We describe the synthesis, structure, optical, magnetic, and dielectric properties of Zn 3 B 2 O 6 and Co 3 B 2 O 6 systems with the detailed investigation of the structural transition along with the evolution of color. The compounds (Zn 3-x Co x )B 2 O 6 (0 � x � 3) were synthesised by high temperature solid-state reactions. Rietveld refinements of the powder X-ray diffraction (PXRD) patterns on (Zn 2.25 Co 0.75 )B 2 O 6 and (Co 2.25 Zn 0.75 )B 2 O 6 samples indicate uniform distribution of Zn and Co in their respective crystallographic sites. UV-Vis absorption spectra on the samples can be explained based on the electronic transitions of Co 2 + ions in tetrahedral and octahedral coordination. NIR reflectivity studies on Zn 3 B 2 O 6 was found to be better than that of TiO 2 , which suggests possible use of this compound for reflective coatings. The temperature dependent magnetic susceptibility studies indicate antiferromagnetic behaviour. The compounds exhibit low dielectric loss across the investigated frequencies.

Mixed-metal oxides, AM2C6Te3O18 (A = Pb, Sr; M = Mn, Cd; C = Ni, Co), have been synthesized employing traditional solid-state methods. The prepared compounds were characterized by powder X-ray diffraction (PXRD) and the structures refined by Rietveld analysis. The optical absorption studies of the compounds were carried out employing UV–vis spectroscopy and the observed transitions were assigned to the octahedral transition metal ions. Magnetic studies were carried out on PbCd2Co6Te3O18, SrCd2Co6Te3O18, and SrCd2Ni6Te3O18, which indicated that the compounds order antiferromagnetically around 10 K. Computational approaches were employed to fit the observed magnetic behavior.