Titanium Diffusion into (K_0.5Na_0.5)NbO₃ Thin Films Deposited on Pt/Ti/SiO₂/Si Substrates and Corresponding Effects

Abstract

Lead-free (K 0.5 Na 0.5 )NbO 3 (KNN) thin films were prepared on Pt/Ti/SiO 2 /Si substrates by a sol-gel processing method, and titanium diffusion from the substrates into the KNN films under different thermal treatment conditions were investigated by the secondary ion mass spectroscopy depth profile and X-ray photoelectron spectroscopy surface analysis. Titanium diffusion was evident in all the KNN thin films, which was further aggravated not only by increasing the annealing temperature, but also surprisingly by higher ramping rate attributed to the resulting larger grain boundaries. The pronounced effects of the titanium diffusion and the resulting substitution of Ti 41 for Nb 51 with different valence states on the composition, structure, and electrical properties of the KNN thin films are analyzed and discussed. The results showed that the Ti diffusion from the substrate played a crucial role in affecting the structure and electrical properties of the ferroelectric KNN thin films deposited on Pt/Ti/SiO 2 /Si substrate.

Effect of Ti on the properties of (KxNa1−x)NbO3 based lead-free ceramics

“…This is possibly due to the low reactivity between the Ti ions and the elements in KNN ceramics making it difficult for effective diffusion to take place. Excess titanium in KNN thin films has been reported to diffuse to the grain boundaries affecting the properties of this material [17].…”

“…It diffused into the films produced from the sol-gel method and deposited on Pt/Ti/ SiO 2 /Si substrate. The evaporation loss associated with the alkali ions was minimized across the thickness of the films [17]. The addition increased the leakage current by one order of magnitude when used to dope KNN-LiSbO 3 -LiTaO 3 thin film on SrTiO 3 substrate and deteriorated its ferroelectric properties [18].…”

Effect of A-Site Ion Excess on (K, Na)NbO3 Thin Film Fabricated by Sol–Gel Non-alkoxide Process

“…The films are dense, while the grain size of K 0.6 Na 0.5 NbO 3 is smaller, which indicates that K excess can restrain the growth of the grains. The possible reason is that the volatilization of excessive K ions promotes a large amount of Ti ions diffuse from the substrates into the films which accumulate around the grain boundaries and restrain the growth of grains (Goh, Yao, and Chen 2009). Figure 3 shows the P-E hysteresis loops and dielectric constant (K) of K 0.6 Na 0.5 NbO 3 , K 0.5 Na 0.6 NbO 3 and K 0.5 Na 0.5 NbO 3 thin films.…”

Development of lead-free materials for piezoelectric energy harvesting

“…Volatility of the alkali species at high temperatures [7], hygroscopic nature of the reactant powders [8] and relatively low piezoelectric coefficient (d 33 ) ~ 80 pC/N are its drawbacks. Various methods to overcome the drawbacks pertinent to KNN have been undertaken by several authors [9][10][11][12].…”