Fabrication of undoped and (Mn,Ce,Eu,Tb) doped nickel borate nanosized ceramic powders

In this work, the fabrication of undoped and doped nanosized nickel orthoborate ceramic powders was carried out by high temperature solid state synthesis method. The nickel orthoborates were prepared in two compositions with various dopant concentrations: manganese (II) doped, Ni3(BO3)2: Mn2+ and 0.01 mol manganese (II) combined with rare earth metal, Ni3(BO3)2: 0.01Mn2+RE3+ (RE = Ce, Eu, and Tb). All the synthesized materials were characterized using X-ray Diffraction (XRD), Infrared Spectroscopy (FTIR), Diffuse Reflectance Spectroscopy (DRS) and Thermogravimetric/Differential Thermal Analysis (TG/DTA) to determine their structural, chemical, optical and thermal properties, respectively. XRD Data analysis indicated that highly crystalline Ni3(BO3)2:Mn2+ has an optimal manganese concentration of 0.01 mol, with no changes in crystal structure upon doping. Additionally, FTIR techniques revealed that all the characteristic bands of orthoborates were observed between 2000–500 cm− 1. DRS studies of Ni3(BO3)2: 0.01Mn2+xRE3+ revealed two dominant reflectance bands: at around 350-550 nm and 650-850 nm. Europium was found to be the most suitable co-activator, with an optimum concentration of 0.010 mol. Moreover, the reflectance bands shifted towards shorter wavelengths, moving from visible region to NIR-UV due to contributions from cerium, europium, and terbium. Furthermore, the pure Ni3(BO3)2 compound has a forbidden energy value of Eg = 3.148 eV. For Ni3(BO3)2: Mn2+, the values were found to range from 3.330-3.170 eV. In Ni3(BO3)2: 0.010Mn2+ compounds doped with rare earth metals, the values ranged from 3.16-3.14 eV (cerium-doped), 3.32-3.36 eV (europium-doped), and 3.32-3.34 eV (terbium-doped). The TG/DTA analysis demonstrated an endothermic peak around 1380ºC for all samples.