The Preparation And Characterization Of NPO Dielectric Ceramics With High Permittivity

In order to prepare NPO ceramics with high dielectric constant and excellent comprehensive performance,(Bi0.9La0.1)2Ti2O7-(Ca0.8Sr0.2)TiO3(BLT-CST),(Bi0.9La0.1)2 Ti2O7-(Na0.5La0.5)Ti03(BLT-NLT)and(Bi0.9La0.1)2Ti2O7-(Ca0.6La0.8/3)TiO3(BLT-CLT)three kinds of system dielectric materials,using the oxide solid-phase reaction method to prepare the corresponding ceramic samples of the four system dielectric materials,studied the influence of different compositions on their dielectric properties,and Discuss the reason of its dielectric properties from the phase composition and micro-morphology.Finally,a 0.5BLT-0.5CLT ceramic with excellent comprehensive dielectric properties was successfully prepared.Its dielectric constant ?r?130,dielectric loss tan??0.0015,and temperature coefficient ?c?-6.7 ppm/?.The main contents of this article are as follows:Through phase analysis of xBLT-(1-x)CST(0.5<x<0.9)ceramics,within the composition range studied,the ceramics consist of two phases,one of which has a pyrochlore structure that deviates from the normal stoichiometric ratio of Bi1.74Ti2O6.624,the other phase is n(Ca0.8Sr0.2)TiO3·(Bi0.9La0.1)4Ti3O12 with bismuth layer structure,with the increase of x value,n gradually decreases,from n=2,sequentially reduced to n=1,n=0.5,when x=0.9,n<0.5,(Ca0.8Sr0.2)TiO3 solid solution into the(Bi0.9La0.1)4Ti3O12 layered structure.The dielectric properties of xBLT-(1-x)CST ceramics are closely related to the phase composition.Through phase analysis of xBLT-(1-x)NLT(0.4<x<0.75)ceramics,the pyrochlore phase Bi1.74Ti2O6.624 deviating from the stoichiometric ratio was detected in the ceramics within the range of the composition studied.In the range of 0.4?x?0.65,there is perovskite phase(Na0.5La0.5)TiO3.When x continues to increase to 0.75,the perovskite phase disappears.Within the composition range studied,the ceramics are also in the bismuth layered structure phase(Na0.5La0.5)TiO3?(Bi0.9La0.1)4Ti3O12,the high dielectric constant of xBLT-(1-x)NLT ceramics is very high may be related to the existence of this phase.Through phase analysis of xBLT-(1-x)CLT(0.3?x?0.7)ceramics,the pyrochlore phase Bi1.74Ti2O6.624 deviating from the stoichiometric ratio was detected in the ceramics within the range of the composition studied.In the range of 0.3<x<0.4,there is perovskite phase(Ca0.6La0.8/3)TiO3.When x continues to increase to 0.5,the perovskite phase disappears.In xBLT-(1-x)CLT ceramics,there is also a layered phase of bismuth n(Ca0.6Lar0.8/3)TiO3·(Bi0.9La0.1)4Ti3O12,within the composition range of 0.3?x?0.6,n=1,when x increases to 0.7,n=0.5.When x=0.5,the ceramic dielectric material satisfies the NPO characteristic,its dielectric constant K?130,dielectric loss tan??0.0015,and dielectric constant temperature coefficient TCK?-6.7ppm/?.