Preparation Of Sodium Potassium Niobate Based Piezoelectric Crystal And Study On Ceramic Doping Modification

In order to improve the properties of potassium sodium niobate based piezoelectric ceramics,the preparation of KNN piezoelectric Single crystal and the doping modification of ceramic are studied.Single crystal growth can be carried out by using a seedless single crystal solid phase method,that is,by mixing a small amount of Bi⁵⁺and Li⁺to appropriately extend the sintering time.In this experiment,a single crystal of?1-x?K_0.45Na_0.55Bi_0.004Nb_0.996O₃-xLiTaO₃ system was prepared.The prepared size is up to4mm*3mm*1.5mm,and it is found that the incorporated Bi⁵⁺,Li⁺and Ta⁵⁺can be completely incorporated to form a stable perovskite structure,in the orthogonal phase at room temperature,the microscopic surface of each single crystal has a typical single crystal morphology,where the PPT interval is closest to room temperature when x=0.04,the electrical properties at this time are preferably d₃₃=178pC/N,T_o-t=62?,T_c=411?,P_r=20.7?C/cm² and E_c=9.3kV/cm.At the same time,the influence of sintering time on the LT content of 0.04 was also found.It was found that the sinterability was best when the sintering time was around 12h,and the electrical properties at this time were also in the optimal range.The rare earth ions Ho³⁺and Tm³⁺were doped into KNN-LN ceramics by conventional high temperature solid phase method to form 0.94K_0.45Na_0.55NbO₃-0.06LiNbO₃:xHo/Tm system.It was found that the added Ho³⁺and Tm³⁺can be incorporated into the ceramic to form a perovskite structure.The original tetragonal phase is converted into an orthogonal phase,and the A-site ion in the structure is replaced first and then the B-site ion is replaced.It is found in the SEM image that the grain size can be greatly refined.The appearance of two dielectric peaks in the dielectric temperature spectrum indicates that the phase transition temperature To-t of the ceramic and the Curie temperature T_c are increased as the increase of x,and the doping amount is around 0.005 and the sintering temperature is 1070?.The phase transition temperature is close to room temperature,the electrical properties at this time were the best,respectively d₃₃=151 pC/N,T_o-t=49?,T_c=445?,P_r=13.0?C/cm²and E_c=9.8kV/cm.