Effect of Mn doping on the leakage current and polarization properties in K_0.14Na_0.86NbO₃ ferroelectric single crystals

Abstract

Single crystals of K 0.14 Na 0.86 NbO 3 (KNN) and Mn-substituted KNN (Mn-KNN, K 0.14 Na 0.86 Mn 0.005 Nb 0.995 O y ) were grown by a flux method, and the effects of Mn substitution on the leakage current, polarization and dielectric properties were investigated along [100] cubic . As-grown and annealed (850°C in air) crystals did not show an apparent polarization hysteresis loop due to its large leakage current density (³10 ¹3 A/cm 2 ). The annealing at 1100°C in air led to a marked decrease in leakage current density of the order of ³10 ¹6 A/cm 2 for KNN crystals. Mn-KNN crystals annealed at 1100°C in air exhibited a low leakage current density of ³10 ¹8 A/cm 2 . Electron spin resonance measurements and defect chemistry analysis show that the average valence increase of Mn by oxidation treatment (the annealing in air) absorbs electron hole, the carrier of the leakage current, which is suggested to be the origin of the low leakage current observed for Mn-KNN crystals.

Ferroelectric domain structures in <001>-oriented K0.15Na0.85NbO3 lead-free single crystal

“…5 Besides KNN ceramics, the KNN-based single crystals have been grown to further improve the piezoelectric properties, because single crystals can be poled along different directions by domain engineering method. [6][7][8][9] The behavior of a ferroelectric is mainly dependent on the local domain response by applying an electrical loading. Therefore, the domain structures are very important for investigating the ferroelectric performance of the single crystal.…”

Structural phase transitions and electrical properties of (K Na1−)NbO3-based ceramics modified with Mn

“…20 Decreased leakage current and high current densities 21,22 When used to dope (K 0.5 Na 0.5 ) 0.935 Li 0.065 NbO 3 ceramics, no significant change on the crystal structure was observed and hard ferroelectric effects were observed due to oxygen vacancies. 23 A change of valence state from Mn 4+ to Mn 3+ has been observed using synchrotron X-ray absorption spectroscopy for (K 0.5 Na 0.5 Li 0.065 )NbO 3 doped with Mn and the phase was identified to be tetragonal.…”

Lead-Free KNN-Based Piezoelectric Materials

“…Figure 5.8 shows the P-E hysteresis loop of a 0.5 mol% Mn-doped KNN single crystal grown by the flux method with remnant polarization of 52 mC cm À2 which is one of highest values reported for KNN-based materials [71]. Mn-substitution in K 0.14 Na 0.86 NbO 3 single crystals also provides superior polarization and reduces the leakage current [73].…”

“…The highest resistivity is achieved in the Mn-KNN crystal grown by flux method and annealed at 1,100 C in an air atmosphere which shows a well-saturated hysteresis loop with a remanent polarization of 40 mC cm À2 and coercive field of 12 kV cm À1 [65]. KNN crystals by flux method have also been grown by some other groups [69,71,73]. Figure 5.8 shows the P-E hysteresis loop of a 0.5 mol% Mn-doped KNN single crystal grown by the flux method with remnant polarization of 52 mC cm À2 which is one of highest values reported for KNN-based materials [71].…”