Key Takeaways & Executive Findings
- •• Three high-purity calcium vanadates (CaV2O6, Ca2V2O7, Ca3V2O8) were synthesized and characterized as indirect band gap semiconductors with band gaps of 2.5–3.4 eV. • Standard DFT calculations accurately describe lattice parameters and band gaps, making them sufficient for these vanadates without the need for DFT+U corrections. • All three compounds exhibit significant photo- and electro-luminescence in the visible spectrum, indicating potential for phosphor and optoelectronic applications. • CaV2O6 shows a remarkable 10-fold luminescence enhancement under a modest pressure of 0.88 GPa, highlighting its promise for pressure-tunable optical devices.
Abstract
Metal vanadates garner significant interest because of their exceptional potential for use in diverse practical applications, which stems from their unique framework structures, bond strength heterogeneities, and strong O2−–V5+ charge-transfer bands. However, their optoelectronic properties have not yet been sufficiently explored. In this study, we synthesized three high-purity calcium vanadate compounds (CaV2O6, Ca2V2O7, and Ca3V2O8) and comprehensively investigated their optoelectronic properties via first-principles calculations and experimental characterizations. CaV2O6, Ca2V2O7, and Ca3V2O8 are indirect band gap semiconductors with band gaps of 2.5–3.4 eV. A comparative analysis between density functional theory (DFT) and DFT + U (local Coulomb interaction, U) calculations revealed that standard DFT was sufficient to accurately describe the lattice parameters and band gaps of these vanadates. Further luminescence studies revealed significant photo- and electro-luminescence properties within the visible light spectrum. Notably, the luminescence intensity of CaV2O6 exhibited a remarkable 10-fold enhancement under a modest pressure of only 0.88 GPa, underscoring its exceptional potential for use in pressure-tunable optical applications. These findings provide deeper insight into the electronic structures and optical behaviors of vanadates and highlight their potential as strong candidates for application in phosphor materials and optoelectronic devices.
1. Introduction
As industrialization accelerates, the global demands for sustainable energy and technology based on green materials are increasing [1–5]. Vanadium-based compounds, which are known for their diverse valence states and rich crystal structures, have become focal points in developing novel materials because of their wide ranges of potential applications [6–7]. These versatile oxidation states and complex structures render vanadium highly valuable for use in optical, electronic, and catalytic materials, with promise for application in fields such as light-emitting diodes, energy storage systems, superconductivity, and industrial catalysts. Additionally, the mechanical stabilities and high-temperature resistances of vanadium-based materials render them essential components in extreme environments and aerospace applications. These characteristics highlight the considerable importance and research potential of vanadium in modern technologies. China possesses abundant vanadium resources and places a high priority on their comprehensive development and utilization, accelerating the research and development of vanadium-based products, which is crucial in enhancing the efficient use of these resources [8–9].
Among vanadium-based materials, vanadate compounds, which are inorganic compounds containing vanadate ions, are particularly representative [10–13]. Vanadium, which is a transition metal with multiple oxidation states, forms covalent bonds with the oxygen atoms within the structures of vanadates, resulting in the formation of vanadyl polyhedra. These polyhedra can be combined in various manners via corner- or edge-sharing to form 1D, 2D, or 3D structures. The diversity and structural complexities of vanadates endow them with excellent physicochemical properties, indicating their significant potential for use in numerous applications, e.g., batteries [14–18], catalysts [19–20], optical devices [21–22], sensors [23–24], and thermoelectric materials [25–26]. Therefore, vanadate materials should be critical in advancing sustainable energy technologies and developing advanced materials.
Among the various vanadate materials, calcium vanadates (CaV2O6, Ca2V2O7, Ca3V2O8, and Ca4V2O9) [27–28] represent a significant subclass of metal vanadates characterized by their unique layered structures [29–32]. These materials exhibit remarkable chemical stabilities and photoluminescence (PL) and microwave dielectric properties. Recently, the distinct structural features of calcium vanadates attracted considerable research interest, positioning them as promising candidates for applications in optoelectronics and phosphors.
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Xin Jin, Xianyong Ding, Guishang Pei, Shuaiqi Li, Xing’an Dong, Xiaolong Yang, Rui Wang, Peng Yu, Xuewei Lü (2025). Exploring the optoelectronic properties of calcium vanadate semiconductors: A combined experimental and DFT study. Int. Journal of Minerals, Metallurgy and Materials (矿物冶金与材料学报). https://doi.org/10.1007/s12613-025-3095-9
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Frequently Asked Questions
What are the band gaps of the calcium vanadates studied?
The calcium vanadates CaV2O6, Ca2V2O7, and Ca3V2O8 are indirect band gap semiconductors with band gaps ranging from 2.5 to 3.4 eV.
How does pressure affect the luminescence of CaV2O6?
Under a modest pressure of only 0.88 GPa, the luminescence intensity of CaV2O6 exhibits a remarkable 10-fold enhancement, indicating its potential for pressure-tunable optical applications.
What methods were used to investigate the optoelectronic properties?
The study combined experimental characterizations with first-principles calculations, including density functional theory (DFT) and DFT+U, to analyze the electronic structures and optical behaviors of the calcium vanadates.
Why are calcium vanadates considered promising for optoelectronic applications?
Calcium vanadates exhibit significant photo- and electro-luminescence in the visible spectrum, along with good chemical stability and unique layered structures, making them strong candidates for phosphor materials and optoelectronic devices.
What is the significance of the DFT calculations in this study?
The comparative analysis between standard DFT and DFT+U revealed that standard DFT is sufficient to accurately describe the lattice parameters and band gaps of these vanadates, simplifying future computational studies of similar materials.
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