Construction Of Ceramic Injection Molding Platform And Preparation Of 0.94NBT-0.06BT Piezoelectric Ceramic System

Ceramic injection molding?CIM?technology is a branch of powder injection molding?PIM?technology.It is a new type of advanced manufacturing technology developed rapidly in recent years and has been paid lots of attention and studied wildly by domestic and international scholars.The technology add a certain amount of binder to make the powder material have a certain degree of fluidity,and the injection molding method is used to make the material product which is a method for forming plastics with near net size.Na_0.5Bi_0.5TiO₃-BaTi O₃?NBT-BT?lead-free piezoelectric ceramic system has high piezoelectric and ferroelectric properties,and that is considered to be the most likely substitute for Lead-based ceramics such as PZT.Lead-free piezoelectric materials are expected to exhibit superior piezoelectric performance over lead-based ceramics near the morphotropic phase boundary?MPB?component,its system is 0.94NBT-0.06BT.Therefore,it is meaningful to carry out the preparation of lead-free piezoelectric ceramics with 0.94NBT-0.06 BT system in terms of basic theory and application prospects.Based on the ceramic injection molding technology,this thesis has developed a small injection molding equipment which suitable for the laboratory and completed the construction of the experimental platform.Mold flow analysis software was used to analyze the molding process to determine the relative parameters of the molding.The device has been declared national invention patent?application number:201710538628.0?.At the same time,0.94Na_0.5Bi_0.5TiO₃-0.06BaTiO₃ was selected as the research system.Firstly,BaTiO₃ template was prepared by two-step molten salt method.Then the traditional solid phase sintering method,BaTiO₃ template introduction method,no electric field injection molding and electric field injection molding were used respectively.Lead-free piezoceramics of 0.94Na_0.5Bi_0.5Ti O₃-0.06BaTiO₃ system were prepared by injection molding and injection molding under four different injection molding processes,combined with X-ray diffraction?XRD?,scanning electron microscopy?SEM?,piezoelectric constant measurements,dielectric constant testing,density calculation and other methods to analyze the micro-morphology,phase composition and performance.The results showed as follows:?1?The BaTiO₃ template was prepared by two-step molten salt method.The relationship among the sintering temperature,the morphology and size of BaTiO₃crystallites was studied by taking NaCl as the molten salt and the mass ratio of molten salt to the reactants is 1:1.The analysis results show that the increase of synthesis temperature is conducive to the growth of flake grains,but does not change the phase structure of the product.The synthesis reaction at a temperature higher than 1050°C,the morphology of the resulting product has changed significantly,it will produce rod-like grains.Synthesis of flaky BaTiO₃ more ideal condition is that NaCl as a molten salt,the mass ratio of molten salt and the reactants is 1:1,the synthesis temperature is 1050°C,holding time is 3h.?2?Compared with the traditional solid-phase sintering method,the BaTiO₃template prepared by the introduction of ceramic particles uniform size become larger,grain gap become smaller and ceramic density increased.Two preparation processes are are formed morphotropic phase boundary in which trigonal and tetragonal phases coexist.However,the bimodal diffraction intensity and peak width of samples prepared by BaTi O₃ template introduction are better than those obtained by traditional solid-phase sintering.The XRD patterns show that the samples prepared by both methods have BaTiO₃,and the presence of the original powder measured in the resulting product should consider whether the reaction is fully complete.The piezoelectric constant of the prepared ceramic sample by BaTi O₃ template is higher than that of the conventional traditional solid-phase sintering method.The maximum value of d₃₃ obtained by the traditional solid-phase sintering method is 103pC/N,the dielectric constant is 1050;the maximum value of sample d₃₃ prepared by BaTiO₃ template introduction method is 126pC/N;the dielectric constant is 1283.?3?Compared with the preparation of non-electric field injection molding,the 0.94Na_0.5Bi_0.5TiO₃-0.06BaTiO₃ ceramic prepared by the injection molding of an electric field has grown,the porosity decreases and the density of the ceramic increases.The maximum value of d₃₃ is 101pC/N,and the dielectric constant is1029.The maximum value of d₃₃3 is 141p C/N,and the dielectric constant is 1436when the electric field was applied.?4?The piezoelectric properties of 0.94Na_0.5Bi_0.5TiO₃-0.06BaTiO₃ ceramics prepared by injection molding under non-electric field have no significant change compared with the traditional solid-phase sintering method,but lower than that of ceramics prepared by BaTiO₃ template introduction method.Injection molding under the applied electric field,the piezoelectric properties of the prepared ceramic samples are optimal,but the binder cannot be completely eliminated,affecting the microscopic morphology of the ceramic grains.