Lead-free piezoelectric (K0.5Na0.5)NbO3 thin films derived from chemical solution modified with stabilizing agents

Abstract

( K 0.5 Na 0.5 ) NbO 3 (KNN)-based ferroelectric thin films were prepared by a chemical solution approach modified with both diethanolamine (DEA) and ethylenediaminetetraacetic acid (EDTA) as the stabilizing agents. The obtained KNN thin films exhibited a remarkably low leakage current and well-saturated polarization hysteresis loop. The effective piezoelectric strain coefficient d33 and voltage coefficient g33 under the clamping of the substrate were improved to 74.0 pm/V and 28.3 mm V/N, respectively. The reason for the superior properties was found that the addition of EDTA and DEA was effective in suppressing the volatilization of K and Na at moderate temperature before the crystallization.

Potassium–Sodium Niobate‐Based Lead‐Free Piezoelectric Ceramic Coatings by Thermal Spray Process

“…During the testing, an unipolar AC signal of 10 V amplitude at 1 kHz was applied to the sample. The effective piezoelectric coefficient d 33 value of the coating is 112 pm/V, which is substantially larger than the effective d 33 values of KNN‐based thin films and thick films ( d 33 = 40–84 pm/V) . It should be noted that the piezoelectric properties of the coatings were measured under the substrate clamping effect, and the actual d 33 without substrate clamping should be significantly higher, and probably close to the d 33 coefficient of bulk ceramics in similar composition ( d 33 = 200–300 pm/V).…”

“…It was reported that KNbO 3 single crystals are readily grown from melt with 2 to 4 mol% excess of K . As for volatility at high temperature, previous studies on sol–gel‐derived KNN‐based thin films reported the volatilization of alkaline composition during thermal processing . For synthesis of KNN‐based bulk ceramics, the volatilization of potassium is reported to be approximately two times higher than that of sodium .…”

“…The high piezoelectricity of the KNN‐based systems further enables the potential of replacing lead‐based piezoceramics, as stated in recent reviews . Significant progress has been made in KNN‐based piezoelectric thin films fabricated by solution deposition method . However, no progress has been made for forming piezoelectric ceramic coatings by thermal spray process as a method with the desirable high productivity, increased thickness range, and capability of large area coating for many industry applications.…”

Effects and Mechanism of Combinational Chemical Agents on Solution‐Derived K0.5Na0.5NbO3 Piezoelectric Thin Films

“…It was reported that for the solution‐derived KNN films, introducing selected chemical agents in the precursor solutions could suppress the loss of potassium and sodium in the resulting thin films . So far, many chemicals have been used as stabilizing chemical agents for producing KNN thin films, including acetylacetone (AcAc), polyvinylpyrrolidone (PVP), polyethylene glycol (PEG), diethanolamine (DEA), and ethylenediaminetetraacetic acid (EDTA) . KNN thin films with improved piezoelectric properties were obtained with the introduction of EDTA and DEA .…”

Room temperature ferromagnetism and magnetoelectric coupling in (K0.5Na0.5)NbO3 PLD nanocrystalline films

“…Most of the recent researches are focused on the modified KNN ceramics to improve their electrical properties [29][30][31][32][33][34][35]. In addition, many preparation techniques such as magnetron sputtering [36,37], pulsed laser deposition (PLD) [38,39], metal-organic chemical vapor deposition (MOCVD) [40], sol-gel methods [41,42] and chemical solution approach [43], have been employed to obtain KNN thin films with high quality. However, it is difficult to control the stoichiometric composition of the resulting KNN thin films due to the strong volatilization of K and Na during PLD, which, on the other side, can also be utilized to investigate the influence of cation vacancies on the magnetic properties of KNN films.…”