Synthesis of KCa₂Nb₃O₁₀ Crystals with Varying Grain Sizes and Their Nanosheet Monolayer Films As Seed Layers for PiezoMEMS Applications

Huiyu Yuan; Minh Nguyen; Tom Hammer; Gertjan Koster; Guus Rijnders; Johan E ten Elshof

doi:10.1021/acsami.5b09456

Synthesis of KCa₂Nb₃O₁₀ Crystals with Varying Grain Sizes and Their Nanosheet Monolayer Films As Seed Layers for PiezoMEMS Applications

ACS Appl Mater Interfaces. 2015 Dec 16;7(49):27473-8. doi: 10.1021/acsami.5b09456. Epub 2015 Dec 2.

Authors

Huiyu Yuan¹, Minh Nguyen^{1

2

3}, Tom Hammer¹, Gertjan Koster¹, Guus Rijnders¹, Johan E ten Elshof¹

Affiliations

¹ MESA+ Institute for Nanotechnology, University of Twente , P.O. Box 217, 7500 AE Enschede, The Netherlands.
² Solmates B.V. , Drienerlolaan 5, 7522NB Enschede, The Netherlands.
³ International Training Institute for Materials Science (ITIMS), Hanoi University of Science and Technology , Dai Co Viet 1, Hanoi, Vietnam.

PMID: 26583282
DOI: 10.1021/acsami.5b09456

Abstract

The layered perovskite-type niobate KCa2Nb3O10 and its derivatives show advantages in several fields, such as templated film growth and (photo)catalysis. Conventional synthesis routes generally yield crystal size smaller than 2 μm. We report a flux synthesis method to obtain KCa2Nb3O10 crystals with significantly larger sizes. By using different flux materials (K2SO4 and K2MoO4), crystals with average sizes of 8 and 20 μm, respectively, were obtained. The KCa2Nb3O10 crystals from K2SO4 and K2MoO4 assisted synthesis were protonated and exfoliated into monolayer nanosheets, and the optimal exfoliation conditions were determined. Using pulsed laser deposition, highly (001)-oriented piezoelectric stacks (SrRuO3/PbZr0.52Ti0.48O3/SrRuO3, SRO/PZT/SRO) were deposited onto Langmuir-Blodgett films of Ca2Nb3O10(-) (CNO) nanosheets with varying lateral nanosheet sizes on Si substrates. The resulting PZT thin films showed high crystallinity irrespective of nanosheet size. The small sized nanosheets yielded a high longitudinal piezoelectric coefficient d33 of 100 pm/V, while the larger sized sheets had a d33 of 72 pm/V. An enhanced transverse piezoelectric coefficient d31 of -107 pm/V, an important input parameter for the actuation of active structures in microelectromechanical systems (MEMS) devices, was obtained for PZT films grown on CNO nanosheets with large lateral size, while the corresponding value on small sized sheets was -96 pm/V.

Keywords: PZT thin films; exfoliation; flux synthesis; layered perovskite-type niobate; molten salt synthesis; monolayer nanosheets; piezoelectric properties; protonation.