Study On The Texture And Electrical Properties Of Ternary PSN-PMN-PT Ceramics

Piezoelectric material,as a kind of functional material,which can realize the mutual conversion between mechanical energy and electric energy has been widely used in various fields.The continuous improvement and enhancement of piezoelectric properties has always been a hot topic in this research field.Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃（PMN-PT）solid solution is favored by researchers because of its excellent piezoelectric properties,but its applications are limited by the low Curie temperature and coercivity field.In this thesis,to obtain the piezoelectric ceramics with high piezoelectric constant and Curie temperature simultaneously,the end member Pb(Sc_1/2Nb_1/2)O₃（PSN）with high Curie temperature was introduced into PMN-PT system.The effects of composition on crystalline structure,electrical properties and phase transformation behavior of ceramics were investigated in detail.On this basis,doping and texturing approaches were used to further promote the piezoelectric properties and the their influence on the phase structure,electrical properties and phase transformation behavior of ternary ceramics were studied in depth.The 0.15PSN-（0.85-x）PMN-xPT（x=0.31-0.40）ternary ceramics were prepared by traditional solid-state reaction method.The phase structure of ceramics was studied by XRD,it is found that with the increase of PT content,phase transition sequence of the ceramic is from M_C+R to M_C+M_A+R phases,and then to M_C+T.The phase transition temperature T_ff decreases with the increase of PT content and cannot be detected above room temperature when x=0.38,meanwhile,the Curie temperature T_c and coercive field E_c exhibit the gradually increased tendency.The corresponding d₃₃ increases firstly and then decreases as the PT content increases.The ceramic with x=0.37 shows high T_c,large E_c and high d₃₃(T_c=205℃,E_c=7.3 k V/cm,d₃₃=610 p C/N),simultaneously,which are obviously better than those of PMN-PT ceramics,indicating that it is feasible to introduce PSN into PMN-PT for improving the electric performance and Curie temperature.Besides,it can be concluded that the high piezoelectric constant is derived from the phase coexistence of M_C and T with appropriate proportion.For the temperature stability study of x=0.37 ceramics,when the annealing temperature is 140℃,the remained d₃₃ still maintains 92%of value before annealing.These results show that x=0.37ceramics have good comprehensive properties and temperature stability,which have a certain potential in practical applications.In this part,we selected 0.15PSN-0.52PMN-0.33PT ternary ceramic as the matrix and Sm³⁺as dopant.The Pb_1-1.5ySm_y[(Sc_1/2Nb_1/2)_0.15(Mg_1/3Nb_2/3)_0.52Ti_0.33]O₃（y Sm-PSN-PMN-0.33PT,y=0.005,0.01,0.015,0.02 mol）ceramics with different Sm³⁺contents were prepared by traditional solid-phase reaction method.The phase structure of the ceramics was studied by XRD,it is found that Sm³⁺substitution at A site is beneficial to the formation of the tetragonal phase.With the increase of Sm³⁺content,the T_ff and T_c show a monotonously decrease,and the d₃₃ increases firstly and then decreases.The optimized electric properties are achieved in 0.015Sm-0.15PSN-0.52PMN-0.33PT ceramics:T_c=141℃,d₃₃=860 p C/N,k_p=0.65,E_c=5.83 k V/cm,d₃₃^*=1033pm/V,S=0.146%,H=6.5%.Comparing with 0.15PSN-0.52PMN-0.33PT ceramic,the d₃₃ is increased by about 77.7%.When the annealing temperature is 140℃,the remained d₃₃ can still maintains 73%of value before annealing,suggesting that the usable temperature range of this system is more wider than that of Sm-PMN-PT system.[001]orientated BaTiO₃ mirco-plates with a diameter-to-thickness ratio greater than 10 was prepared by topochemical conversion method.Then the 0.15PSN-0.52PMN-0.33PT and0.15PSN-0.54PMN-0.31PT textured ceramics were synthesized by templated grain growth using BaTiO₃ platelets as template.It is found that with the increase of template content,the ceramics structure transform to tetragonal phase gradually and the T_c decreases gradually.At the same time the d₃₃ increases firstly and then decreases with the increasing template content.For 0.15PSN-0.52PMN-0.33PT textured ceramic with 3 vol%template content,the F₀₀₁ is about 0.93 and the maximum value of d₃₃ is 680 p C/N,which is 1.4 times than as that of non-oriented counterpart.For 0.15PSN-0.54PMN-0.31PT textured ceramic with 3 vol%template content,F₀₀₁=0.94,T_c=152℃,P_r=23.55μC/cm~2,E_c=4.6 k V/cm,the maximum value of d₃₃ is 720 p C/N.Comparing with non-oriented ceramics,the d₃₃ is increased by 80%.When the annealing temperature is140℃,the remained d₃₃ can still maintain 81%of value before annealing.