In situ Raman and Time-Resolved Luminescence Investigation of the Local Structure of ZrO 2 in the Amorphous to Crystalline Phase Transition

• Published in: Journal of physical chemistry. C Vol. 116; no. 31; pp. 16776 - 16783
• Main Authors: Tiseanu, Carmen, Parvulescu, Vasile I., Cojocaru, Bogdan, Pemartin, Kelly, Sanchez-Dominguez, Margarita, Boutonnet, Magali
• Format: Journal Article
• Language: English
• Published: 09.08.2012
• Subjects: Composites; Europium-Doped Zirconia; Nanocrystals; Nanoparticles; Oxygen Diffusion; Polymorphs; Room-Temperature; Spectroscopy; Stabilized Zirconia; X-Ray-Absorption
• ISSN: 1932-7447; 1932-7455; 1932-7455
• DOI: 10.1021/jp3040538

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.