Influence of annealing temperature on the phase transformation of Al2O3

Mahat, Annie Maria; Mastuli, Mohd Sufri; Kamarulzaman, Norlıda

doi:10.1063/1.4941627

Cited by 5 publications

(3 citation statements)

References 21 publications

(22 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For instance, the dehydration of chromium hydroxide leads directly to the formation of α-Cr 2 O 3 at a temperature above 400 • C, whereas the dehydration of aluminum hydroxide proceeds through the formation of aluminum oxyhydroxides, and then via different metastable alumina polymorphs, such as γ, δ, and θ, whose structure differs significantly from α-Cr 2 O 3 . The formation of α-Al 2 O 3 , which is isostructural with eskolaite, occurs only at a temperature above 1000 • C [32].…”

Section: Resultsmentioning

confidence: 99%

The Formation of Cr-Al Spinel under a Reductive Atmosphere

et al. 2021

View full text Add to dashboard Cite

In the present work, for the first time, the possibility of formation of CrAl2O4 was shown from the equimolar mixture of co-precipitated Al2O3 and Cr2O3 oxides under a reductive environment. The crystallographic properties of the formed compound were calculated using the DICVOL procedure. It was determined that it has a cubic crystal structure with space group Fd-3m and a unit cell parameter equal to 8.22(3) Å. The formed CrAl2O4 is not stable under ambient conditions and easily undergoes oxidation to α-Al2O3 and α-Cr2O3. The overall sequence of the phase transformations of co-precipitated oxides leading to the formation of spinel structure is proposed.

show abstract

Section: Resultsmentioning

confidence: 99%

The Formation of Cr-Al Spinel under a Reductive Atmosphere

et al. 2021

View full text Add to dashboard Cite

show abstract

“…More than 30% of the energy is converted into heat which reduces the LED luminescent efficacy and lifetime. Recently, high-color rendering index (CRI) micro-white LEDs have been fabricated including blue-emitting InGaN-nanowire devices and red-emitting fluoride nanophosphors. , Although fluoride phosphors exhibit intensive red emission and easy preparation, they are unstable with high humidity and low thermal conductivity. , Recently, aluminum oxides such as α-Al 2 O 3 :Mn 4+ , Mg 2+ ; BaMgAl 10 O 17 :Mn 4+ , Mg 2+ ; BeAl 2 O 4 :Mn 4+ ; Y 3 Al 5 O 12 :Mn 4+ , Mg 2+ ; Lu 3 Al 5 O 12 :Mn 4+ , Mg 2+ ; and CaGdAlO 4 :Mn 4+ , Mg 2+ (Mg 2+ as charge compensation ions), prepared via a solid-state reaction at high temperature 1200–1750 °C, have been intensively studied for improving the color reproduction of thin-film white LEDs due to their high red emission intensity, hardness, and good thermal stability. − The crystal-phase transitions with temperatures of the alumina material have been reported . However, only few studies reported the luminescence properties of Mn 4+ doped into different Al 2 O 3 nanocrystal phases.…”

Section: Introductionmentioning

confidence: 99%

“…19 − 25 The crystal-phase transitions with temperatures of the alumina material have been reported. 26 However, only few studies reported the luminescence properties of Mn 4+ doped into different Al 2 O 3 nanocrystal phases. In this work, we have prepared Al 2 O 3 :Mn 4+ , Mg 2+ (ALO) nanosheets via a hydrothermal route.…”

Section: Introductionmentioning

confidence: 99%

Highly Stable White Light Emission from III-Nitride Nanowire LEDs Utilizing Nanostructured Alumina-Doped Mn⁴⁺ and Mg²⁺

Doan

Tran

et al. 2023

ACS Omega

View full text Add to dashboard Cite

In this report, red-emitting alumina nanophosphors doped with Mn 4+ and Mg 2+ (Al 2 O 3 :Mn 4+ , Mg 2+ ) are synthesized by a hydrothermal method using a Pluronic surfactant. The prepared samples are ceramic-sintered at various temperatures. X-ray diffraction shows that Al 2 O 3 :Mn 4+ , Mg 2+ annealed at 500 °C exhibits a cubic γ-Al 2 O 3 phase with the space group Fd3m-227. The tetragonal δ-Al 2 O 3 and rhombohedral α-Al 2 O 3 phase is obtained at 1000 and 1300 °C, respectively. Cube-like nanoparticles in a size of ∼40 nm are observed for the alumina heated at 500−1000 °C. The size and red-emitting intensity of the phosphors remarkably increased with annealed temperature ∼1300 °C. Emission spectra of the phosphors show strong peaks at 678 and 692 nm due to 2 E g → 4 A 2 transitions of the Mn 4+ ion, under a light excitation of 460 nm. A strong zero-phonon line (ZPL) emission is observed in the luminescence spectra of δ-Al 2 O 3 :Mn 4+ , Mg 2+ at 298 K, whereas a weak one is observed in those of αand γ-Al 2 O 3 :Mn 4+ , Mg 2+ . The alumina phosphors exhibited an excellent waterproof ability during 60 days in water and good thermal stability in the range of 77−573 K. A warm-white light-emitting diode (WLED) fabricated using In x Ga 1−x N nanowire chips with Al 2 O 3 :Mn 4+ , Mg 2+ red-emitting nanophosphors presents a high color rendering index of ∼95.1 and a low correlated color temperature of ∼4998 K. Moreover, the current−voltage characteristic of the nanowire LEDs could be improved using Al 2 O 3 :Mn 4+ , Mg 2+ nanophosphors which is attributed to the increased heat dissipation in the nanowire LEDs.

show abstract

Superior photosensing performance by Ag nanoparticles textured Al2O3 thin film based device

et al. 2023

View full text Add to dashboard Cite

Influence of annealing temperature on the phase transformation of Al2O3

Cited by 5 publications

References 21 publications

The Formation of Cr-Al Spinel under a Reductive Atmosphere

The Formation of Cr-Al Spinel under a Reductive Atmosphere

Highly Stable White Light Emission from III-Nitride Nanowire LEDs Utilizing Nanostructured Alumina-Doped Mn⁴⁺ and Mg²⁺

Superior photosensing performance by Ag nanoparticles textured Al2O3 thin film based device

Contact Info

Product

Resources

About

Influence of annealing temperature on the phase transformation of Al2O3

Cited by 5 publications

References 21 publications

The Formation of Cr-Al Spinel under a Reductive Atmosphere

The Formation of Cr-Al Spinel under a Reductive Atmosphere

Highly Stable White Light Emission from III-Nitride Nanowire LEDs Utilizing Nanostructured Alumina-Doped Mn4+ and Mg2+

Superior photosensing performance by Ag nanoparticles textured Al2O3 thin film based device

Contact Info

Product

Resources

About

Highly Stable White Light Emission from III-Nitride Nanowire LEDs Utilizing Nanostructured Alumina-Doped Mn⁴⁺ and Mg²⁺