A relationship between defect engineering and pyroelectric response mechanism of Mn‐doped KNN‐based ceramics

Abstract In this work, 0.995(K 0.48 Na 0.52 ) 0.95 Li 0.05 NbO 5 ‐0.005BiAlO 3 ‐ x mol% MnO 2 (KNLN‐BAO‐Mn‐ x ) pyroelectric ceramics were synthesized by solid‐state reaction method. Coexistence of orthorhombic phase (O phase) and tetragonal phase (T phase) were observed for all studied ingredients at ambient temperature. The pyroelectric performance was obviously influenced by Mn ions due to its variable roles in the ceramics. The ceramic ( x = 0.1) presented largest p value ( p ∼3.19 × 10 −4 C m −2 K −1 at 25°C) with better F i 1.746 × 10 − 10 mV −1 , F v 0.023 m 2 C −1 and F d 1.134 × 10 −5 Pa −1/2 , indicating a potential candidate for pyroelectric infrared radiation detectors. Further, the effect of Mn‐related defect dipoles on pyroelectric response were clarified. Trace Mn dopants ( x = 0.1) acted as donors increased the pyroelectric response at ambient temperature due to enhanced spontaneous polarization via suppressing defect dipoles and oxygen vacancy in bulks. Nevertheless, the pyroelectric performances for ceramics with excess MnO 2 ( x ≥ 1.0) were extensively weakened for hard ferroelectric effect of Mn ions‐related defect dipoles, which was demonstrated via the thermal stimulated depolarized current (TSDC) spectroscopy. Meanwhile, the effects of Mn ions on AC impedance behaviors of ceramics were systematically investigated. The conductive mechanism for undoped and doped ceramics were explored. In a word, a proof of the donor effect of Mn ions in perovskite ferroelectrics via the thermal stimulated current (TSC) current method had been provided. It is believed that this work was worthwhile for helping to deeply understand interactions between defects and pyroelectric performance in KNN‐based ceramics.