engleski

Robust Macroscopic Polarization of Block Copolymer–Templated Mesoporous Perovskite‐Type Thin‐Film Ferroelectrics

Ferroelectrics play an important role in various applications, from electronics, to mechanics, optics, and biomedicine. Herein, we describe the preparation and characterization of a series of block copolymer-templated mesostructured (lead- free) oxide ferroelectrics. Distorted perovskite lithium niobate (LiNbO3), lithium tantalate (LiTaO3), and solid solution LiNbO3-LiTaO3 were produced as single-phase thin films of good quality by the dip-coating method using an evaporation-induced self-assembly process. After heating between 300-700 °C, they were investigated by a combination of microscopy, diffraction, X-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectrometry. Thermal treatment at ≥600 °C was required to initiate crystallization. Both the pore ordering and thermal stability increased significantly with increasing tantalum content. Ferroelectric testing through dynamic and remanent polarization experiments at ambient conditions confirmed the uniformity and purity of the LiNbO3 thin-film system. Results from positive-up and negative-down test measurements revealed a stable switching polarization of 2 μC cm–2, with a coercive field of 50 kV cm–1. Taken together, the lithium niobium and tantalum oxides prepared in this work are rare examples of sol-gel derived perovskite type materials with an ordered mesoporous morphology. Because of the spontaneous electrical polarization observed for LiNbO3, such block copolymer- templated thin films might pave the way for the development of a new class of three-dimensional nanocomposite ferroics.

sol-gel chemistry ; polymer templating ; lithium niobate ; lithium tantalate ; ferroelectricity

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