Liu Zhenhua ¹, Yi Shefeng ¹, Meng Quanyin ², Ji Shuai ²

(1. Jinduicheng Molybdenum Industry Co., Ltd., Xi'an 710077, Shaanxi, China; 2. School of Materials Science and Engineering, Xi'an Shiyou University, Xi'an 710065, Shaanxi, China)

Extended abstract:

[Significance] With the continuous advancement of microelectronic integration, new energy technology and high-temperature extreme environment engineering, functional ceramic materials with high stability, tunable electronic properties and multi-field adaptability have become indispensable core materials for modern advanced manufacturing and emerging energy industries. As an important branch of functional ceramic materials, molybdenum-based ceramic materials integrate excellent high-temperature thermal stability, outstanding mechanical strength, adjustable band gap structure, efficient electrocatalytic activity and promising biological compatibility, showing far more comprehensive performance advantages than many traditional metal and ceramic materials. Benefiting from these unique physicochemical characteristics, molybdenum-based ceramics have been widely applied in multiple key strategic fields, including new energy storage devices, high-sensitivity optoelectronic detection systems, industrial electrocatalytic reaction equipment and high-precision biological sensing platforms. In recent years, driven by the iterative upgrading of miniaturized, high-efficiency and long-service-life functional devices, molybdenum-based ceramics have gradually evolved into the key research object and cutting-edge hotspot of high-temperature resistant and micro-nano functional materials worldwide. Nevertheless, mainstream molybdenum-based ceramic systems represented by molybdenum boride, molybdenum trioxide and molybdenum disulfide differ greatly in crystal structure, intrinsic physical properties and application scenarios. In the current research field, most studies focus on the performance optimization of a single material system or a single preparation process, while there is a lack of horizontal systematic comparison and comprehensive induction of the structural characteristics, process advantages and technical defects of various molybdenum-based ceramic materials. In addition, the restrictive mechanisms of key bottlenecks, such as process scaling difficulties, structural defect evolution and performance attenuation, have not been fully summarized and examined. Therefore, this paper was aimed to comprehensively sort out the phase system, mainstream preparation processes, functional application characteristics and existing key technical challenges of typical molybdenum-based ceramic materials. The in-depth review and summary of the current research status and existing problems can effectively fill the gaps in the systematic research of molybdenum-based ceramic composite systems, which is of important theoretical guiding significance and practical engineering value for promoting the precise performance regulation, low-cost large-scale preparation and industrial popularization application of high-performance molybdenum-based ceramic functional materials.

[Progress] Crystal structure characteristics, mainstream preparation technologies and diversified application scenarios of three typical molybdenum-based ceramic materials, namely molybdenum boride, molybdenum trioxide (MoO₃) and molybdenum disulfide (MoS₂), are summarized in this paper. Meanwhile, a detailed horizontal comparison is conducted on the technical advantages, inherent limitations, preparation cost and applicable experimental conditions of several mainstream synthetic routes widely used in current research, including high-temperature and high-pressure synthesis, selective etching, hydrothermal method, chemical vapor deposition (CVD) and physical vapor deposition (PVD). On this basis, the key technical bottlenecks that restrict the performance improvement, structural optimization and large-scale industrialization of each molybdenum-based ceramic material system are elaborated comprehensively. For MBene materials, the selective etching process of aluminum layers is not mature and stable at this stage, which easily causes structural damage and uneven material quality, resulting in great difficulties in high-quality and large-scale batch production. At the same time, the current research on MBene performance is overly dependent on theoretical simulation and computational analysis, while systematic and sufficient experimental verification of its actual service performance and structural stability under complex working conditions is seriously lacking. For MoO₃ materials, the microscopic formation mechanism and dynamic real-time evolution law of internal oxygen vacancies have not been completely clarified. The existing conventional material characterization technologies cannot accurately distinguish and identify bulk-phase defects and surface defects of MoO₃. Moreover, high-concentration oxygen vacancies generated in the preparation process are easy to cause irreversible lattice distortion, which further leads to low color response rate and poor cyclic stability of the material, limiting its application in high-precision optoelectronic devices. For MoS₂ materials, its intrinsic carrier mobility and band gap regulation performance are still significantly inferior to traditional silicon-based semiconductor materials. In the preparation of micro-nano small-size devices, MoS₂ is prone to various electrical performance defects and strain structural defects. In addition, the ubiquitous interlayer lattice mismatch problem and potential nanosheet biotoxicity risks greatly restrict its further popularization and application in high-precision microelectronic devices and high-sensitivity biological sensing fields.

[Conclusions and prospects] The core technical problems existing in structural design optimization, industrial preparation process and multi-dimensional performance regulation of three typical molybdenum-based ceramic material systems are concluded, while targeted feasible optimization ideas and future development directions aiming at the above-mentioned key technical bottlenecks are put forward. In view of the common problems of immature preparation technology, unclear defect evolution mechanism and widespread performance deficiencies in current molybdenum-based ceramic research, future core research directions should be focused on optimization and innovative improvement of etching and synthesis processes, in-depth exploration of the generation and dynamic evolution mechanism of internal defects in materials, and independent research and development of high-precision in-situ real-time characterization technologies. Furthermore, the construction of composite heterogeneous structures and the implementation of precise defect engineering are proven to be effective technical means to break through the inherent performance limitations of existing single molybdenum-based ceramic materials. With this review, the latest research progress, technical difficulties and application limitations of typical molybdenum-based ceramic systems were sorted out, while the corresponding solution strategies were systematically summarized. The outcomes can be used as reliable theoretical references and technical guidance for the subsequent in-depth research on defect engineering regulation, heterogeneous structure construction and innovative application of in-situ characterization technology, for the development and industrialization of high-performance and multi-functional molybdenum-based ceramic materials.

Key words: molybdenum borides; MoO₃; MoS₂; selective etching; oxygen vacancies