Single crystal growth, structure and magnetic properties of Pr₂Hf₂O₇pyrochlore

Abstract

Abstract. Large single crystals of the pyrochlore Pr 2 Hf 2 O 7 have been successfully grown by the floating zone technique using an optical furnace equipped with high power Xenon arc lamps. Structural investigations have been carried out by both synchrotron X-ray and neutron powder diffraction to establish the crystallographic structure of the materials produced. The magnetic properties of the single crystals have been determined for magnetic fields applied along different crystallographic axes. The results reveal that Pr 2 Hf 2 O 7 is an interesting material for further investigations as a frustrated magnet. The high quality of the crystals produced make them ideal for detailed investigations, especially those using neutron scattering techniques.

Tuning the Pr Valence State To Design High Oxygen Mobility, Redox and Transport Properties in the CeO2–ZrO2–PrOx Phase Diagram

“…Furthermore, magnetic measurements of Ce 1– x Zr x O 2 solid solutions annealed under air at high temperatures show diamagnetic signals and consequently the absence of Ce 3+ . Therefore, within our experimental measurement conditions ( T < 400 K), we can assume the only presence of a Pr 4+ /Pr 3+ mixture and 100% Ce 4+ so that all Curie constants can be calculated per mole of praseodymium only. − …”

“…Taking into account the theoretical effective moments of Pr 4+ and Pr 3+ ions (2.54 and 3.58 μ B , respectively, C Pr 4+ = 0.806 emu K/mol, C Pr 3+ = 1.602 emu K/mol), their proportion can be evaluated for all of the Ce 1– x – y Zr x Pr y O 2– z series (Table and Figure ). At low temperature ( T < 175 K), a slight deviation of the Curie–Weiss law must be mentioned, leading to consider the more general Van Vleck formula taking into account the various populations of fundamental and excited states and the spin–orbit coupling effect. − …”

“…Taking into account the theoretical effective moments of Pr 4+ and Pr 3+ ions (2.54µB and 3.58µB, respectively, CPr4+= 0.806 uem.K/mole, CPr3+= 1.602 uem.K/mole), their proportion can be evaluated for all the Ce1-x-yZrxPryO2-z series (Table 2 and Figure 3). At low temperature (T<175K), a slight deviation to the Curie-Weiss law must be mentioned leading to consider the more general Van-Vleck formula taking into account the various population of fundamental and excited states and the spin-orbit coupling effect [26][27][28][29][30][31][32] . Table 2: Curie constants values, Pr 4+ /Pr 3+ molar ratios and Weiss temperature of Ce1-x-yZrxPryO2-z oxides annealed at 700°C under air, deduced from Curie-Weiss law 1/=(T-p)/C.…”

Photoluminescence and Scintillation Properties of Ce-, Pr-, and Tb-doped (Gd,Lu)2Hf2O7 Crystals

“…(26)(27)(28)(29)(30)(31) However, a single-crystal form is preferable for X-or γ-ray measurements owing to their high optical transparency, density, and homogeneity. Since the crystal growth of RE 2 Hf 2 O 7 is difficult owing to the high melting points (~2400 °C), there have only been a few reports on the crystal growth of pyrochlore RE 2 Hf 2 O 7 (e.g., Nd 2 Hf 2 O 7 (32) and Pr 2 Hf 2 O 7 (33) ). In our previous works, La 2 Hf 2 O 7 , Gd 2 Hf 2 O 7 , and Lu 2 Hf 2 O 7 single crystals were successfully synthesized using an optical floating zone furnace equipped with Xe lamps, and the scintillation properties of the single crystals were reported for the first time.…”

Scintillation Properties of Ti- and Zr-doped Gd2Hf2O7 Crystals

“…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. (16)(17)(18) Previously, we introduced the optical floating zone (FZ) method as an effective and powerful technique for searching new oxide scintillators with high melting points. (19)(20)(21)(22)(23) Up to now, pyrochlore RE 2 Hf 2 O 7 (RE = La, Gd, Lu) single crystals have been prepared using an optical FZ furnace equipped with Xe lamps, and the scintillation properties of these single crystals were reported for the first time by Nakauchi et al (18) To improve scintillation characteristics by increasing oxygen vacancies, Zr and Ti ions with radii smaller than that of the Hf ion are introduced into RE 2 Hf 2 O 7 single crystals to distort the crystal lattice because Hf-based oxide materials typically show luminescence due to oxygen vacancies such as F and F + centers.…”