Microstructure and electric properties of (Na0.85K0.15)0.5Bi0.5TiO3 composited films with alternative TiO2 layers

Abstract

AbstractIn this work, in order to investigate the effect of TiO2 layer on the microstructure and piezoelectric properties of (Na0.85K0.15)0.5Bi0.5TiO3 (NKBT) thin films, TiO2 layer was inserted at the interface between the NKBT thin film and substrate and on both sides of the NKBT, i.e., at the interface and on the top of the NKBT thin film. NKBT composited films with alternative TiO2 layer were deposited on Pt/Ti/SiO2/Si substrate by aqueous sol‐gel method. X‐ray diffraction observation found that the degree of (100) preferred orientation strengthened with TiO2 layers added, especially on both sides of NKBT thin film. The TiO2/NKBT/TiO2 composited film with both TiO2 layer of 40 nm thickness exhibited a remnant polarization value Pr of 22.6 μc/cm3 and effective piezoelectric coefficient of approximate 77 pm/V, which are much larger than that of the single‐layered NKBT thin film with Pr value of 13.7 μc/cm3 and of 56 pm/V, respectively. According to the investigation of the temperature‐dependent ferroelectric property, it was found that the Pr gradually increased, and in the meantime the coercive voltage gradually moved to higher voltage with testing temperature varied from 20 to −150°C. Besides, applied voltage dependence of leakage current density measurement indicated that the TiO2 layer would effectively lower the leakage current of the films, and the TiO2/NKBT/TiO2 composited film both TiO2 layer of 40 nm exhibited the lowest leakage current.