Dielectric and structural characterization of KNbO3 ferroelectric thin films epitaxially grown by pulsed laser deposition on Nb doped SrTiO3

KNbO3 thin films were deposited on SrTiO3 substrates by pulsed laser deposition. The X-ray diffraction patterns highlight an epitaxial growth according to the (011) orientation. This epitaxial growth was then confirmed by Electron Channeling Pattern. In agreement with the structural characteristics the dense microstructure consists in regular and ordered grains. Dielectric measurements were performed in the 20 Hz to 1 MHz frequency range on a KNbO3 thin film grown on 2 at.% Nb doped (100)SrTiO3 substrate in a large range of temperature in order to investigate the paraelectric–ferroelectric transition. Measurements at room temperature revealed a dielectric constant of 450 at 10 kHz and a minimum value of the loss tangent of 0.075 at 100 kHz. Dielectric study in the 20–600 °C temperature range showed a maximum of permittivity at the Curie temperature Tc = 410 °C and evidenced a “progressive” first-order phase transition, different from the classical “diffuse” transition.