Structure-Property Correlations in Neodymium-doped Sr 2 ZnTeO 6 : Insights into Optical and Dielectric Analysis
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This study investigates the optical, structural, and dielectric characteristics of Nd-doping in Sr₂Zn₁- x Nd x TeO₆ (0 ≤ x ≤ 0.2) double perovskite ceramics synthesised via the solid-state reaction technique. Structural analysis, performed through room-temperature X-ray diffraction and Rietveld refinement, confirmed a monoclinic I2/m structure, with microstrain and crystallite size being influenced by the Nd 3+ content. The successful substitution of Nd 3+ for Zn 2+ was evident from the consistency in the peak positions for all compositions. Reitveld refinement indicated variations in unit cell volume in all compositions. Variations in tolerance factor ‘τ’ and tilting angle ‘ɸ’ stated existence of octahedral tilting. The FTIR spectra exhibit key absorption bands corresponding to metal–oxygen bonding modes within the perovskite lattice. Notably, peaks near 470 cm⁻¹,539.5 cm⁻¹, and 656 cm⁻¹ correspond to Zn-O and Te–O bending and stretching modes, in ZnO 6 and TeO 6 octahedra. Additional features around 678 cm⁻¹ and 709 cm⁻¹ are linked to Te-O overtones or antisymmetric stretches. With increasing Nd³⁺ substitution (x = 0.0 to 0.2), peaks shift to lower wavenumber, broaden, and show reduced transmittance, indicating lattice distortion and weakening metal-oxygen bonding because of a larger ionic radius of Nd 3+ replacing Zn 2+ . Despite these changes, the double perovskite structure remains intact with altered local vibrational dynamics. UV-Visible studies indicated a drop in band gap from 3.77 eV in undoped composition to 3.52 eV for x = 0.2, with increasing Nd doping content, indicating an enhancement in conductivity. This is also an indication that Nd doping initiates new electronic states within the bandgap, minimising energy for required electronic transitions.FESEM and EDX analyses revealed homogeneous distribution of Nd ions and grain evolution with doping, while FTIR and Raman spectroscopy provided insights into lattice vibrations and bond modifications. Dielectric analysis revealed frequency and temperature-dependent behaviour, characterised by an enhanced dielectric constant and conductivity at optimal doping levels. The results suggest that the material is suitable for applications in high-energy storage and optoelectronic devices.
