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

Abstract

AbstractFerroelectrics play an important role in various applications, from electronics to mechanics, optics, and biomedicine. Here, the preparation of a series of block copolymer–templated mesostructured (lead‐free) oxide ferroelectrics is described. Distorted perovskite LiNbO3, LiTaO3, and solid solution LiNbO3–LiTaO3 are produced as single‐phase thin films of good quality by the dip‐coating method using an evaporation‐induced self‐assembly process. They are investigated by a combination of electron microscopy, X‐ray diffraction and scattering, X‐ray photoelectron spectroscopy, and time‐of‐flight secondary ion mass spectrometry. Thermal treatment at ≥600 °C is required to initiate crystallization. Both the pore ordering and thermal stability increase with increasing tantalum content. Ferroelectric testing through dynamic and remanent polarization experiments at ambient conditions confirm the uniformity and purity of the LiNbO3 thin‐film system. Results from positive‐up and negative‐down test measurements reveal 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 the 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 3D nanocomposite ferroics.