Potassium Sodium Niobate Lead-free Piezoelectric Ceramics: Difficulties in the Processing and the Advantages of Iran: The Case of Iran and Slovenia

Among different groups of lead-free piezoelectric ceramics, potassium sodium niobate (KNN) has someinteresting properties which make it a promising substituent to lead-based piezoelectrics. One basic drawback in dealing with KNN is its sensitivity to the moisture. The aim of this study is to find out how the atmospheric conditions affect the properties of stoichiometric (K0.50Na0.50)NbO3. The results are based on the experiences of working in two different research institutes in Iran and Slovenia, with the average annual relative humidity of 53 and 78 % in 2014, respectively. The average relative density of sample synthesized/sintered in Iran and Slovenia were 94.0 and 91.5 %, respectively. In order to further increase the density of sintered samples, a pre-annealing step for 4 h at 450 ˚C was introduced to the sintering curve in Slovenia and sintering was carried out in a completely open crucible configuration. These caused the density of samples to increase to 93.4 %. Measuring the dielectric loss versus temperature showed a remarkable increase upon cooling from 100 ˚C to room temperature, which could be attributed to the absorption of the humidity by sample. The results of this study showed that choosing a less-humid environment will allow easier handling in the process and less difficulties in the electrical characterization of final KNN products.