Study On Formulation And Technology Of Potassium Sodium Niobate-based Lead-free Piezoelectric Ceramics For Filters

At present,lead-based piezoelectric ceramics are widely used in the market,but because of its high lead content,it not only pollutes the environment,but also harms the human body.Therefore,it is of great social significance to study lead-free piezoelectric ceramics.Among lead-free piezoelectric materials,K_xNa_?1-x?NbO₃?KNN?piezoelectric ceramics have excellent piezoelectric properties and high Curie temperature.Filters generally require appropriate electromechanical coupling coefficient and mechanical quality factor to enhance selectivity.In addition,higher electromechanical coupling coefficient kp and piezoelectric constant d₃₃ can diversify the filter.In this paper,0.94K_0.48Na_0.52NbO₃-0.06LiSbO₃?0.94KNN-0.06LS?was modified by adding new components and ion doping in tow ways.The specific content is as follows:?1?The?0.94-x?KNN-0.06LS-xBM ceramics were prepared by introducing the component Bi₂O₃ and MnO₂?BM?,based on 0.94KNN-0.06LS.The phase structure,morphology,piezoelectric and dielectric properties,relaxation behavior and ferroelectric properties were studied.The results show that all the samples doped with BM are electrically perovskite.When x=0.2%,the ceramics have the best electrical properties:d₃₃=240pC/N,k_p=52%,?_r=1723,tan?=0.016.The electrical properties of ceramics have been improved obviously,the dielectric relaxation behavior has been enhanced,Curie temperature is above 320?,and the stability is good.?2?The?0.94-x?KNN-0.06LS-xBF ceramics were prepared based on 0.94KNN-0.06LS and the component Bi₂O₃ and Fe₂O₃?BF?was introduced.The phase structure,micro-morphology,piezoelectric properties and dielectric properties of the piezoelectric ceramics were studied.Doping BF can promote grain growth and improve electrical properties.When x=0.3%,ceramics have the best electrical properties:d₃₃=285pC/N,k_p=54%,?_r=2185,tan?=0.019,Q_m=66,T_c=340°C,?=1.4732,E_c=17.76kV/cm,P_r=21.48?C/cm².The results show that the ceramics have potential as high temperature and low frequency filters.?3?The?0.94-x?KNN-0.06LS-xBFO ceramics were prepared based on 0.94 KNN-0.06LS.The phase structure,micro-morphology,piezoelectric properties and dielectric properties of piezoelectric ceramics were studied.In nanometer BiFeO₃?BFO?,when x=0.3%,ceramics have the best electrical properties:d₃₃=275 pC/N,k_p=53.3%,?_r=1689,tan?=1.9%,Q_m=44,T_c=317?,?=1.8006,E_c=12.9kV/cm,P_r=18.55?C/cm².In micron BiFeO₃?BFO?,when x=0.5%,ceramics have the best electrical properties:d₃₃=260 pC/N,k_p=53.1%,?_r=1537,tan?=1.76%,Q_m=37,T_c=335?,?=1.5955,E_c=15.61kV/cm,P_r=19.33?C/cm².?4?Based on the optimal formulation of 0.937KNN-0.06LS-0.003BF,the effects of Co₂O₃ doping on phase structure,morphology,piezoelectric and dielectric properties,relaxation behavior and ferroelectric properties were studied.The results show that ceramics have the best comprehensive electrical properties when x=0.4%,d₃₃=265pC/N,k_p=53%,?_r=1587,tan?=2.1%,Q_m=39,T_c=360?,?=1.4206,E_c=13.46kV/cm,P_r=19.89?C/cm².