Low-temperature deposition of Li substituted (K,Na)NbO₃ films by a hydrothermal method and their structural and ferroelectric properties

Abstract

Li substituted (K,Na)NbO 3 films with K-rich composition against polymorphic phase boundary were deposited at 240°C on (100)La:SrTiO 3 substrates by hydrothermal method. The amount of Li content in films was controlled by changing the nominal composition of raw materials, A = [LiOH]/([KOH] + [NaOH] + [LiOH]). X-ray diffraction measurement showed that {001} c-oriented epitaxial (K,Na,Li)NbO 3 films were obtained for all nominal compositions (A = 00.1). However, the diffraction peaks originated from a secondary phase were also detected in the range of A = 0.050.1. Plan-view scanning electron microscopy observation revealed that (K,Na,Li)NbO 3 films possessed square-shape feature in accordance with the epitaxial relationship between film and substrate, while the secondary phase exhibited triangular-and pyramid-shaped features. The distribution of the elements across the thickness was investigated by time-of-flight secondary ion mass spectrometry. Transmission electron microscopy revealed the columnar structure of the film. In addition, nanoscale-pores have been found to exist in the boundary of each column by scanning transmission electron microscopy. (K,Na,Li)NbO 3 films, A up to 0.03, showed ferroelectricity, and the maximum remanent polarization was observed at A = 0.01.

Perovskite Oxides Prepared by Hydrothermal and Solvothermal Synthesis: A Review of Crystallisation, Chemistry, and Compositions

“…Mixed tantalate-niobates have also been prepared using hydrothermal approaches. [158] Other substitutions in the this family of perovskites include lithium, in (Na,K)NbO3-LiTaO3 thin films, [159] and also epitaxial (K,Na,Li)NbO3 films which were grown hydrothermally on (100)-La:SrTiO3 substrates to give layers that showed ferroelectric hysteresis loops, [160] and sulfur-containing NaTaO3 produced directly by use of Na2S2O3•5H2O as a hydrothermal reagent. [161] Other niobates whose hydrothermal synthesis has been studied include AgNbO3, whose photocatalytic properties have been studied, [162] and Pb(Mg1/3Nb2/3O3), which was formed at high KOH concentrations in preference to a pyrochlore phase.…”

Low-Temperature Solution Approaches for the Potential Integration of Ferroelectric Oxide Films in Flexible Electronics

“…But, this does not occur on polymer (or amorphous) ones, where seed (nucleation) layers have to be previously deposited on the surface of the substrate. [39][40][41][42][43][44][45][46] To the knowledge of the authors, only Shiraishi et al have reported the Hydrothermal preparation of KNbO 3 (KNN) ferroelectric thin films on flexible polysulfone substrates with a remanent polarization of P R 4.2 µC cm -2 . [39] In this work, a LaNiO 3 perovskite seed layer is deposited by RF-magnetron sputtering on the electroded substrate (Pt/Ti/polysulfone), before the growing of the ferroelectric perovskite.…”

“…1). [11,12,14,39,40,44,46, Fukushima et al, [74] and Budd et al, [75,76] were among the first that demonstrated the successful fabrication of ferroelectric oxide thin films (PbTiO 3 , Pb(Zr,Ti)O 3 , PZT and 2014 [39] 2010 [46] 2019 [40] 2017 [44] 2017 [73] 2015 [72] 2014 [11] 2020 [71] 2011 [63][64][65] 2014 [62] 2008 [68] 2010 [67] 1999 [61] 2020 [70] 2003 [69] 2004 [12] 2000 [66] 2014 [62] 2016 [58] 2008 [57] 2017 [56] 2008 [14] 2001 [60] 2013 [59] 2018 [52] 2003 [53] 2000 [54] 2009 [55] The graphic shows the ferroelectric composition of the film, the processing temperature at which they were processed and the ferroelectric remanent polarization (PR) measured in them. The CSD strategy/ies used for the low-temperature solution processing of the films are also shown.…”

Effect of Ta-substitution on the deposition of (K,Na)(Nb,Ta)O3 films by hydrothermal method

“…In this regard, hydrothermal method is a low temperature deposition technique, with which one can deposit (K,Na)NbO 3 -based films. [16][17][18][19][20][21][22][23] This method is a simple wet process using alkaline source solutions and oxide powders with process temperatures below 300 °C, which is much lower than those of other deposition methods. In our previous study, it was found that K-rich (K x Na 1−x )NbO 3 films (x = 0.8-0.9) deposited by the hydrothermal method exhibited physical and electrical characteristics suitable for applications to various piezoelectric devices.…”

“…For example, Handoko et al reported the hydrothermal synthesis of (K,Na)NbO 3 -LiTaO 3 films. 26) However, there are a few reports on the hydrothermally-deposited (K,Na)NbO 3 -based films, 22) and the effect of elemental substitution on the physical and electrical properties of these films is unclear.…”