Optical and electrical properties of pressureless sintered transparent (K0.37Na0.63)NbO3-based ceramics

Lead-free (1−x)(K0.37Na0.63)NbO3-xCa(Sc0.5Nb0.5)O3 (x=0.050, 0.070, 0.090, 0.095 and 0.100) transparent ferroelectric ceramics have been fabricated by pressureless sintering procedure. Transmittance of 0.91(K0.37Na0.63)NbO3-0.09Ca(Sc0.5Nb0.5)O3 ceramics sintered in sealed alumina crucible was 15% higher than those sintered unsealed in air. By increasing the content of Ca(Sc0.5Nb0.5)O3, the phase structure of (K0.37Na0.63)NbO3 ceramics transformed from orthorhombic to tetragonal symmetry first and then to pseudo cubic symmetry. The 0.91(K0.37Na0.63)NbO3-0.09Ca(Sc0.5Nb0.5)O3 ceramics exhibited high density (98%), high transmittance (60%) in the near-IR region and relatively good electrical properties (εr=1914, tanδ=0.037, Tc=147 °C, Pr=6.88 μC/cm2, Ec=8.49 kV/cm). Meanwhile, the introduction of Ca(Sc0.5Nb0.5)O3 induced a composition fluctuation in the (K0.37Na0.63)NbO3 lattice and made the ceramics more relaxor-like, which would lead to a further reduction of light scattering. These results demonstrated that 0.91(K0.37Na0.63)NbO3-0.09Ca(Sc0.5Nb0.5)O3 could be promising lead-free transparent ferroelectric ceramics.