A Study On (Bi_1/2Na_1/2) TiO₃-BaTiO₃ Of Lead-free Piezoelectric Ceramics

Lead-free piezoelectric ceramics materials, (1-x)(Bi1/2Na1/2) TiO3- xBaTiO3 (BNBT), were prepared by conventional piezoelectric ceramics technique. Their dielectric properties, piezoelectric properties and microstructure were systematically studied. The content of BaTiO3, phase transition and crystal structure were also mentioned.The influence of the calcining temperature on the properties of ceramics was studied. The scope of calcining temperature was determined by XRD of powder getting at different temperature. The proper calcining temperature was determined by testing properties.The influence of the grain size on the properties of ceramics was studied. The proper milling time was determined by means of laser granulameter and SEM. The proper moulding pressure was determined by investigating the probability of cracking as functions of moulding pressure.The proper sintering temperature and soaking time were determined by testing the properties of ceramics. The different sintering temperature was investigated by XRD. It found that BNBT-6 includes rhombohedral phase and tetragonal phase. With the increasing of sintering temperature and soaking time, the crystal size becomes more and more big by SEM observation. The composition of different crystal shape is different by EDS analyses.The proper poling field, poling time and poling temperature were determined by testing the properties of ceramicsEffects of the content of BaTiO3 in a wide range on the properties of the system were investigated. According to XRD patterns, the morphotropic phase boundary (MPB) lays in near x=0.06. The main physical properties of this system can reach optimum values near the MPB. According to SEM observation, the crystal size of the ceramics is inhibited with the increasing of the amount of Ba2+ addition.The crystal structures including phases, boundaries of grains and domains were investigated by using high-resolution transmission electron microscope (HRTEM).The results showed that BNBT crystal is pseudocubic and there is amorphous phase in the interphase.