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<p>Intense red emission with an enhancement of three times in intensity has been observed on La<sup>3+</sup> substitution in Ca<sub>1−<i>x</i>−<i>y</i></sub>La<sub><i>x</i></sub>TiO<sub>3</sub>:yEu<sup>3+</sup> phosphors, synthesized by modified solution combustion technique employing citrate-gel complexation method. The X-ray diffraction pattern analysis and low- and high-resolution transmission electron microscopic techniques confirm that the nanophosphors exhibit the expected change in unit cell volume due to the substitution of ions while preserving the orthorhombic structure. The atomic compositions of the material obtained by XPS and EDX analysis match well with the theoretical values. Raman studies elaborate the local structure distortion caused by the octahedral tilting due to the incorporation of dopants. The observed enhancement in luminescence properties under both UV (398&#xa0;nm) and blue (465&#xa0;nm) irradiations on La<sup>3+</sup> substitution can be attributed to the higher oscillator strengths for the 4f → 4f electronic transitions occurring due to the reduction in symmetry of crystalline environment of Eu<sup>3+</sup> ions. Herein, the substituent ions occupy the Ca<sup>2+</sup> sites alone as confirmed by the single exponential nature of luminescence decay curves. The optimum phosphor sample Ca<sub>0.88</sub>La<sub>0.05</sub>TiO<sub>3</sub>:0.07Eu<sup>3+</sup> gives a significantly high photoluminescence quantum yield of 78.17% and as temperature rises from 300 to 400&#xa0;K, it retains the luminescence intensity of 75%. The thermal activation energy of 0.36&#xa0;eV, obtained from the analysis of temperature-dependent emission, for the optimum sample, proposes the substantial stability of these phosphors against thermal quenching due to the cross-over process. The increase in the value of J-O parameter Ω<sub>2</sub> from 1.53 × 10<sup>–20</sup> to 3.13 × 10<sup>–20</sup>&#xa0;cm<sup>2</sup> and the asymmetric value from 3.08 to 3.46, on doping of optimum concentration of La<sup>3+</sup> ions, validates high covalency and the highly polarized and asymmetrical local environment of europium ions. Owing to their intense, colour-pure luminescence and superior thermal and chemical stability, these phosphors emerge as promising candidates for optoelectronic applications.</p>

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Enhanced emission in lanthanum-activated CaTiO3:Eu3+ nanophosphors

  • 期刊论文

  • 发表日期：

    2025年8月28日

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  • Sajesh Sasidharan,
  • G. Jyothi,
  • R. Raji,
  • K. G. Gopchandran

摘要

Intense red emission with an enhancement of three times in intensity has been observed on La3+ substitution in Ca1−x−yLaxTiO3:yEu3+ phosphors, synthesized by modified solution combustion technique employing citrate-gel complexation method. The X-ray diffraction pattern analysis and low- and high-resolution transmission electron microscopic techniques confirm that the nanophosphors exhibit the expected change in unit cell volume due to the substitution of ions while preserving the orthorhombic structure. The atomic compositions of the material obtained by XPS and EDX analysis match well with the theoretical values. Raman studies elaborate the local structure distortion caused by the octahedral tilting due to the incorporation of dopants. The observed enhancement in luminescence properties under both UV (398 nm) and blue (465 nm) irradiations on La3+ substitution can be attributed to the higher oscillator strengths for the 4f → 4f electronic transitions occurring due to the reduction in symmetry of crystalline environment of Eu3+ ions. Herein, the substituent ions occupy the Ca2+ sites alone as confirmed by the single exponential nature of luminescence decay curves. The optimum phosphor sample Ca0.88La0.05TiO3:0.07Eu3+ gives a significantly high photoluminescence quantum yield of 78.17% and as temperature rises from 300 to 400 K, it retains the luminescence intensity of 75%. The thermal activation energy of 0.36 eV, obtained from the analysis of temperature-dependent emission, for the optimum sample, proposes the substantial stability of these phosphors against thermal quenching due to the cross-over process. The increase in the value of J-O parameter Ω2 from 1.53 × 10–20 to 3.13 × 10–20 cm2 and the asymmetric value from 3.08 to 3.46, on doping of optimum concentration of La3+ ions, validates high covalency and the highly polarized and asymmetrical local environment of europium ions. Owing to their intense, colour-pure luminescence and superior thermal and chemical stability, these phosphors emerge as promising candidates for optoelectronic applications.