Effect of NiO Sintering Aid on the Electrical Properties of KNN-LST Lead-free Piezoceramics

The current research focuses on the synthesis and characterization of sodium potassium niobate (KNN), a lead-free piezoelectric compound. The objective is to replace lead-based compounds like PZT using KNN-LST, which is sodium potassium niobate piezoceramic powder doped with lithium, antimony, and tantalum. To this end, solid-state method was employed to sinter the samples at ۱۱۱۰ °C with varying percentages of NiO sinter aid (۰%, ۰.۷۵%, ۱.۵%, and ۲.۲۵%). X-ray diffraction analysis confirmed the formation of pure KNN-LST perovskite phase at ۱۱۱۰ °C with a composition containing ۱.۵% NiO. Scanning electron microscope images also demonstrated that cubic particles inherent in KNN were observed in samples with no NiO addition as well as those containing ۰.۷۵% and ۱.۵% NiO; however, these particles were transformed into cylindrical grains when incorporating ۲.۲۵% NiO. With an increase in the sintering percentage from zero NiO content to higher amounts, sample density also increases from approximately ۸۵% up to its peak at around ۹۴%, followed by a slight decrease by about ۹۱%. Similarly, the dielectric coefficient increased from approximately۸۵۰ without any contribution from NiO sinter addition up to۱۵۰۰ upon addition of ۱.۵%NiO sinter but then, it decreased again by approximately ۱۲۰۰ followed by addition of ۲.۲۵% NiO sinter. Conversely, dielectric loss initially reduced from roughly ۰.۱۴% during no NiO sinter addition by merely ۰.۰۴% during ۱.

کلیدواژه ها:

Piezoelectric ، KNN ، Solid-State ، Microstructure