Bioactive potassium and sodium niobate (K_0.5Na_0.5)NbO₃ synthesized by solid-state reaction and sol-gel methods

This study proposes an innovative approach in the quest for piezoelectric materials, aiming to replace lead-based ceramics (PZTs), known for their high toxicity. Potassium sodium niobate (KNN) compounds were chosen as a promising alternative. While the synthesis of KNN via solid-state reaction (SSR) is common, maintaining the correct stoichiometry is challenging. In this work, we employed sol-gel (SG) and SSR methods for synthesis, combined with both conventional sintering techniques and spark plasma sintering. Comprehensive analyses were conducted, including crystal structure, microstructure, density, and piezoelectric properties, as well as bioactivity tests, among others. The results revealed that KNN samples exhibited remarkable piezoelectricity, coupled with surprising bioactivity, demonstrating good cell viability and resorption in a biological medium. Thoughtful selection of synthesis methods and variations in the sintering process were crucial in achieving high densification rates, enabling the investigation of the interplay between density and piezoelectric properties. Additionally, the application of polarization prior to immersion in a biological medium stimulated apatite precipitation. This indicates the promising application of these compounds as bioceramic devices.