Effect of nano and micron WO۳ on microstructure and electrical properties of lead free potassium sodium niobate piezoceramics

Lead free potassium sodium niobate (KNN) piezoceramics were synthesized via conventional solid state sintering route. Nano and micron WO۳ were separately added to KNN through ball-milling. Dielectric and piezoelectric properties of samples sintered in the temperature range of ۱۱۱۰°-۱۱۴۵°C were measured by precision LCR-meter and APC d۳۳-meter devices. The results revealed that micron WO۳ particles were effective in inhibiting the grain growth in KNN ceramics. Micron WO۳-added KNN obtained much finer microstructure and the sintering process terminated at higher temperature compared to pure KNN and nano WO۳-added KNN. Densification and electrical properties of KNN were considerably affected by using nano and micron WO۳. Nano WO۳-added KNN obtained its maximum density at lower sintering temperature compared to micron WO۳-added KNN. With increasing the sintering temperature over optimum amounts, the density of both WO۳-added KNN samples decreased due to the evaporation of alkalis. Finally, at ۱۱۲۵ºC KNNW۳n showed d۳۳, εr, tanδ, and Qm of ۷۵ pC/N, ۳۴۵, ۲%, and ۵۰, respectively. For KNNW۳m sample at ۱۱۳۵ºC these values were ۸۱ pC/N, ۷۷۳, ۳.۳%, and ۳۰, respectively.

کلیدواژه ها:

Lead free piezoceramics ، Potassium sodium niobate ، Nano and micron WO۳ ، Microstructure ، Sintering process ، Electrical Properties