Strong emissions of blue–yellow–red regions of La and Ti modified KNaNbO₃ ferroelectric ceramics

In this work, the results of the study on the optical properties of the perovskite structure ABO₃ with La³⁺ substitution for ions K⁺ and Na⁺ in the A site and Ti⁴⁺ substitution for ion Nb⁵⁺ in the B site are presented. The ceramics were sintered at 1100 ℃ and 1190 ℃ and formed at 10 MPa and 80 MPa. Dense ceramics were obtained with 94% of the theoretical density. The piezoresponse force microscopy (PFM) showed needle-shaped grains with a size of 30 nm for the samples formed at 10 MPa at both sintering temperatures. Apparently, the high temperature and high pressure used in formation reduced the energy of the band gap (E_g) from 3.36 to 3.09 eV. Strong emissions to 2.19, 1.86, 2.5, and 2.31 eV were obtained by exciting the samples at 325, 373, 457, and 500 nm, respectively; these emissions corresponded to blue–yellow–red regions of the visible spectrum.