In situ Raman and time-resolved luminescence investigation of the local structure of ZrO 2 in the amorphous to crystalline phase transition

• The local structure of europium doped and impregnated ZrO 2 in the amorphous state and during crystallization is investigated by in situ X-ray diffraction and in situ Raman, high-resolution transmission electron microscopy (HRTEM) and time-resolved photoluminescence spectroscopy. From Raman spectra excited at three different wavelengths (λ ex= 488, 514, and 633 nm), both phonon modes of ZrO 2 and photoluminescence (PL) corresponding to europium electronic transitions were investigated. In the as-synthetized state, samples were X-ray and Raman amorphous with few tetragonal (also monoclinic) crystallites being observed under HRTEM microscopy. In situ XRD patterns show that all samples crystallize in the tetragonal phase around 450 °C. The time-resolved PL spectra of europium doped and impregnated ZrO 2 show spectral dynamics with time delay after lamp/laser pulse which is assigned to the coexistence of the different amorphous and crystalline components or unreacted europium precursor. From in situ Raman spectra, crystallization was detected at 300-350 °C, monitoring for the characteristic tetragonal-like 5D 0- 7F 2 emission of europium at 606 nm. The ratio of tetragonal to amorphous emission increased abruptly from ca. 2-4% at 300-400 °C to almost 25% at 400-450 °C, whereas at 500 °C the emission is mostly tetragonal. A similar trend was found with the ex situ calcined samples, but relative strong tetragonal emission was observed at lower temperature in the range of 350 to 400 °C.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Kemiteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Chemical Engineering (hsv//eng)

Nyckelord

Europium-Doped Zirconia

X-Ray-Absorption

Stabilized Zirconia

Room-Temperature

Oxygen Diffusion

Nanocrystals

Spectroscopy

Nanoparticles

Composites

Polymorphs

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