Thermally stable phosphors with efficient visible emission are essential for next-generation white light-emitting diodes (WLEDs). Herein, Dy3+-activated CaZrO3 phosphors were synthesized via a conventional solid-state reaction and systematically investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and photoluminescence spectroscopy. The phosphors exhibit characteristic greenish-yellow emissions at 482 and 576 nm, corresponding to the 4F₉/₂ → 6H₁₅/₂ (magnetic dipole) and 4F₉/₂ → 6H₁₃/₂ (electric dipole) transitions of Dy3+, respectively. Concentration quenching is primarily governed by enhanced nonradiative relaxation at higher Dy3+ concentrations. Notably, the optimized phosphor retains ~71% of its initial emission intensity at 483 K, demonstrating excellent thermal stability. These results highlight Dy3+-activated CaZrO3 as a promising phosphor for high-performance WLED applications with improved color quality and thermal reliability.
Near-infrared (NIR) interaction spectroscopy enables non-contact, non-destructive assessment of water content in dried salt-cured whitefish (clipfish), but structural heterogeneity alters photon transport and limits calibration robustness. This study investigates how drying-related changes in photon transport govern spectra and calibration behaviour. NIR interactance spectra (761–1081nm) were acquired from 108 intact dried salt-cured whitefish (two positions per fish) across four production batches using five illumination–detection offsets from 6.5 to 18.5mm. For two batches (58 fish), measurements were repeated after removal of the surface salt layer. Monte Carlo simulations in a two-layer system investigated how absorption, scattering, salt-layer development, and sampling geometry govern spectral variation. Partial least squares (PLS) regression models were calibrated using 116 samples and tested using 99 samples from two independent batches. Spectral variation with water content was governed primarily by formation of a highly scattering salt layer rather than by changes in muscle absorption. Measurements exhibited regime-dependent behaviour consistent with muscle-dominated sampling, salt-layer development, and a stabilised salt layer limiting muscle sensitivity. For absorbance and intensity-normalised spectra, external SEP ranged from 0.69–1.19% and 1.11–1.53% for the two test batches, with biases of 1.50–3.15% and -0.05 to -3.31%, respectively. Sampling geometry revealed a trade-off between sampling depth and signal strength. Intensity-related variation, often removed through spectral pre-processing, contained physically meaningful information linked to structural evolution. These results establish a physics-based framework for interpreting NIR interactance calibration behaviour and guiding measurement strategies toward robust, transferable NIR measurements in layered, structurally evolving products.
Atmospheric-pressure Ar/CF4 microwave plasma jets are vital for precision optical fabrication and surface fluorination. However, spectroscopic characterization of their reactive fluorocarbon species remains challenging. Here, we present a combined experimental and computational study on a low-power (≤10 W) Ar/CF4 microwave plasma jet. High-resolution optical emission spectroscopy is employed to resolve the rovibrational structures of key molecular emitters, including the C2 Swan bands (d3Πg–a3Πu) and the OH (A2Σ–X2Π) band. From these spectra, the gas temperature (823–2278 K) and effective vibrational temperature (1910–3340 K) are derived via detailed spectral fitting. The electron density is determined independently from Stark broadening of the Hα line. To overcome OES limitations for non-emissive species, a zero-dimensional global model is developed and critically benchmarked against the experimental spectral trends. The model predictions show good qualitative agreement with the experimental trends, suggesting that the electron density reduction with increasing CF4 is likely dominated by enhanced inelastic collisional losses (raising electron temperature) rather than direct electron attachment, as supported by combined Stark broadening analysis and simulated particle balances. The model further shows a transition in CF4 dissociation pathways. This work establishes a combined spectroscopic diagnosis and modeling framework, providing a mechanistic understanding of energy transfer and reaction kinetics in fluorocarbon microwave plasmas through quantitative molecular spectroscopy.
