ZnAl_(2)O_(4) and ZnAl_(2)O_(4)-based ceramics have attracted much attention from researchers due to their good microwave dielectric,thermal and mechanical properties.In this work,the influence of 5%(in mass)CuO-TiO_(...ZnAl_(2)O_(4) and ZnAl_(2)O_(4)-based ceramics have attracted much attention from researchers due to their good microwave dielectric,thermal and mechanical properties.In this work,the influence of 5%(in mass)CuO-TiO_(2)-Nb_(2)O_(5)(CTN)ternary composite oxide additives with different composition ratios on sintering behavior and properties of ZnAl_(2)O_(4) microwave dielectric ceramics was investigated.When the molar fraction ranges of Cu,Ti and Nb elements in 5%CTN additives are 0.625-0.875,0-0.250 and 0.125-0.625,respectively,sintering temperature of ZnAl_(2)O_(4) ceramics can be reduced from above 1400℃to below 1000℃.The sintering additives CN(Cu:Nb=1:1,molar ratio)and CTN(Cu:Ti:Nb=4:1:3,molar ratio)can reduce sintering temperature of ZnAl_(2)O_(4) ceramics to 975 and 1000℃,respectively,while maintaining good dielectric properties(dielectric constantε_(r)=11.36,quality factor Q׃=8245 GHz andε_(r)=9.52,Q׃=22249 GHz)and flexural strengths(200 and 161 MPa),which are expected to be applied in preparation of low temperature co-fired ceramic(LTCC)materials with copper electrodes.Low-temperature sintering of the ZnAl_(2)O_(4)+CTN system is characterized as activated sintering.Nanometer-level amorphous interfacial films containing Cu,Ti,and Nb elements are observed at the grain boundaries,which may provide fast diffusion pathways for mass transportation during the sintering process.Valence changes of Ti and Cu ions,along with changes of oxygen vacancies,are confirmed,which provides a potential mechanism for reduced sintering temperature of ZnAl_(2)O_(4) ceramics.In addition,a series of reactions occurring at the grain boundaries can activate these boundaries and further promote the sintering densification process.These results suggest a promising way to design a novel LTCC material with excellent properties based on the low temperature sintering of ceramics with the sintering aid of CuO-TiO_(2)-Nb_(2)O_(5) composite oxide.展开更多
Ceramic dielectric materials with high dielectric strength and mechanisms of their internal factors affecting dielectric strength are significantly valuable for industrial application,especially for selection of suita...Ceramic dielectric materials with high dielectric strength and mechanisms of their internal factors affecting dielectric strength are significantly valuable for industrial application,especially for selection of suitable dielectric materials for high-power microwave transmission devices and reliable power transmission.Pure magnesium oxide(MgO),a kind of ceramic dielectric material,possesses great application potential in high-power microwave transmission devices due to its high theoretical dielectric strength,low dielectric constant,and low dielectric loss properties,but its application is limited by high sintering temperature during preparation.This work presented the preparation of a new type of multiphase ceramics based on MgO,which was MgO-1%ZrO_(2)-1%CaCO_(3-x)%MnCO_(3)(MZCM_(x),x=0,0.25,0.50,1.00,1.50,in molar),and their phase structures,morphological features,and dielectric properties were investigated.It was found that inclusion of ZrO_(2) and CaCO_(3) effectively inhibited excessive growth of MgO grains by formation of second phase,while addition of MnCO_(3) promoted the grain boundary diffusion process during the sintering process and reduced activation energy for the grain growth,resulting in a lower ceramic sintering temperature.Excellent performance,including high dielectric strength(Eb=92.3 kV/mm)and quality factor(Q×f=216642 GHz),simultaneously accompanying low dielectric loss(<0.03%),low temperature coefficient of dielectric constant(20.3×10^(–6)℃^(–1),85℃)and resonance frequency(–12.54×10^(–6)℃^(–1)),was achieved in MZCM1.00 ceramics under a relatively low sintering temperature of 1350℃.This work offers an effective solution for selecting dielectric materials for high-power microwave transmission devices.展开更多
铅基压电陶瓷因其优异的压电性能,被广泛应用于压电器件。其中,压电驱动器要求压电陶瓷具有较高压电性能并且在电场下具有较高的电致应变和较小的应变滞后。本研究通过施主-受主共掺,得到高压电性能和低电场应变滞后的PZT陶瓷。采用传...铅基压电陶瓷因其优异的压电性能,被广泛应用于压电器件。其中,压电驱动器要求压电陶瓷具有较高压电性能并且在电场下具有较高的电致应变和较小的应变滞后。本研究通过施主-受主共掺,得到高压电性能和低电场应变滞后的PZT陶瓷。采用传统固相反应法制备了(1-x)(Pb_(0.95)Sr_(0.05))(Zr_(53)Ti_(47))O_(3)-x BiAlO_(3)+0.2%MnO_(2)陶瓷(掺杂量为质量百分数),并对其微观结构和压电性能进行了研究。结果表明:BiAlO_(3)掺杂量较少时,陶瓷中缺陷偶极子的“钉扎”效应使得陶瓷畴壁转动困难,陶瓷压电性能较弱,应变滞后也较小。随BiAlO_(3)掺杂量增加,缺陷偶极子“钉扎”效应减弱,陶瓷的压电性能和应变滞后随之提高。本实验得到的性能最优组分为x=1.75%,该组份陶瓷的压电系数d_(33)=504 p C/N,机电耦合系数k_(p)=0.71,机械品质因数Q_(m)=281,居里温度T_(C)=312℃,在10k V/cm电场下的应变滞后仅为15%,并且还具有较好的温度稳定性,是一种具有应用价值的压电驱动器用压电陶瓷材料。展开更多
基金National Natural Science Foundation of China (U24A2052)Shanghai Eastern Talent Plan。
文摘ZnAl_(2)O_(4) and ZnAl_(2)O_(4)-based ceramics have attracted much attention from researchers due to their good microwave dielectric,thermal and mechanical properties.In this work,the influence of 5%(in mass)CuO-TiO_(2)-Nb_(2)O_(5)(CTN)ternary composite oxide additives with different composition ratios on sintering behavior and properties of ZnAl_(2)O_(4) microwave dielectric ceramics was investigated.When the molar fraction ranges of Cu,Ti and Nb elements in 5%CTN additives are 0.625-0.875,0-0.250 and 0.125-0.625,respectively,sintering temperature of ZnAl_(2)O_(4) ceramics can be reduced from above 1400℃to below 1000℃.The sintering additives CN(Cu:Nb=1:1,molar ratio)and CTN(Cu:Ti:Nb=4:1:3,molar ratio)can reduce sintering temperature of ZnAl_(2)O_(4) ceramics to 975 and 1000℃,respectively,while maintaining good dielectric properties(dielectric constantε_(r)=11.36,quality factor Q׃=8245 GHz andε_(r)=9.52,Q׃=22249 GHz)and flexural strengths(200 and 161 MPa),which are expected to be applied in preparation of low temperature co-fired ceramic(LTCC)materials with copper electrodes.Low-temperature sintering of the ZnAl_(2)O_(4)+CTN system is characterized as activated sintering.Nanometer-level amorphous interfacial films containing Cu,Ti,and Nb elements are observed at the grain boundaries,which may provide fast diffusion pathways for mass transportation during the sintering process.Valence changes of Ti and Cu ions,along with changes of oxygen vacancies,are confirmed,which provides a potential mechanism for reduced sintering temperature of ZnAl_(2)O_(4) ceramics.In addition,a series of reactions occurring at the grain boundaries can activate these boundaries and further promote the sintering densification process.These results suggest a promising way to design a novel LTCC material with excellent properties based on the low temperature sintering of ceramics with the sintering aid of CuO-TiO_(2)-Nb_(2)O_(5) composite oxide.
基金Student Training Program for Innovation and Entrepreneurship of Hangzhou Institute for Advanced Study,UCAS(CXCY20230305)Chinese Academy of Sciences Key Project(ZDRW-CN-2021-3-1-18)。
文摘Ceramic dielectric materials with high dielectric strength and mechanisms of their internal factors affecting dielectric strength are significantly valuable for industrial application,especially for selection of suitable dielectric materials for high-power microwave transmission devices and reliable power transmission.Pure magnesium oxide(MgO),a kind of ceramic dielectric material,possesses great application potential in high-power microwave transmission devices due to its high theoretical dielectric strength,low dielectric constant,and low dielectric loss properties,but its application is limited by high sintering temperature during preparation.This work presented the preparation of a new type of multiphase ceramics based on MgO,which was MgO-1%ZrO_(2)-1%CaCO_(3-x)%MnCO_(3)(MZCM_(x),x=0,0.25,0.50,1.00,1.50,in molar),and their phase structures,morphological features,and dielectric properties were investigated.It was found that inclusion of ZrO_(2) and CaCO_(3) effectively inhibited excessive growth of MgO grains by formation of second phase,while addition of MnCO_(3) promoted the grain boundary diffusion process during the sintering process and reduced activation energy for the grain growth,resulting in a lower ceramic sintering temperature.Excellent performance,including high dielectric strength(Eb=92.3 kV/mm)and quality factor(Q×f=216642 GHz),simultaneously accompanying low dielectric loss(<0.03%),low temperature coefficient of dielectric constant(20.3×10^(–6)℃^(–1),85℃)and resonance frequency(–12.54×10^(–6)℃^(–1)),was achieved in MZCM1.00 ceramics under a relatively low sintering temperature of 1350℃.This work offers an effective solution for selecting dielectric materials for high-power microwave transmission devices.
基金National Natural Science Foundation of China(51302295,61371059)Natural Science Foundation of Shanghai(13ZR1445600)Visiting Scholar Foundation of Key Discipline Laboratory of New Micro/Nano Device and System Technology in Chongqing University(2014MS05)
基金National Natural Science Foundation of China(51572279)973 Program(2015CB654604,2015CB654605)International Science and Technology Cooperation Program of China(2015DFA51100)
基金National Natural Science Foundation of China(51831010)National Key R&D Program(2021YFA0716502,2021YFB3800604)。
文摘铅基压电陶瓷因其优异的压电性能,被广泛应用于压电器件。其中,压电驱动器要求压电陶瓷具有较高压电性能并且在电场下具有较高的电致应变和较小的应变滞后。本研究通过施主-受主共掺,得到高压电性能和低电场应变滞后的PZT陶瓷。采用传统固相反应法制备了(1-x)(Pb_(0.95)Sr_(0.05))(Zr_(53)Ti_(47))O_(3)-x BiAlO_(3)+0.2%MnO_(2)陶瓷(掺杂量为质量百分数),并对其微观结构和压电性能进行了研究。结果表明:BiAlO_(3)掺杂量较少时,陶瓷中缺陷偶极子的“钉扎”效应使得陶瓷畴壁转动困难,陶瓷压电性能较弱,应变滞后也较小。随BiAlO_(3)掺杂量增加,缺陷偶极子“钉扎”效应减弱,陶瓷的压电性能和应变滞后随之提高。本实验得到的性能最优组分为x=1.75%,该组份陶瓷的压电系数d_(33)=504 p C/N,机电耦合系数k_(p)=0.71,机械品质因数Q_(m)=281,居里温度T_(C)=312℃,在10k V/cm电场下的应变滞后仅为15%,并且还具有较好的温度稳定性,是一种具有应用价值的压电驱动器用压电陶瓷材料。
