Reviewed by Danielle Ellis, B.Sc.Sep 19 2024
Researchers from Nagoya University have created four- and five-layered forms of perovskite, a significant electrical material. Upon examining the ferroelectricity mechanism within the material, the researchers discovered that it serves a distinct purpose: the material alternates between its ferroelectric processes based on whether the number of layers is even or odd. The study was published in the Journal of the American Chemical Society.
Scientists anticipate that the development of new electronic devices will be substantially expanded by these different properties.
Perovskites are a class of materials consisting of calcium titanium oxides with the same crystal structure. They are commonly used in electronic devices due to a characteristic known as ferroelectricity. Thanks to ferroelectricity, electric polarization can be controlled and reversed by an external electric field. This feature makes perovskites valuable for electronic devices like memory, capacitors, actuators, and sensors, which rely on on and off states.
Researchers are developing new compositions, topologies, and lead-free ferroelectrics to enhance the goods' usefulness and lessen their environmental impact. Perovskites, particularly layered perovskites of the Dion-Jacobson (DJ) type, are emerging as a significant class of materials in this field of study.
Due to their layered octahedral structure, DJ-type perovskites contain asymmetrical layers that give them ferroelectric characteristics. When an external field is applied, the positive and negative ions shift, leading to size mismatches that cause the octahedra to tilt and rotate. This is the source of the ferroelectric characteristics. This tilting reduces the material's symmetry, which enhances ferroelectric behavior.
Thermodynamic stability decreases with increasing perovskite layer thickness. Researchers view layered perovskites as untapped materials, according to Minoru Osada of Nagoya University's Institute of Materials and Systems for Sustainability (IMaSS).
To overcome this, the study team created a brand-new synthesis technique called the template synthesis method. This method mixes perovskite layers one at a time and aligns their octahedrons like bricks to create multilayer structures.
In the template synthesis method, the number of layers can be increased by one layer by using a three-layer system as the starting material and reacting it with SrTiO3. By repeating the reaction, the number of perovskite layers can be digitally controlled according to the number of reactions, allowing the synthesis of a multilayer structure. By applying the template synthesis method, we synthesized four- and five-layered perovskites for the first time.
Minoru Osada, Institute of Materials and Systems, Nagoya University
Fascinatingly, when testing the material, they discovered that its behavior varied according to the number of layers, displaying distinct dielectric constants and Curie temperatures.
We found that the number of layers plays an important role in this system and that it has a unique function to switch to the conventional direct ferroelectricity model when the number of layers is odd and to the new indirect ferroelectricity model when the number is even.
Minoru Osada, Institute of Materials and Systems, Nagoya University
Their method offers a fresh chance to go beyond the thermodynamically stable phases in the range of ferroelectric materials. This accomplishment is anticipated to significantly broaden the material search space in the field of ferroelectrics research and development. It will also offer crucial guidance for the creation of novel materials and functions that are challenging to attain with currently available materials and methods.
Journal Reference:
Morita, S., et al. (2024) Atomic Layer Engineering of Ferroelectricity in Dion-Jacobson Perovskites. Journal of the American Chemical Society. doi.org/10.1021/jacs.4c09214.
Source:
Nagoya University