electron hopping between Ti3+ and Ti4+ ions near 150 K. |
