Study On The Modification Of Co-Doping CaCu₃Ti₄O₁₂

Calcium Cupric titanate(CaCu₃Ti₄O₁₂,CCTO)is a kind of giant dielectric material with excellet properties,such as good pressure-sensitive characteristics,high frequency and temperature stability,etc.,and has a potential application prospect in the fields of memory,filter and electronic components technology.However,the high dielectric loss of CCTO limits its practical application.Therefore,while maintaining the high dielectric constant of CCTO material,reducing the dielectric loss and comprehensively improving the dielectric property of CCTO is one of the current research hotspots.Generally,single element doping just regulates the one of dielectric constant and the dielectric loss,and co-doping two or more elements can be usd to optimizing the dielectric constant and dielectric loss cooperatively,so as to improve the dielectric properties of CCTO.In this thesis,CCTO ceramic samples co-doped with cations(Sr²⁺,Co²⁺),donors and acceptors(Fe³⁺,Nb⁵⁺)and rare earth elements(Sm³⁺,La³⁺)were prepared separately by solid state reaction method.Three different co-doped systems were specifically studied on the influence of different doping elements and different doping concentration on the crystal structure and dielectric properties of CCTO materials by means of X-ray diffractometer,scanning electron microscope,LCR meter,electrochemical impedance meter and other test instruments.The main research contents and conclusions involved in this thesis are as follows:（1）Cation Sr²⁺and Co²⁺co-doped CCTO ceramic materials:sintered at 1100℃,the ceramic samples have no impurities and high density.The grain size is small,and thus increases the grain boundary density,increases the grain boundary resistance,and reduces the dielectric loss.The maximum dielectric constant of Ca_1-xSr_xCu_3-yCo_yTi₄O₁₂ceramic material can reach 4.4×10⁵in the frequency range of 20 Hz～300 k Hz,the minimum dielectric loss is 0.219;Besides,when the doping concentration is x=0.05,y=0.15,x=0.05,y=0.2,the dielectric loss of the ceramics almost does not change,showing good frequency stability.（2）Donor and acceptor Fe³⁺,Nb⁵⁺co-doped CCTO ceramic materials:CaCu₃Ti_4-x(Fe_1/2Nb_1/2)_xO₁₂ceramic materials sintered at 1100℃is pure,and the grain boundary resistance becomes larger than pure CCTO due to the reduction of grain size,and reduces dielectric loss simultaneously.The dielectric constant decreases slightly in the frequency range of 20 Hz～300 k Hz and the temperature range of 30℃～150℃,but still remains above 10⁴.The results show that the dielectric loss of co-doping CCTO decreases significantly,and meanwhile the frequency stability and temperature stability of the dielectric loss are good.（3）Rare earth elements Sm³⁺and La³⁺co-doped CCTO ceramic materials:Ca_1-xSm_xCu_3-yLa_yTi₄O₁₂ceramic materials sintered at 1100℃have no impurities generated.The dielectric loss of ceramic samples decreases significantly in the frequency range of 20 Hz～300 k Hz,and the dielectric loss has hardly any changes.It exhibits that co-doping CCTO has excellent frequency stability.In Ca_0.95Sm_0.05Cu_0.85La_0.15Ti₄O₁₂and Ca_0.95Sm_0.05Cu_0.8La_0.2Ti₄O₁₂ceramic samples,the dielectric loss has little change in the temperature range of 30～150℃,which shows that co-doping CCTO has good temperature stability.