Fabrication of [Li_0.05(K_0.5Na_0.5)_0.95]NbO₃ transparent ceramics using conventional sintering technique

Abstract

The effect of Bi₂O₃ content on the crystal structure, microstructure, and optical and electric properties of [Li_0.05(K_0.5Na_0.5)_0.95]NbO₃ + x wt %Bi₂O₃ ceramics was investigated. These ceramics were fabricated using a conventional pressure-less sintering, and were observed to be opaque at x = 0 and 3 but transparent at x = 5 and 7. The transmittance at an infrared wavelength of 1310 nm was 68 and 62% at x = 5 and 7, respectively. At x = 5, a high Curie temperature of 365°C, a ferroelectric polarization–electric field loop with a reduced remanent polarization, and a quadratic electro-optic effect of 3.1 × 10⁻¹⁷ m²/V² were observed. The effective linear electro-optic effect (Δn/E_π) was calculated by the birefringence (Δn) divided by a half-wave electric field (E_π) of 43.2 kV/cm. This value was equal to 146 pm/V, which was higher than the linear electro-optic effect of previously reported (K,Na)NbO₃-based transparent ceramics and a LiNbO₃ single crystal. However, it was lower than that of a K(Ta,Nb)O₃ single crystal and (Pb,La)(Zr,Ti)O₃ transparent ceramics.