Structural and optical properties of Pb₂KNb₅O₁₅ and GdK₂Nb₅O₁₅ tungsten bronze thin films grown by pulsed laser deposition

Lead potassium niobate Pb₂KNb₅O₁₅ (PKN) and gadolinium potassium niobate GdK₂Nb₅O₁₅ (GKN) thin films were grown on (001)MgO single crystal substrates using pulsed laser deposition technique. PKN and GKN thin films were characterized by X-ray diffraction and their linear optical properties were determined. The out-of-plane orientation of PKN thin film depends on the oxygen pressure used during the growth process: [001] for low pressure and [530] for high pressure. In contrast, GKN thin film is oriented [001] and is less sensitive to pressure. PKN and GKN thin films were found transparent and their refractive index quite similar to that reported on TTB-type ferroelectric oxides. GKN film exhibits high bandgap compared to the PKN film. - Highlights: • PKN and GKN oriented films were successfully grown by PLD on MgO substrate. • Their optical transmission was investigated. • Their refractive index and bandgap were determined.