| Electronic components develop towards the direction of minaturizaiton,high integrated and high quality.And the dielectric materials have been optimized design.The improvement and innovation of the material dielectric constant??r?,dielectric tangent and temperature coefficients of dielectric constant????is becoming the mail solution nowadays.In this letter,Bismuth-based pyrochlores,Bi2O3-ZnO-Nb2O5,dielectric ceramic was doped for better dielectric properties,the crystal structure,phase constitution,chemical bond characters and dielectric properties were investigated systematically.In the course of the study,not only enrich and develop the theory for the dielectric materials but also a variety of new temperature stable Bi-based pyrochlore ceramic materials with good dielectric properties were presented.They can satisfy the engineering application.The main research and conclusion are as follows:Firstly,cubic structure Bi1.5Zn1.0Nb1.5O7 was investigated by traditional solid-state method.Zn2+?0.90?,CN=8?cation in the A-site was replaced by Mn2+?0.96?,CN=8?cation which has a similar ionic radius and large polarizability.We stydy the variation of micro-chemical bond and crystal structure with the increase of doped bivalent ions and investigate the influence of microstructure and phase content.The(Bi1.5Mn0.5)(Zn0.5Nb1.5)O7 ceramics sintered at a low temperature of 950°C with high dielectric constant of?r=135.46,low dielectric loss tan?=2.4×10-3 and a small temperature coefficient of??=-16 ppm/°C were achieved,which satisfied the EIA specification NP0.Secondly,cubic structure Bi1.5Zn1.0Nb1.5O7 dielectric materials doping with 0.1mol ratio of different radius of bivalent ions(Sr2+?Ca2+?Mn2+)were investigated and(Bi1.5Zn0..4M0.1)(Zn0.5Nb1.5)O7?M=Sr?Ca?Mn?Zn?dielectric ceramics were preparated.The influence in the bond length,microscopic structure and phase content of the system were studied with the bivalent ions doping.Based on ctystal structure refinement,we calculate the microscopic parameters such as lattice parameters,explore the relationship between macro dielectric properties with them and analyze the main factor of dielectric properties of Bi1.5Zn1.0Nb1.5O7 system.Thirdly,NiO was doped in Bi2Zn2/3Nb4/3O7 together for an improvement in dielectric properties.Bi2(Zn1-xNix)2/3Nb4/3O7?0.0?x?0.5?dielectric ceramics were prepared by solid-state reaction sintering.The influence of the system components,dielectric properties,phase content and crystalline structure were analyzed systemically,when this sytem introduced Ni2+ions.With the rising dopement of the Ni2+ions,the monoclinic phase structure made the transition to cubic phase structure.The Bi2(Zn1-xNix)2/3Nb4/3O7 ceramic sintered at a low temperature of 950°C exhibited excellent dielectric properties,when x value was 0.35.They were?r=98.46,tan?=7.6×10-4,??=0.96 ppm/°C,which can satisfy the engineering applications.Finally,have the opposite temperature coefficient of dielectric constant cubic Bi1.5ZnNb1.5O7??-BZN?in combination with monoclinic Bi2Zn2/3Nb4/3O7??-BZN?.Based on the above research,when x value increased,its cubic phase content decreased.What is more,a dielectric ceramic material with good dielectric properties was got.When x=0.05,it exhitited?r=110,tan?=5.4×10-4,??=-21 ppm/°C. |
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