Feasible Synthesis of Rare Earth-Free Zinc Silicate-Based Ceramics
NECIB J. 1, ROJAS-HERNANDEZ R. 1, RUBIO-MARCOS F. 2, HUSSAINOVA I. 1, FERNANDEZ J. 2, FELDBACH E. 3
1 Department of Mechanical and Industrial Engineering, Tallinn University of Technology, Ehitajate 5, 19180 , Tallinn, Estonia; 2 Electroceramic Department, Instituto de Cerámica y Vidrio, CSIC, Kelsen 5, 28049, Madrid, Spain; 3 Institute of Physics, University of Tartu, W. Ostwald Str 1, 50411, Tartu, Estonia
ABSTRACT
Zinc silicate (Zn2SiO4) has gained significant attention due to its unique physical, electrical, and luminescent properties [1], making it attractive for various applications such as UV detectors, gas sensors, adsorption of toxic ions from water, and optoelectronic devices [2,3]. Zn2SiO4 is frequently utilized as a host for rare earth and transition metal ions, which emit light in the ultraviolet, visible, or infrared ranges [4]. Despite its widespread use, the emission mechanism of undoped Zn2SiO4 has remained poorly understood due to the lack of research on this subject. In addition, the scarcity of natural resources has led to an increased interest in developing alternative materials to replace the commonly used rare earth dopants in phosphors. This study aims to investigate the potential of undoped Zn2SiO4 as a non-rare earth alternative phosphor by gaining a deeper understanding of its emission mechanism.
The current study focuses on synthesizing rare-earth-free Zn2SiO4 powders through the sol-gel method. The resulting powders were then annealed at temperatures ranging from 600 to 1300 °C, and both polymorphs of zinc silicate, α-Zn2SiO4 and β-Zn2SiO4, were observed. To gain a deeper understanding of the phase transitions and reaction mechanisms, in situ high-temperature study X-ray diffraction was used to monitor the process. The results showed that the metastable β-Zn2SiO4 phase was stabilized at 750 to 850 °C, and the formation of α-Zn2SiO4 was detected at 950 °C. The crystal structure was further analyzed using Rietveld refinement and confirmed through Raman spectroscopy. Notably, the annealing process resulted in a transformation of the α-Zn2SiO4 phase from the orthorhombic structure of β-Zn2SiO4 to a rhombohedral structure.
Luminescence examination was performed using cathodoluminescence measurements conducted at cryogenic and room temperatures. The measurements provided an evidence of emission in the UV to the Visible range. This work provides new insights into the optimization of rare-earth-free Zn2SiO4 for various applications, and further highlights the importance of understanding the emission mechanism of this promising material. These findings contribute to the ongoing efforts to develop sustainable and environmentally friendly alternatives to rare earth phosphors.
References:
[1] C. Feldmann, et al. Inorganic Luminescent Materials: 100 Years of Research and Application. Advanced Functional Materials, 13, 511-516 (2003).
[2] D.K. Bharti, et al. Synthesis and Characterization of Highly Crystalline Bi-Functional Mn-Doped Zn2SiO4 Nanostructures by Low-Cost Sol–Gel Process. Nanomaterials, 13, 538 (2023).
[3] S.A.A. Wahab, et al. Blue emission: Optical properties of Co2+ doping towards Zn2SiO4 glass-ceramics, Optik, 274, 170528 (2023).
[4] V. Lojpur, et al. Luminescence thermometry with Zn2SiO4: Mn2+ powder. Appl Phys Lett, 103, 1-3 (2013).
