Ch. Linga Raju

Spectroscopic and radiative properties of Sm3+ ions in zinc borophosphate glasses

The paper reports on the preparation and characterization of Sm3+ doped zinc borophosphate (ZBP) glasses. The density was measured and the corresponding molar volume was evaluated. The present glass system was investigated by the XRD, optical absorption, photoluminescence, decay curves and FTIR analysis. The Judd–Ofelt theory has been used to evaluate the JO intensity parameters (Ω2,4,6) and calculated oscillator strengths (ƒcal). Using JO intensity parameters, various radiative parameters such as transition probability (AR), radiative lifetime (τR), measured lifetime (τm), calculated branching ratios (βR), measured branching ratios (βm) have been calculated for the excited 4G5/2 level. The nature of the decay curves of 4G5/2 level for different Sm3+ ion concentration in all ZBP glasses has been analyzed and the lifetimes are noticed to decrease with increase of concentration.

Coordination and ion–ion interactions of chromium centers in alkaline earth zinc borate glasses probed by electron paramagnetic resonance and optical spectroscopy

Electron paramagnetic resonance (EPR), optical absorption and FT-IR studies have been carried out on chromium ions incorporated in alkaline earth zinc borate glasses. The EPR spectra exhibit two resonance signals with effective g values at g ≈ 1.99 and ≈1.97. The resonance signal at g ≈ 1.99 is attributed to the contribution from both the exchange coupled Cr3+–Cr3+ ion pairs and the isolated Cr3+ ions and the resonance signal at g ≈ 1.97 is due to Cr5+ ions. The paramagnetic susceptibility (χ) was calculated from the EPR data at various (123–303 K) temperatures and the Curie temperature (θp) was calculated from the 1/χ–T graph. The optical absorption spectra exhibit three bands at ~360 nm, ~440 nm and a broad band at ~615 nm characteristic of Cr3+ ions in an octahedral symmetry. From the observed band positions, the crystal-field splitting parameter Dq and the Racah parameters (B and C) have been evaluated. From the ultraviolet edges, the optical band gap energies (Eopt) and Urbach energy (ΔE) are calculated. The theoretical optical basicity (Λth) of these glasses has also been evaluated. Chromium ions doped alkaline earth zinc borate glasses show BO3 and BO4 structural units in the FT-IR studies.

Preparation and characterization of Tb3+ ions doped zincborophosphate glasses for green emission

The present study reports the preparation of various concentrations of Tb3+ ions doped zincborophosphate glasses and analysis by XRD, FTIR, optical, emission and decay curve spectras. The effect of borate groups on the phosphate was evidenced by FTIR spectroscopy. The JO intensity parameters was calculated using Judd-Offlet theory. The fluroscence spectra of Tb3+ doped zincborophosphate glasses revealed the efficient blue and green emissions due to 5D3 and 5D4 excited levels to 7Fj ground state respectively. The decay curves exhibits single exponential curves for all the Tb3+ ion concentrations. Various radiative and fluorescence parameters are calculated using JO intensity parameters. Based on the results obtained in the present study, the Tb3+ ions doped zincborophosphate glasses behaves as a efficient laser active materials for highintensity emissions in the green region.

Spectroscopic studies of Cr3+ ions doped in poly(vinylalcohol) complexed polyethylene glycol polymer films

Polymer films of Poly(vinylalcohol) (PVA) complexed with Polyethylene glycol (PEG) with different dopant concentrations of Cr3+ ions are prepared by solution cast technique. Electron paramagnetic resonance (EPR), Optical absorption and FT-IR studies have been carried out on the polymer films. The EPR spectra of the entire samples exhibit resonance signal at g ≈1.97 which is attributed to the isolated Cr3+ pairs. The temperature variation EPR studies show that the population of spin-levels participating in the resonance decreases with an increase in temperature, which is in accordance with the Boltzmann Law. The paramagnetic susceptibilities (X) have been calculated from the EPR data at different temperatures. The linewidth of the g ≈1.97 resonance signal has been found to be decreasing with an increase in temperature, which confirms the pairing mechanism between Cr3+ ions. The Optical absorption spectrum of chromium ions in (PVA+PEG) polymer films exhibits three bands, corresponding to the d-d transitions...

Spectroscopic properties of (PVA+ZnO):Mn2+ polymer films

Electron Paramagnetic Resonance (EPR), optical absorption and infrared spectral studies have been carried out on Mn2+ ions doped in poly(vinyl alcohol) complexed with zinc oxide polymer films prepared by solution cast technique. The EPR spectra of 1 mol% Mn2+ ions doped polymer complex (PVA+ZnO) at room temperature exhibit sextet hyperfine structure (hfs), centered at 2.01. The spin-Hamiltonian parameter values indicate that the ground state of Mn2+ ion in d5 and the site symmetry around Mn2+ ions in tetragonally distorted octa hedral site. The optical absorption spectra exhibits two bands centered at 275nm at 437nm. The FTIR spectrum exhibits bands characteristic of stretching and banding vibrations of O-H, C-H and C=C groups.