A study on the piezoelectric and dielectric characteristics of lead free (Na,Li) NbO3

Compared with electromagnetic motor ultrasonic motor have many merit such as no electromagnetic noise, rapid response, precision control and compact size, etc. So, many difference type of ultrasonic motor have been design and developed. PZT ceramics has long been used for ultrasonic motor application due to the excellent piezoelectric property. However, it is well known that PZT based ceramics are environmental burdened materials because of during the sintering process. Therefore, a research about the development of lead-free ceramics and a method protecting the evaporation of PbO has been the most important issue to current researchers. Accordingly, a study on the lead-free piezoelectric ceramics has been performed very enthusiastically because of a need for the environmental-friendly ceramics. The lead-free ceramics generally shows the low sinterability and weakens piezoelectric properties compared to PZT system ceramics. Hence, In this study, in order to develop the composition ceramics for lead-free ultrasonic motor, (1-x-0.09)NaNbO3+xBaTiO3+0.09LiNbO3 ceramics were fabricated using a conventional mixed oxide process and their piezoelectric and dielectric characteristics were investigated according to the BaTiO3 substitution. BaTiO3 substitution enhanced density, dielectric constant(åμr) and electromechanical coupling factor(kp). However, mechanical quality factor was deteriorated. At the BaTiO3 substitution of 4mol%, density, electromechanical coupling factor(kp), dielectric constant(åμr) and piezoelectric constant(d33) of specimen showed the optimum value of 4.493g/cm3, 0.236, 175, 70pC/N, respectively.