Cr‐doped ZnAl₂O₄: Microwave solution route for ceramic nanoparticles from metalorganic complexes in minutes

Abstract

A combination of microwave irradiation and metalorganic precursors in solution was used for the synthesis of Cr:ZnAl2O4 nanoparticles with high yields (~92%). Though the spinel phase is formed after ~40 minutes, 60 minutes of microwave irradiation was required for the complete transformation of precursors into the spinel. The as‐prepared material is nanocrystalline and phase‐pure and was subjected to annealing in air at different temperatures. Annealing improved the crystallinity, and the material turned pink at 1200°C. The structural and optical properties were investigated by XRD, HR‐TEM, FE‐SEM, FT‐IR, diffuse reflectance spectroscopy, and photoluminescence spectroscopy. The two bands in the excitation spectra (400 and 540 nm) became more intense as the annealing temperature was raised. The 400 nm band was asymmetric and consisted of two peaks, suggesting a trigonal distortion. The emission spectra consisted of a zero phonon line (ZPL), along with its associated multi‐phonon side bands. The high Dq/B (3.21) suggested the presence of Cr3+ in a strong crystal field. With annealing, the emission lifetimes increased from ~7 to ~34 ms. This work demonstrates rapid, low‐temperature synthesis of a red‐emitting phosphor, with potential applications in bio‐imaging, sensors, and lighting.

Synthesis and investigation of dielectric properties of nanoceramic composite material for microwave applications

“…Table 1 shows the comparison of reported works with the present one. The reported crystallite size was observed to be in the range of 16–40 nm [21, 26–30], whereas extremely small crystallite ∼3.7 nm was reported which can be assigned to the hydrothermal process along with the choice of high calcination temperature of 1200°C [31]. In the present study, we first synthesised the TiO 2 nanoparticles by chemical route which was further employed in the sol–gel synthesis of ZnAl 2 O 4 TiO 2 .…”

Post annealing induced manipulation of phase and upconversion luminescence of Cr3+ doped NaYF4:Yb,Er crystals

“…The two noticeable bands at 271 nm and 376 nm can be assigned to the 4 A 2g (F) / 4 T 1g (P), 4 A 2g (F) / 4 T 1g (F) allowed transitions of Cr 3+ ions. 47 The FESEM studies carried out for the samples annealed at 600 C with different concentrations of Cr 3+ ion (ESI S2 †).…”

Correlation between B value deviation and sintering temperature of perovskite solid solution materials

“…The diffraction peak intensity is the highest when the LCM content is 25%, which indicates that the system of BST‐LCM material has the best crystallinity. When the LCM content in the solid solution is 25%, the half‐height width is smallest and the narrowest diffraction intensity is the highest . The specific degree of crystallization is detailed in Table ).…”

“…When the LCM content in the solid solution is 25%, the half-height width is smallest and the narrowest diffraction intensity is the highest. [16][17][18][19] The specific degree of crystallization is detailed in Table S5). The 2θ angle no longer moves when the LCM content is 45.91% and 50%, indicating that LCM and BST are completely miscible.…”