Effect of oxygen pressure on preferential orientation, microstructure and functional properties of Bi1.5MgNb1.5O7 thin films prepared by pulsed laser deposition

Polycrystalline bismuth magnesium niobate (Bi1.5MgNb1.5O7, BMN) thin films have been prepared by pulsed laser deposition at oxygen pressures in the range of 1-30 Pa. The degree of preferred orientation initially decreases and then increases as oxygen pressure is increased, as evidenced by X-ray diffraction measurements, revealing that a process of abnormal grain growth has occurred. The microstructures and dielectric properties of the BMN thin films are strongly dependent on the degree of preferred orientation which is influenced by oxygen pressure. The BMN thin films deposited at oxygen pressure of 10 Pa have the minimum degree of preferred orientation, while the thin films exhibit the highest dielectric tunability, the biggest dielectric constant and the lowest loss tangent. In addition, the frequency dependence of dielectric constant and loss tangent of BMN thin films deposited at different oxygen pressure is investigated as well.