Preparation And Properties Of Sr₂NaNb₅O₁₅ And SrBi₂Nb₂O₉ Lead-Free Piezoelectric Ceramics Materials

In this paper,sodium strontium niobate ceramic powders were prepared by the solid phase,sol-gel method,respectively.Strontium bismuth niobate ceramic powderswere prepared by a solid phase method and molten salts method.Sintering temperature of ceramic powders wasoptimization;using air and protective atmosphere as sintering atmosphere,sodium,strontium niobate ceramics and strontium,bismuth niobate ceramics were prepared.The influence of sintering atmosphere and sintering temperature on phase composition,microstructure properties,dielectric,piezoelectric,ferroelectric properties of the ceramic materials were investaged.The influences of manganese oxide and rare earth oxide co-doped on phase composition,microstructure properties,dielectric,piezoelectric,ferroelectric propertiesof the ceramic materialswere investaged.Sr₂NaNb₅O₁₅ powders,having tungsten bronze structure,were successfully prepared by solid phase method,a sol-gel method.With the increase of sintering temperature,density,relative permittivity,piezoelectric strain constant,the piezoelectric voltage constant,planar electromechanical coupling coefficient and residual polarization constant of Sr₂NaNb₅O₁₅ceramics first increase and then decrease.The dielectric loss of Sr₂NaNb₅O₁₅ ceramicsessentially unchanged.The mechanical quality factor and the coercive field strength of Sr₂NaNb₅O₁₅ceramics decrease and then increase slightly.When protective atmosphere was used in the sintering process,the volatile alkali metal sodium element was suppressed,thereby strengthening the dielectric properties,piezoelectric properties and ferroelectric properties of ceramics.SrBi₂Nb₂O₉ powders,having a bismuth layer structure,were successfully prepared by solid phase method,molten salt method.As sintering temperature increasing,the relative density of SrBi₂Nb₂O₉ ceramics first increases and then decreases.The relative permittivity,dielectric loss of SrBi₂Nb₂O₉ ceramics overall have a downward trend.The piezoelectric strain constant of SrBi₂Nb₂O₉ ceramics overall shows growth in the state.Remaining constant polarization,spontaneous polarization constant and coercive field of ceramics were reduced after the first state to grow up.Being prepared by solid phase method,when added 0.5mol%MnO₂+0.25 mol%Eu₂O₃,the ceramic materials obtained the most excellent dielectric properties;when added 0.5mol%MnO₂+0.25 mol%La₂O₃ and added0.5mol%MnO₂+0.125 mol%Tb₄O₇,the ceramic materials had the most excellent piezoelectric properties;when added 0.5mol%MnO₂+0.25mol%Nd₂O₃,the ceramic materials showed the most excellent ferroelectric properties.Using molten salts method,when added 0.5mol%MnO₂+0.25 mol%Sc₂O₃,the ceramic materials showed the most excellent dielectric properties;when added 0.5mol%MnO₂+0.25mol%Sc₂O₃ and added0.5mol%MnO₂+0.25 mol%Y₂O₃,the ceramic materials had the most excellent piezoelectric properties;when added 0.5mol%MnO₂+0.25 mol%La₂O₃,the ceramic materials obtained the most excellent ferroelectric properties.