Influence of Ni2+ Doping on Crystallization Behavior and Magnetic Properties of Gehlenite-Based Calcium Aluminosilicate Glasses

Abstract

Studying glasses with gehlenite (Ca₂Al₂SiO₇) composition is highly attractive because they serve as an excellent, highly stable matrix for doping with luminescent or transition metal ions. They are actively studied for modern optoelectronics and biomedical applications, including LEDs and photonics; magnetic tuning; hyperthermia and cancer treatment; and high-temperature stability. In this study, the influence of Ni²⁺ doping on crystallization behavior and magnetic properties of gehlenite-based calcium aluminosilicate glasses was studied. The glasses with a gehlenite composition were prepared with different Ni²⁺ contents (0.1, 1.0, and 3.0 mol%). The glasses were prepared by conventional melt quenching. The prepared system was studied using X-ray diffraction analysis, differential thermal analysis (DTA), and a SQUID magnetometer. X-ray diffraction analysis confirmed the amorphous nature of all prepared systems. In the DTA curves of all samples, one exothermic effect was observed with a maximum in the temperature interval (1220–1320 K), which can be attributed to the crystallization of gehlenite. The maximum temperature of the crystallization peak decreased with increasing Ni²⁺ content in the glasses, indicating an increasing tendency to crystallize and lower thermal stability of doped glasses. The magnetic properties of glasses changed as the Ni²⁺ concentration increased, indicating the incorporation of Ni²⁺ ions into the glass matrix. Magnetization versus external magnetic field dependence at 300 K indicated that the addition of Ni²⁺ significantly influenced the magnetic properties of CAS glasses. First, with increasing Ni²⁺ content, the influence of the diamagnetic component decreases, and conversely, the proportion of the paramagnetic component increases. At 2 K, only the paramagnetic component of the magnetization is present; however, the influence of this component increases with increasing Ni²⁺ addition. Furthermore, the effect of crystallization on the magnetic properties of Ni-doped CAS glasses was investigated. The results will be used to shape and further process CAS glasses for magneto-optical applications.