Identification number: lzp-2024/1-0632
Type: Latvian Council of Science Fundamental and Applied Research project
Project duration: 01.01.2025.-31.12.2027.
Project Leader: Dr. Habil. phys., PhD. Smagul Karazhanov, Institute of Solid State Physics, University of Latvia
Total funding: 300 000 EUR
Project title: Innovative Thin Films of Rare-Earth Metal Oxyhydrides: Unlocking New Applications
Project aim:
The project aims to develop new materials based on oxyhydrides of high entropy rare earth metal elements. Distinct from the mixed anion oxyhydrides including a single cation and two types of anions, the new materials contain more than one type of cations and two anions. The oxyhydrides of the high entropy rare earth and transition metal elements are expected to possess more advanced photochromic performance than the single anion ones.
Expected scientific results:
In today's quest for materials that boast enhanced properties, cost-effectiveness, and environmental sustainability, the emergence of high-entropy rare-earth metal oxyhydrides (HEREMO) stands out as a promising game-changer. HEREMO, defined as solid solution materials with quasi-equimolar multicomponents, exhibits a unique structural characteristic - antisite disordering of atomic types within an ordered crystal. This structural peculiarity opens up intriguing avenues for exploration across a wide array of applications, ranging from smart windows to functional coatings, sensors, and catalysts. Review literature underscores the versatility of high-entropy materials, showcasing their efficacy in diverse energy-related applications. However, despite their promise, challenges persist, including a lack of comprehensive understanding, limited characterization techniques, and the need for advanced fabrication methods. This project focuses on the synthesis and characterization of HEREMO and its derivatives with the aim of unlocking new frontiers in materials science. Through a combination of experimental investigations and theoretical modeling, we seek to delve into the structural, electronic, and optical properties of HEREMO materials. By addressing key challenges and leveraging innovative approaches, our research aims to pave the way for transformative applications of HEREMO across diverse technological domains.
ON THE IMPLEMENTATION OF THE PROJECT (PERIOD 01.10.2025 – 31.12.2025)
During the reporting period, the magnetron sputtering system was prepared for the next stage of the research – the fabrication of mixed rare-earth metal oxyhydride thin films involving co-sputtering from three rare-earth targets.
From 16 to 17 December, the Master's student involved in the project, Emija Ļetko, participated in the RSD 2025 conference held in Manchester, United Kingdom. A poster presentation entitled “Magnetron sputtering of newly developed photochromic oxygen-containing lutetium hydride (LuHO) thin films” was presented, showcasing results obtained within this project. Within the framework of the conference, a short course on reactive magnetron sputtering was also attended. The knowledge gained during the course and conference will be applied in the further implementation of the project.
ON THE IMPLEMENTATION OF THE PROJECT (PERIOD 01.07.2025 – 30.09.2025)
During the reporting period, the fabrication of new rare-earth oxyhydride (REHO) thin films was continued, this time focusing on lutetium oxyhydride (LuHO). The obtained coatings exhibited significantly improved stability in ambient atmosphere compared with LaHO films. LuHO also demonstrated photochromic properties and a structure similar to YHO, thereby expanding the family of photochromic REHO materials. The influence of hydrogen flow and sputtering pressure on the film structure and optical properties was investigated.
From 25 to 29 August, the Master's student involved in the project, Emija Ļetko, participated in the conference and summer school “Advanced Materials and Technologies 2025”, held in Palanga, Lithuania. The project results were presented, and new knowledge in the field of materials science was gained, which will be beneficial for the further implementation of the project.
ON THE IMPLEMENTATION OF THE PROJECT (PERIOD 01.04.2025 – 30.06.2025)
During the corresponding time period, new thin films of lanthanum oxyhydride (LaHO) were fabricated. It was found that the obtained coatings are highly reactive toward ambient air, which leads to degredation within a few hours. To avoid undesirable degradation of the coatings, sample oxidation was performed in a controlled manner by introducing oxygen into the vacuum chamber, and the samples were additionally covered with protective layers (AlNx and Al2O3). Photochromic samples with a structure similar to that of yttrium oxyhydride (YHO) were obtained. The influence of oxidation time on the structure, morphology and optical properties was investigated. The preparation of a scientific manuscript on the obtained results was initiated.
ON THE IMPLEMENTATION OF THE PROJECT (PERIOD 01.01.2025. - 30.03.2025.)
During the reporting period, the multifunctional vacuum system SAF25/50 was prepared for the tasks of this project. The planned technology for the fabrication of HEREMO thin films is magnetron sputtering. The vacuum chamber was equipped with the necessary power supplies and a gas supply and control system for the process gases – argon and hydrogen. The chamber is connected to a hermetically sealed glovebox filled with inert gas, enabling the handling of samples before they come into contact with the atmosphere. This setup is required because HEREMO compounds are expected to be reactive with oxygen.
The first thin-film samples of rare-earth oxyhydrides were fabricated on glass substrates, and the process parameters ensuring a stable and reproducible deposition process were determined. Structural, compositional, and optical (including photochromic) property measurements are planned for these samples.
In addition, two students were trained to work with the SAF25/50 system, and they will participate in sample fabrication during the continuation of the project.
