Three zinc titanate compounds have been confirmed to exist in ZnO-TiO_2 system,namely,Zn_2TiO_4 (cubic),ZnTiO_3 (hexagonal)and Zn_2Ti_3O_8 (cubic).Due to its relativelylow sintering temperature and excellent microwave dielectric properties,moreover,for thelow cost of its raw materials,ZnO-TiO_2 ceramics has been considered to be a promisingcandidate for low temperature co-fired ceramics (LTCC),and then more and moreinteresting has been paid in the investigation of its structure,sintering behavior andmicrowave dielectric properties in recent years.However,the sintering aids ever used inZnO-TiO_2 ceramics have some shortcomings,in addition,ZnTiO_3,which has high Qfvalue at microwave frequencies,has unsuccessfully been prepared by solid state methodso far.Thus,the main purposes of this dissertation were to investigate the correspondingquestions of the aforementioned two aspects.In this dissertation,some basic questions about microwave dielectric ceramics(MWDC)were summarized,as well as the low temperature sintered MWDC and itsnewest development.A comprehensive survey of the synthesis,phase composition,structure and microwave dielectric properties of ZnO-TiO_2 ceramics were also made.ZnO-TiO_2 ceramics doped separately with V_2O_5,MoO_3 and 0.25CuO-0.75MoO_3 (inmole)were prepared by traditional fixed oxides method (i.e.solid state method),thesintering,phase composition,microstructure and microwave dielectric properties of theceramics prepared were characterized or measured by means of XRD,SEM,EDS and anet analyzer.As a result,pure ZnO-TiO_2 ceramics sintered at 1150℃for 4 h could get arelative density value of 94%,and exhibited microwave dielectric properties as follows:∈_r=25.17,Qf=7577 GHz,τ_f=+61 pprn/℃;The addition of V_2O_5 could effectivelyenhance the densification of ZnO-TiO_2 ceramics at lower sintering temperatures.ZnO-TiO_2 ceramics doped with 2 wt% addition of V_2O_5 sintered at 900℃for 4 h couldreach a relative density value of 95.3%,however,the microwave dielectric properties were seriously degraded (ε_r=23.32,Qf=6528GHzMoO_3 was less effective than V_2O_5 in theenhancement of the densification of ZnO-TiO_2 ceramics,the addition of MoO_3,however,could improve the microwave dielectric properties of the ceramics matrix.With 4 wt%MoO_3 addition,the ZnO-TiO_2 ceramics sintered at 1050℃for 4 h could reach a relativedensity value of 91%,andε_r=25.65,Qf=9881GHz,τ_f=+4 pprn/℃;The addition of0.25CuO-0.75MoO_3 could improve both the densification and microwave dielectricproperties of ZnO-TiO_2 ceramics.With 4 wt% 0.25CuO-0.75MoO_3 addition,the ZnO-TiO_2ceramics sintered at 975℃for 4 h could get a relative density value of 94%,and exhibitbetter microwave dielectric properties:∈_r=28.60,Qf=12150 GHz,τ_f=+17.8 ppm/℃;Zinc metatitanate,ZnTiO_3,starts to decompose into zinc orthotitanate (Zn_2TiO_4)andrutile at a sintering temperature of around 900℃,thereby leading to a difficulty in thesolid state synthesis of pure ZnTiO_3.There always exist considerable amounts of Zn_2TiO_4and rutile in the zinc titanate powders prepared.In this dissertation,the preparationprocessing and technique were investigated to synthesize pure ZnTiO_3 powder or at least azinc titanate powder with a higher mass fraction of ZnTiO_3.In details,commercial rutileand ZnO powders were used as precursors to synthesize zinc titanate powder via loweringthe calcining temperature,prolonging the soaking time and a multi-step calcining.As aresult,a zinc titanate powder with a 95.71% mass fraction of ZnTiO_3 was obtained.Incomparison,the mass fraction of ZnTiO_3 was only 66.15 % in the zinc titanate powdersintered at 800℃for 4 h with the same precursors.Anatase TiO_2 powders with different grain size,were employed to synthesize zinctitanate powders in a mole ratio ofZnO:TiO_2=1:1.The experimental results demonstratedthat,the existence of ZnO could lower the onset temperature of anatase to rutile transition.Meanwhile,a grain size effect in ZnO-TiO_2 system was found out for the first time,i.e.thelarger the mean grain size of precursor anatase TiO_2 powder,the less the mass content ofZnTiO_3 in the zinc titanate powder prepared.Conversely,the smaller the mean grain sizeof precursor anatase TiO_2 powder,the higher the mass content of ZnTiO_3 in the zinc titanate powder prepared.The above grain size effect was explained in this dissertation,onthe basis of which,an inference was drawn as follows:if the mean grain size of aprecursor anatase TiO_2 powder was small enough,very likely,ZnTiO_3 would not occur inthe zinc titanate powder prepared.Three rutile and ZnO mixed powders with different particle sizes in the same moleratio of ZnO:TiO_2=1:1 (symbolize by M0,M1 and M2,respectively.The size of M0 isthe smallest,the one of M2 is the largest)were used as precursors to synthesize zinctitanate powders.As a result,in the three zinc titanate powders individually derived fromM0 sintered at 630℃for 30 h,M1 sintered at 645℃for 30 h and M2 sintered at 675℃for 30 h,no Zn_2TiO_4 was detected.However,in the three zinc titanate powdersindividually derived from M0 sintered at 640℃for 4 h,M1 sintered at 655℃for 4 h andM2 sintered at 685℃for 4 h,Zn_2TiO_4 was detected.This demonstrated that,at the samesynthesis temperature,the larger the particle size of the precursor mixed powder,thesmaller the possibility of the occurrence of Zn_2TiO_4 in the zinc titanate powder prepared.In other words,under the same reaction conditions,the larger the particle size of theprecursor mixed powder,the higher the temperature at which Zn_2TiO_4 starts to appear.There are structure similarity phenomena in ZnO-TiO_2 system,i.e.,the connectionmanner of TiO6 octahedra in the structure of ZnTiO_3 is similar with the one of rutile,andthe connection manner of TiO6 octahedra in the structure of Zn_2TiO_4 and Zn_2Ti_3O_8 issimilar with the one of anatase.Accordingly,a structure similarity effect theory was putforward that,the formation of Zn_2TiO_4 or Zn_2Ti_3O_8 is limited by the presence of anatasewhereas ZnTiO_3 is only formed in the presence of rutile.On the basis of the experimentalresults,the structure similarity phenomena and its mechanism were investigated,and somedisagreements between theory and experimental results were also interpreted.