SYNTHESIS AND SPECTROSCOPIC STUDIES OF RARE EARTH DOPED KNN CERAMIC

Abstract

The lead-free ceramics potassium sodium niobate, KNN, (K0.5Na0.5NbO3) were synthesized by solid-state reaction method to study the effect of rare earth ions (Er3+) on structural, ferroelectric and optical properties. In order to explore how temperature affects crystal formation, the undoped KNN was calcined at various temperatures ranging from 700 to 900°C. The powder X-ray diffraction pattern revealed the absence of secondary phases, confirming the formation of pure KNN phase, which was calcined at 900°C for 3h and then sintered at 1100°C for 3h to form a single-phase perovskite crystal with orthorhombic geometry. The XRD spectra of Er3+ doped KNN showed no extra phases confirming the complete diffusion of Er3+ ions into the host lattice. The FTIR band at 486 cm-1 & 720 cm-1 showed the formation of a perovskite structure. The PL emission spectra at room temperature of sintered Er3+ doped KNN pellets at an excitation wavelength of 488 nm and 980 nm were analyzed. In emission spectra, strong green emission bands (528 and 549 nm) and somewhat faint red emission bands (662 nm) were found. The intensity of PL emission spectra using 980 nm wavelength was far much greater than 488 nm, and in the analyses of the effect of power of radiation, it was found that photoluminescence observed is a two-photon phenomenon. The ferroelectric PE loop at room temperature showed decent shapes with good remnant polarization. The energy storage capacity was calculated using the P-E loop; found to have increased from 52.7% for undoped KNN to 67.21% for KNN with optimal erbium concentration, i.e., x=3. KNN has excellent inherent piezoelectric capabilities, and by combining its optical and ferroelectric properties, this type of material may also have potential use as a multifunctional device.