KNN–Eu transparent ferroelectrics: Local structure and luminescent property

Abstract Differ from the rapid development of piezoelectricity in potassium sodium niobate (KNN) ceramics, the progress of photoluminescence in transparent KNN ferroelectric ceramics remains stagnant. Herein, europium (Eu)‐doped KNN ceramics have been prepared to investigate its local structure and optical–electrical multi‐functionality. Both enhanced piezoelectricity in ceramics with a bimodal distribution of grain size and improved luminescent property in ceramics with refined grain size can be achieved by adjusting the content of Eu. The addition of Eu can destroy long‐range ferroelectric orders, leading to the formation of pseudo‐cubic phase and polar nanoregions (PNRs). The highly activated PNRs promoted electric field‐induced domain switching and nearly reversible piezo/ferroelectric properties. First‐principles calculations show that Eu substitution will lead to local inhomogeneous chemical bond environment, affecting the local electric/elastic fields and crystal fields, and then benefiting to the luminescence behavior, including both the intensity and lifetime. We believe that this work can benefit to the development of KNN transparent luminescent ceramics and the light‐emitting devices.