Structure and magnetic properties of Ni- doped gehlenite glass microspheres

Abstract

The structural and magnetic properties of undoped and Ni-doped aluminate glass microspheres with gehlenite (Ca2Al2SiO7) composition and of their polycrystalline analogues were studied. The concentration of Ni was 0.0, 0.5 and 3.0 mol. %. Glass microspheres were prepared by combination of solid-state reaction and flame synthesis. The detailed examination of morphology of the glass microspheres of all prepared composition by scanning electron microscopy (SEM) revealed no features indicating presence of crystalline phases. X-ray powder diffraction (XRD) confirmed amorphous character of prepared Ni-doped gehlenite glass microspheres. In samples crystallized at 1273 K for 10 h, XRD revealed the presence of gehlenite as the main crystalline phase. Raman spectroscopy of crystallized samples also confirmed the presence of gehlenite. Raman spectra of as-prepared glass microspheres differed significantly from the spectra of their crystallized counterparts. These indicate the role of aluminum as a network-forming element. Magnetic properties of the Ni-doped gehlenite microspheres and of their polycrystalline analogues were measured by SQUID magnetometer. Properties of the measured samples showed a more complex magnetic behaviour. Diamagnetic, paramagnetic and ferromagnetic components can be observed depending on whether Ni-doping is used or not, as well as depending on temperature and applied magnetic field values, both for glass microspheres and crystalline samples.