Electrical property and phase transition analysis of KNN-based lead-free ferroelectric films

Abstract

The electrical properties, phase construction, thermal stability and phase transition behavior are investigated in 0.95(K0.49Na0.49Li0.02)(Ta0.2Nb0.8)O3–0.05BaZrO3 with 2 wt% MnO2 (KNNLT-BZM) lead-free epitaxial ferroelectric film on LaNiO3 (LNO)-coated SrTiO3 (STO) (001) substrate. The x-ray diffraction results show that a mixed orthorhombic (O) and tetragonal (T) phase is obtained in KNNLT-BZM film. The MnO2 doping can effectively suppress its leakage current, which greatly improves the electrical performance featured by a lower leakage value of 8 × 10–11 A cm−2, a twice remnant polarization of 44.7 μC cm−2, and frequency-dependent ferroelectricity between 50 Hz and 10 kHz. Strikingly, the KNNLT-BZM film maintained ferroelectric nature up to 200 °C, and exhibit a phase transition from O + T mixed phase to T phase (T Mix-T) at 300 °C with a high Curie temperature above 440 °C. These results suggest great application potentials of KNN-based films in lead-free micro-electronic devices.