Strain engineered pyrochlore at high pressure

Abstract

Strain engineering is a promising method for next-generation materials processing techniques. Here, we use mechanical milling and annealing followed by compression in diamond anvil cell to tailor the intrinsic and extrinsic strain in pyrochlore, Dy2Ti2O7 and Dy2Zr2O7. Raman spectroscopy, X-ray pair distribution function analysis, and X-ray diffraction were used to characterize atomic order over short-, medium-, and long-range spatial scales, respectively, under ambient conditions. Raman spectroscopy and X-ray diffraction were further employed to interrogate the material in situ at high pressure. High-pressure behavior is found to depend on the species and concentration of defects in the sample at ambient conditions. Overall, we show that defects can be engineered to lower the phase transformation onset pressure by ~50% in the ordered pyrochlore Dy2Ti2O7, and lower the phase transformation completion pressure by ~20% in the disordered pyrochlore Dy2Zr2O7. These improvements are achieved without significantly sacrificing mechanical integrity, as characterized by bulk modulus.

Thermally Induced Disorder–Order Phase Transition of Gd2Hf2O7:Eu3+ Nanoparticles and Its Implication on Photo- and Radioluminescence

“…Hence, they are considered as similar phases but with different degrees of anion and cation ordering. The phase transition is normally induced by chemical doping, 9 pressure, 10 temperature, 11 irradiation, 12 and so forth. The ionic radius ratio (IRR) plays an important role in the structural phase transition of DF ⇄ OP.…”

Pressure-induced phase transition of La2Zr2O7 and La0.5Gd1.5Zr2O7 pyrochlore

“…La 2 Zr 2 O 7 and La 0.5 Gd 1.5 Zr 2 O 7 underwent a pressure-induced phase transition at above 22 GPa. The onset of the high-pressure stable phase is identied by a new reection arising between the (222) and (400) reections of pyrochlore, 17,23 and the highpressure phase is a Pnma cotunnite-like phase. The onset of the high-pressure phase is approximately equivalent for both La 2 Zr 2 O 7 and La 0.5 Gd 1.5 Zr 2 O 7 (22.7 and 23.3 GPa, respectively).…”

“…In previous studies, the increase in the scattering intensity between the (222) and (400) pyrochlore structures has been used to dene the onset of the transition because this is the most intense of the cotunnite peaks. 17,23 Here, we use the intensity ratio I/I 222 between the intensities of the most intense peak of the cotunnite phase and the (222) peak of the pyrochlore to describe the phase ratio of the high-pressure phase and with pressure is determined by the volume change in the transition. Liner ts yield a slope of ln I/I 222 with a pressure of 0.20 GPa À1 , which is lower than that of La 0.5 -Gd 1.5 Zr 2 O 7 0.32 GPa À1 .…”

“…In this manuscript, high pressure phase stability and compression behavior of the two samples are provided. The annealing temperature has an effect on the high-pressure stability and compression behavior, 17,18 and in our study, the sample preparation process is carefully controlled.…”

A Comparison of Order-Disorder in Several Families of Cubic Oxides

“…Over the past two decades, there has been intense interest in defect chemistry, disorder, solid solution formation, and phase transitions in oxide pyrochlores (Glerup et al, 2001;Shlyakhtina et al, 2004;Liu et al, 2004;Knee et al, 2005;Mandal et al, 2006;Matsuhira et al, 2007;Zhang et al, 2008;Clements et al, 2011;Wang et al, 2011;de los Reyes et al, 2013;Zhang et al, 2013;Zhang et al, 2014;Popov et al, 2016;Paul et al, 2016;Rittman et al, 2017a;Rittman et al, 2017b;Simeone et al, 2017;Ponnilavan et al, 2019;Popov et al, 2020;Marlton et al, 2021;Panghal et al, 2021). Because the pyrochlore structure is a derivative of fluorite, it belongs to a large family of related structures.…”