R.V.S.S.N. Ravikumar

Spectroscopic studies of transition metal doped sodium phosphate glasses

Optical absorption and EPR spectra of Co2+ and Ni2+ doped sodium phosphate glasses have been investigated. Crystal field parameters and g values are determined. For Co2+ doped glass Dq=890, B=700, C=4125 cm−1 and g values of 4.23 and 2.04 at 20 K, for Ni2+ doped glass Dq=890, B=770, C=3700 cm−1 and a g value of 2.28 at room temperature were found. Correlating the optical and electron paramagnetic resonance data suggests the bonding between transition metal ions and ligands as ionic in nature.

EPR and optical studies on transition metal doped LiRbB4O7 glasses

Abstract Electron paramagnetic resonance and optical investigations of copper and chromium doped LiRbB 4 O 7 glasses are carried out. From the results and discussions, it is predicted that both the transition metal ions exhibit octahedral environment. In the case of Cr 3+ , the site symmetry is near octahedral, whereas in the case of Cu 2+ , it is tetragonally distorted octahedral environment. Crystal field, spin-Hamiltonian and bonding parameters are evaluated. The bonding parameters are suggesting ionic.

Site symmetry of Mn(II) and Co(II) in zinc phosphate glass

Abstract Optical absorption and EPR spectra of Mn(II) and Co(II) doped zinc phosphate glasses have been investigated. Crystal filed parameters and g values are determined. For Mn(II) doped glass the values are Dq=850, B=850, C=2975 cm −1 and g values are around 2 at room temperature (RT). For Co(II) doped glass, Dq=890, B=700, C=4100 cm −1 and g=4.45 and 2.06 at liquid nitrogen temperature. The optical and EPR data has been correlated.

Spectroscopic studies of copper-doped ARbB4O7 (A=Na, K) glasses

Abstract EPR and optical absorption investigations are carried out at room temperature on copper-doped ARbB4O7 (A=Na, K) glasses. The results indicate that the copper ions (Cu2+) enter the glass matrix into a tetragonally elongated octahedral site. Crystal field and spin-Hamiltonian parameters are evaluated. The bonding parameters indicate that bonding between the metal ions and ligands is partially covalent.

Orthorhombic Site Symmetry of Cr3+ in ZnNH4PO4 6H2O Crystals

Spectroscopic investigations of Cr 3+ doped ZAPH are carried out. From the nature of optical absorption bands and their splittings at the liquid nitrogen temperature, the site symmetry of the Cr 3+ in ZAPH is attributed to orthorhombic distortion.

Optical and EPR investigations on smithsonite minerals

Optical and EPR investigations have been made on two smithsonite (ZnCO3) minerals, one originating from the USA and the other from the UK. The optical spectra reveal the existence of Cu(II) as impurity in both the samples; and site symmetry for Cu(II) is confirmed to be tetragonally distorted octahedral. The intensity of absorption bands observed in the region 600–1200 nm in the USA sample is much stronger indicating that the impurity of Cu(II) is more in the USA sample than that in the UK sample. From EPR spectra the axial g values are determined to be g ‖ = 2.337 and g ⊥ = 2.087, which are compatible with the distorted octahedral symmetry. In addition, Mn(II) impurity is also detected in the EPR spectra of both the samples.

Spectral Studies on VO2+ doped MPPH Crystals

Magnesium Potassium Phosphate Hexahydrate (MPPH), is analogous to the bio-mineral struvite. Vanadyl doped MPPH crystals are grown by slow evaporation technique. EPR and optical absorption studies are carried out at room and liquid nitrogen temperatures. Spin-Hamiltonian, crystal field and bonding parameters are evaluated.

Spectral investigations on melanterite mineral from France

EPR, Optical and IR spectral studies on a naturally occurring mineral melanterite are carried out at room temperature. EPR studies indicate the presence of Cu(II) ion in tetragonally distorted octahedral site and hyperfine lines could not be resolved due to higher concentration of the paramagnetic impurity in the mineral. Optical absorption spectrum is a characteristic of Fe(II) and Cu(II) ions. Crystal field parameters are evaluated. IR spectrum confirms the presence of water and sulphate ions.

X-ray powder diffraction, DTA and vibrational studies of CdNH4PO4.6H2O crystals

Cadmium Ammonium Phosphate Hexahydrate (CAPH) is analogous to naturally occurring struvite. CAPH crystals are grown by slow evaporation technique. These crystals are characterised by X-ray, TG-DTA and Infra-red studies. Powder X-ray pattern indicates the orthorhombic crystal structure analogous to struvite. TG-DTA analysis suggests loss of water of hydration (6H 2 O) between 113 and 391°C. Later the substance melts and only Cd remains around 780°C. Infra Red spectrum is characteristic of H 2 O, PO 4 3- and NH 4 + radicals.

Cu(II), Mn(II) in tetragonal site in chrysocolla

Chrysocolla samples from two regions are studied spectroscopically to ascertain the site symmetries of the transition metal ions present in them. The results indicate the tetragonal site symmetry for Cu(II) and Mn(II). The crystal field and spin Hamiltonian parameters are evaluated.