Chemical Solution Processing and Characterization of La Doped Tungsten Bronze K0.4(Pb0.6Ba0.4)0.8Nb2O6 Thin Films

Abstract

Crack-free La doped K0.4(Pb0.6Ba0.4)0.8Nb2O6 (KPBLN) thin films have been synthesized by the chemical solution process. Transparent tungsten bronze K0.45(Pb0.6Ba0.4)0.7La0.05Nb2O6 (KPBLN60/5) thin films were fabricated on fused silica substrates at 700°C. KPBLN60/5 thin films on MgO(100) and Pt(100)/MgO(100) also crystallized in the tungsten bronze single phase with c-axis preferred orientation. Incorporation of La ions in KPBN60 was found to be effective in forming the tungsten bronze phase and improving the surface morphology of the synthesized films on the substrates. The propagation modes in the KPBLN films were observed via the prism coupling method, using a He–Ne (632.8 nm) laser beam. The Curie temperature (Tc) of the KPBLN60/5 thin film on a Pt(100)/MgO(100) substrate was around 280°C. The dielectric constant of the KPBLN60/5 film at Tc was about 3000. The KPBLN60/5 thin film on Pt(100)/MgO(100) showed a spontaneous polarization of 22 µC/cm2, a remanent polarization of 17 µC/cm2 and a coercive field of 84 kV/cm at -140°C.