Growth and Characterization of Na_0.5K_0.5NbO₃ Thin Films on Polycrystalline Pt₈₀Ir₂₀ Substrates

Abstract

Na0.5K0.5NbO3 thin films have been deposited onto textured polycrystalline Pt80Ir20 substrates using radio frequency magnetron sputtering. Films were grown in off- and on-axis positions relative to the target at growth temperatures of 500–700 °C and sputtering pressures of 1–7 Pa. The deposited films were found to be textured, displaying a mixture of two orientations (001) and (101). Films grown on-axis showed a prefered (001) orientation, while the off-axis films had a (101) orientation. Scanning electron microscopy showed that the morphology of the films was dependent on the substrate position and sputtering pressure. The low-frequency (10 kHz) dielectric constants of the films were found to be in the range of approximately 490–590. Hydrostatic piezoelectric measurements showed that the films were piezoelectric in the as-deposited form with a constant up to 14.5 pC/N.

Microstructure/dielectric property relationship of low temperature synthesised (Na,K)NbOx thin films

“…1. Hence, this may indicate that Pt 80 Ir 20 substrates promote the nucleation of the NKN phase due to the lattice match between the two materials [12]. Furthermore, the effect of the growth temperature on the lattice parameter of the NKN is also significant: Only the lattice parameter of the film deposited at 300 C is close to the bulk value [15], demonstrating the relevance of both the choice of substrate and growth temperature.…”

“…Furthermore, they observed a strong effect of the background oxygen pressure, with the morphology and electrical properties of the NKN films improving for higher oxygen pressures [11]. Wang et al reported on the growth of NKN films by RF magnetron sputtering on same substrates, for both on-and off-axis geometry, resulting in dielectric constants as high as 590 at 10 kHz and hydrostatic piezoelectric constants of 14.5 pC/N [12]. Also here, the films were grown at a high substrate temperature of 650 C and under the relatively high pressure of 7 Pa.…”

Potassium‐Sodium‐Niobate‐Based Thin Films: Lead Free for Micro‐Piezoelectrics

“…ε r of 580 and dielectric loss (tan δ ) values of 0.007 at room temperature were reported, and it should be noted that those results were measured based on interdigital capacitors. This work has been followed by further studying the microwave tenability of the dielectric permittivity in KNN films on various substrates, such as SiO 2 ‐suffered Si substrate, textured polycrystalline Pt 80 Ir 20 substrates . The ferroelectricity of these films has also been reported, but the hysteresis loops varied dramatically, which could originate from different film qualities, substrate, and electrode patterns .…”

Synthesis and Characterization of (K0.5Na0.5)NbO3Piezoelectric Ceramics Prepared Using K5.70Li4.07Nb10.23O30as a New Sintering Aid

“…KNN also has a morphotropic phase boundary composition of (K 0.5 Na 0.5 )NbO 3 similar to that of PZT and is therefore a promising lead-free material. KNN compounds are studied as thin films or in bulk ceramics [3][4][5][6][7][8][9][10][11][12][13]. However, the difficulty in sintering KNN under atmospheric conditions is a serious drawback.…”