Spectroscopic properties and martensitic phase transition of Y4Al2O9:Ce single crystals under high pressure
Yongjie Wang , R. Hrubiak , Sebastian Turczyński , D.A. Pawlak , Michał Malinowski , Damian Włodarczyk , K. Kosyl , W. Paszkowicz , H. Przybylinska , A. Wittlin , A. Kamińska , Ya Zhydachevskyy , M.G. Brik , Lily Li , Chong-Geng Ma , Andrzej Suchocki
AbstractHigh pressure studies of monoclinic yttrium aluminum oxide single crystals (Y4Al2O9-YAM) doped with Ce3+ ions grown by micro-pulling-down method are report ed. The results of absorption measurements in the mid-infrared prove the existence of four different sites in which Ce3+ ions substitute Y ions, in accordance with the crystallo graphic structure of YAM. The lowest 5d level of Ce3+ is located very close to the bottom of the conduction band for two of four Ce3+ related centers at ambient pressure, which results in strong temperature quenching of their luminescence. Two other Ce3+ centers do not emit at ambient pressure since their 5d levels are resonant with the conduction band. Application of high pressure above 11 GPa restores their luminescence. Consequences of such energy structure of various Ce3+ sites in YAM for the Dorenbos theory are discussed. The bandgap energy of YAM is found to be 5.93 eV, which is the smallest out of the three yttrium aluminum oxides. High-pressure synchrotron angle dispersive x-ray di ffraction and Raman scattering measurements identify a phase transition occurring at pressures between 8 and 11 GPa, which has martensitic character. The second phase transition to another structure (likely with hexagonal symmetry) occurs at a pressure around 16 GPa.
|Journal series||Acta Materialia, ISSN 1359-6454, (A 45 pkt)|
|No||15 February 2019|
|Publication size in sheets||0.5|
|Keywords in English||Single crystal; Luminescence; High pressure; X-ray diffraction; Phase transition|
|Score|| = 45.0, ArticleFromJournal|
= 45.0, ArticleFromJournal
|Publication indicators||: 2017 = 2.737; : 2017 = 6.036 (2) - 2017=6.174 (5)|
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