Effects of heat treatment on electrical and electromechanical properties of hydrothermally synthesized epitaxial (K_0.51Na_0.49)NbO₃ films

Abstract

Effects of heat treatment on the electrical and electromechanical properties of hydrothermally synthesized epitaxial (K0.51Na0.49)NbO3 films were investigated. The film composition and crystal structure did not markedly change with heat treatment from 240 to 600 °C in O2 atmosphere. However, the leakage current density drastically decreased from the order of 101 to 10−5 A/cm2 at 50 kV/cm after heat treatment at 240 °C. The relative dielectric constant, remanent polarization, and transverse piezoelectric constant increased with increasing heat treatment temperature from 300 to 600 °C (from 330 to 750 in εr, from 5.4 to 14 µC/cm2 in remanent polarization, and from 41 to 56 pm/V in transverse piezoelectric response). H2O desorption of 12 ppm was detected in epitaxial (K0.51Na0.49)NbO3 films by thermal desorption spectroscopy measurement. Such H2O desorption can be related to the improvement of the electrical and electromechanical properties of the hydrothermally synthesized epitaxial (K0.51Na0.49)NbO3 films.

Potassium–Sodium Niobate Lead-Free Piezoelectric Materials: Past, Present, and Future of Phase Boundaries

“…Since the increase in interest in the piezoelectric activity of KNN-based ceramics, efforts have been made to prepare corresponding thin films due to their potential applications for microdevices such as microelectromechanical systems. − However, two main issues still hinder the fabrication of high-quality KNN-based films: (i) composition deviations from stoichiometry and (ii) the loss of alkali oxides during preparation. ,,, Table lists the preparation methods and the corresponding electrical properties of KNN-based materials in the form of thin films or thick films. − One can observe from Table that the ferroelectric and piezoelectric properties of KNN-based materials (e.g., thin film and thick film) can be promoted to varying degrees by some methods, such as the use of stabilizing agents, new preparation techniques (hydrothermal method), excess alkali metals, , different substrates, −…”

“…Although the ferroelectric and piezoelectric properties of KNN-based films can be improved by these methods, − their electrical properties are still poor when compared to lead-based or the corresponding bulk materials. Unlike KNN-based bulk materials, it is difficult to form phase boundaries in the corresponding material system. − In the past, researchers have attempted to construct phase boundaries in KNN-based thin films using the phase boundary compositions of the corresponding bulk materials, − but the results are disappointing due to a number of factors (e.g., composition deviations, lattice mismatch between thin film and substrate, etc.).…”

Ferroelectric and piezoelectric properties of KNbO3films deposited on flexible organic substrate by hydrothermal method

“…We have already reported the successful growth of ferroelectric (K x Na 1¹x )NbO 3 films at 240 °C on (100) c -SrRuO 3 //(100)SrTiO 3 substrates by the hydrothermal method, [31][32][33][34][35][36] where (K x Na 1¹x )NbO 3 does not include the Ti element in the constituent elements. Moreover, we clarified the effect of the top layer of the substrate to deposit (K x Na 1¹x )NbO 3 films by the hydrothermal method.…”

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

“…In order to more accurately understand the ferroelectric properties of hydrothermally-synthesized (K,Na,Li)NbO 3 films, it is necessary to improve the insulation by additional treatment, such as post-annealing. 31)…”