Controlling Phase Purity and Texture of K0.5Na0.5NbO3 Thin Films by Aqueous Chemical Solution Deposition

Abstract

Aqueous chemical solution deposition (CSD) of lead-free ferroelectric K0.5Na0.5NbO3 (KNN) thin films has a great potential for cost-effective and environmentally friendly components in microelectronics. Phase purity of KNN is, however, a persistent challenge due to the volatility of alkali metal oxides, usually countered by using excess alkali metals in the precursor solutions. Here, we report on the development of two different aqueous precursor solutions for CSD of KNN films, and we demonstrate that the decomposition process during thermal processing of the films is of detrimental importance for promoting nucleation of KNN and suppressing the formation of secondary phases. Based on thermal analysis, X-ray diffraction and IR spectroscopy of films as well as powders prepared from the solutions, it was revealed that the decomposition temperature can be controlled by chemistry resulting in phase pure KNN films. A columnar microstructure with out-of-plane texturing was observed in the phase pure KNN films, demonstrating that the microstructure is directly coupled to the thermal processing of the films.

In Vitro Biocompatibility of Piezoelectric K0.5Na0.5NbO3 Thin Films on Platinized Silicon Substrates

“…GIXRD patterns of the KNN and KNN-CaTiO 3 thin films are presented in Figure S1 in the Supporting Information. All of the Bragg reflections can be assigned to monoclinic K 0.5 Na 0.5 NbO 3 and the substrate, confirming that single phase KNN was deposited on SiPt substrates using the aqueous CSD route. , …”

“…All of the Bragg reflections can be assigned to monoclinic K 0.5 Na 0.5 NbO 3 31 and the substrate, confirming that single phase KNN was deposited on SiPt substrates using the aqueous CSD route. 25,26 The surface morphologies of the glass coverslips, SiPt substrates, and the KNN and KNN-CaTiO 3 thin films are presented in Figure 2. The topography observed on the two KNN samples originates from the grain structure of the KNN films.…”

“…Undoped KNN (K 0.5 Na 0.5 NbO 3 ) and 0.5 mol % CaTiO 3 -doped KNN films (K 0.4975 Na 0.4975 Ca 0.005 Nb 0.995 Ti 0.005 O 3 , KNN-CaTiO 3 ) were prepared using aqueous precursor solutions described elsewhere. , The solutions were prepared by precipitating niobic acid from an aqueous solution of NH 4 NbO­(C 2 O 4 ) 2 · x H 2 O (99.99%, Sigma-Aldrich, St. Louis, MO, U.S.A.) using ammonia solution (25 wt %, VWR Chemicals, Radnor, PA, U.S.A.). The niobic acid precipitate was dissolved in deionized water with DL-malic acid (99%, Sigma-Aldrich) in a molar ratio of 1:2.…”

“…Here, we report on in vitro biocompatibility of KNN thin films on platinized silicon (SiPt) substrates. Undoped and 0.5 mol % CaTiO 3 -doped KNN films were synthesized by aqueous chemical solution deposition (CSD) on SiPt substrates based on a previously reported processing route. , The biocompatibility of these films was assessed through proliferation, morphology, and viability assays using human 161BR fibroblast cells and rat (glial) Schwann cells. To deconvolute the biological effects from the KNN films and the substrate, SiPt substrates with no deposited film were also tested.…”

Mechanisms for texture in BaTiO3 thin films from aqueous chemical solution deposition

“…Ba is depleted from the perovskite phase by local high CO 2 pressure from the oxycarbonate decomposition, leading to areas with Badeficient Ba y TiO 2+y phases and BaCO 3 (aragonite type). Cation segregation due to formation of secondary phases and alkali volatility has also been observed in KNN thin films from CSD, with similar precursor chemistries [31,33]. A thorough understanding and control over the decomposition reactions and the transformation pathway for the precursors are therefore of outmost importance for producing high quality multilayer thin films with high degree of texture from CSD.…”