Exploring the Milarite mineral, Na2Mg5-xMxSi12O30 (M = Co2+, Zn2+, Ni2+, Cu2+), Na2Mg2.5Ca0.5-xLnxZn2Si12O30 (Ln = Eu3+, Tm3+, Tb3+) towards new colored compounds, white - light emission, and Oxygen evolution reaction (OER)

New transition metal substituted milarite silicates of the general formula A2B2C[T(2)3T(1)12O30], were prepared by conventional solid state technique and their structures determined by powder X-ray diffraction (PXRD) methods. Raman spectroscopic studies indicated expected Raman bands. The oxidation states of the transition elements were confirmed by XPS studies. The optical absorption bands were rationalized based on the ligand-centered emission and allowed d-d transitions. The white compounds exhibited a good deep UV Cut off values, suggesting the possible use as optical filters. The white compounds also showed good near-infrared (NIR) reflectivity that is comparable to the commercial TiO2. The rare earth substituted compounds, Na2Mg2.5Ca0.5-xLnxZn2Si12O30, exhibited intense red (Eu3+), green (Tb3+) and blue (Tm3+) emissions. An optimal composition having all the three lanthanide ion substitutions resulted in white light emissions in Na2Mg2.5Ca0.48Tm0.01Tb0.02Eu0.01Zn2Si12O30. The presence of Co2+ in Na2Mg3Co2Si12O30 compound facilitated the study of oxygen evolution reaction (OER) with good values that are comparable to RuO2. The white compounds have reasonably good dielectric constant values with low dielectric loss, which indicates possible use in communication devices. The milarite based compounds exhibited considerable potentials towards new colored compounds, white light emission and OER properties. The present study suggests that it is profitable exploring mineral structures towards new and known material properties