Luminescence study of cerium-doped La2Hf2O7: Effects due to trivalent and tetravalent cerium and oxygen vacancies

On comparison of luminescence properties of La2Zr2O7 and La2Hf2O7 nanoparticles

“…[28][29][30] Eagleman et al observed blue emission in bulk La 2 Hf 2 O 7 powder induced by oxygen vacancies but could not assign the exact types of oxygen vacancies involved. 31 Zhang et al did not observe any appreciable emission from their La 2 Zr 2 O 7 nanocrystals, but after sensitizing with a Pb 2+ ions, they observed weak emission which was attributed to the transition between valence band and oxygen vacancies (mid-gap level). 30 Moreover, the exact structure of oxygen vacancies involved in such luminescence phenomenon (neutral, singly ionized, or doubly ionized) needs to be identified for explicitly proposing exact mechanisms.…”

“…However, the literature pertaining to photoluminescence study in undoped La 2 B 2 O 7 (B = Zr and Hf) and their comparison is completely missing, though there have been reports for Nd 2 Zr 2 O 7 , Gd 2 Zr 2 O 7 , Y 2 Zr 2 O 7 , and Eu 2 Zr 2 O 7 . Eagleman et al observed blue emission in bulk La 2 Hf 2 O 7 powder induced by oxygen vacancies but could not assign the exact types of oxygen vacancies involved . Zhang et al did not observe any appreciable emission from their La 2 Zr 2 O 7 nanocrystals, but after sensitizing with a Pb 2+ ions, they observed weak emission which was attributed to the transition between valence band and oxygen vacancies (mid‐gap level) .…”

Soft chemical synthesis and structural characterization of Y2HfxTi2−xO7

“…The most commonly used method for the preparation of lanthanide hafnate ceramic is via solid-state reaction of metal oxides [7][8][9][10][11][12][13][14][15][16][17][18], including mixed-oxide route via reactive spark plasma sintering [19] or vacuum sintering [20,21]. By employing the traditional mixed oxide processing route, solid state reaction [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] leads to the formation of crystalline Ln 2 Hf 2 O 7 after extended calcination time at high temperature owing to the low specific surface area of the metal oxides at which diffusion reaction occurs.…”

“…By employing the traditional mixed oxide processing route, solid state reaction [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] leads to the formation of crystalline Ln 2 Hf 2 O 7 after extended calcination time at high temperature owing to the low specific surface area of the metal oxides at which diffusion reaction occurs. In addition, this process of grinding/ball-milling in organic solvent (to preserve the stoichiometry of the components), pelleting and sintering is often required to be repeated to allow sufficient interdiffusion of cations for the preparation of single phase samples.…”

Scintillation Properties of Ti- and Zr-doped Gd2Hf2O7 Crystals

“…(10) For scintillator applications, some pyrochlore rareearth hafnates have been investigated only in a polycrystalline form including ceramics and powders. (11)(12)(13)(14)(15) In general, scintillators have been developed in the single crystal form owing to the high optical transparency and homogeneity; however, the growing need is the driving force of developing new scintillators. In the case of rare-earth hafnate, since crystal growth is quite difficult because of the high melting point (~2400 °C), few studies on the growth of pyrochlore rare-earth hafnate compounds have been reported.…”