C. K. Mahadevan

Modulating the local coordination environment of the luminescent centers represents a compelling strategy for designing high‐performance red phosphors. However, it remains challenging for Eu‐doped phosphors to simultaneously achieve high internal quantum efficiency and negative thermal quenching performance. In this work, Ca ₂ AlNbO ₆ was selected as the matrix. The spatial arrangement of the Ca sites provides relatively separated substitutional positions for Eu, contributing to the high optimal Eu concentration of x = 0.18. At the optimized W concentration (y = 0.02), W incorporation modifies the local crystal field of Eu through structural coupling and enhances the local lattice rigidity. As a result, the phosphor exhibits a 3.98‐fold enhancement in emission intensity, an internal quantum efficiency of 98.2%, and an emission intensity of 121% at 423 K relative to that at 303 K. The fabricated white light‐emitting diode (WLED) presents a color temperature of 4238 K, and a color rendering index of 92.1. This work provides a feasible strategy for simultaneously optimizing luminescence efficiency and thermal stability in Eu ⁻ activated double‐perovskite phosphors.

There are many solid materials existing as different structural and other phases (polymorphs), when prepared with different conditions; they exhibit different physicochemical properties. It is important to consider the preparation of all these crystalline phases (along with amorphous phase), at nanoscale, in their pure form by using facile and cost-effective methods. Our study with nickel sulphide is considered here to illustrate this. Nickel sulphide exhibits three prominent phases which are: α-NiS, β-NiS and NiS1.03. These crystalline (and amorphous NiS1.03) nanophases along with doped α-NiS nanocrystals (doped with Cd2+, Fe2+ and O2−) have been successfully prepared in high purity using a facile solvothermal route (with the use of commercially availabe microwave oven); and they were charcterized physicochemically (chemically, structurally, optically, magnetically and electrically) using available standard methods. Obtained results indicate that the facile method adopted for the preparation is found to be an effective and cost-effective one. The role of XRD and TG/DTA measurements is found to be important in this preparation. A brief review is made in this direction.