Preparation of Barium Titanate–Potassium Niobate Nanostructured Ceramics with Artificial Morphotropic Phase Boundary Structure By Solvothermal Method

Abstract

Barium titanate (BaTiO3, BT)–potassium niobate (KNbO3, KN) (BT–KN) nanostructured ceramics with a distorted interface region, i.e., artificial morphotropic phase boundary (MPB) structure, were prepared by the solvothermal method. The results of the optimization of reaction conditions showed that the metastable region of only KN crystal growth was obtained using a mixture of KOH and K2CO3 as the K source and Nb2O5 as the Nb source in ethanol. Moreover, KN formation under the metastable region using a particle compact composed of a mixture of BT and Nb2O5 particles as substrates resulted in the successful preparation of BT–KN nanostructured ceramics with an artificial MPB region and a porosity of around 35%. This is the first report on the preparation of ceramics with a heteroepitaxial interface between BT and KN below 230 °C.

Tailoring of unipolar strain in lead-free piezoelectrics using the ceramic/ceramic composite approach

“…[19][20][21] However, it has not been applied to modify the properties of large strain BNT-based lead-free materials until recently. Several studies [22][23][24][25][26][27] have introduced ceramic/ceramic composite systems as a method to tune the electrical and electro-mechanical properties in lead-free ferroelectrics. Lee et al 22 have focused on the minimization of the actuating field of large strain BNT materials by forming a compositionally non-homogeneous phase structure (relaxor and ferroelectric) at the grain length scale.…”

“…The improved properties of the ceramic/ceramic composite material have been explained by a series capacitor model where polarisation coupling throughout the material reduces the required actuating fields. 22,26 Wada et al 23,25 have reported another type of compositionally non-homogeneous barium titanate-potassium niobate BaTiO 3 -KNbO 3 (BT-KN) ceramic. In this system, an artificial MPB has been created between single crystal particles of BT and an epitaxial shell of KN.…”

Structural study of heat-treated BaTiO₃–KNbO₃ nanocomposites with heteroepitaxial interface by synchrotron radiation powder diffraction

“…SEM and TEM observation showed that the BT and KN areas were well-separated, and the stoichiometric relationships Ba/Ti = 1 and K/Nb = 1 were kept in the BT and KN areas respectively even near the heteroepitaxial interface. 7)9) The large-field piezoelectric constant d 33 * of the nanocomposite ceramics has been obtained from the S-E curve for both assynthesized ceramics and heat-treated ones at 1000°C for 10 h. 8) The details of the KN formation on BT nanoparticles, the fabrication of the KN/BT nanocomposite ceramics, and the measurement of the S-E curve are described elsewhere. 7)9) The original ceramic plates were gently crushed to small ceramics pieces of approximately 0.1 mm in size which can be put into a glass capillary of 0.2 mm internal diameter.…”

“…7)9) The large-field piezoelectric constant d 33 * of the nanocomposite ceramics has been obtained from the S-E curve for both assynthesized ceramics and heat-treated ones at 1000°C for 10 h. 8) The details of the KN formation on BT nanoparticles, the fabrication of the KN/BT nanocomposite ceramics, and the measurement of the S-E curve are described elsewhere. 7)9) The original ceramic plates were gently crushed to small ceramics pieces of approximately 0.1 mm in size which can be put into a glass capillary of 0.2 mm internal diameter. High-energy SR powder diffraction patterns at 300 K were recorded on an imaging plate of the large DebyeScherrer camera installed at BL02B2 in SPring-8.…”

Fabrication of Ferroelectric Ceramics with Multi-Layered Structure by Solvothermal Solidification Method for Introduction of Internal Electric Field

“…The multi-layered ceramics is frequently fabricated by a tape casting method and a subsequent sintering process. However, since such KN-BT multi-layered ceramics is difficult to be fabricated without forming solid solution by the sintering process, we employed a solvothermal solidification method to fabricate ceramics at a low temperature below 250 o C. We have reported a series of studies on fabrication of the KN/BT nanocomplex ceramics with epitaxial KN/BT interface by using the solvothermal solidification method [10][11][12][13][14][15]. In this study, the green sheets containing Nb 2 O 5 , and BT or KN nanoparticles were prepared by the tape casting and were stacked to construct the multi-layered structure.…”