Structural and vibrational properties of single crystals of Scandia, Sc2O3 under high pressure

Abstract

We report the results of single-crystal X-ray diffraction and Raman spectroscopy studies of scandium oxide, Sc2O3, at ambient temperature under high pressure up to 55 and 28 GPa, respectively. Both X-ray diffraction and Raman studies indicated a phase transition from the cubic bixbyite phase (so-called C-Res phase) to a monoclinic C2/m phase (so-called B-Res phase) at pressures around 25–28 GPa. The transition was accompanied by a significant volumetric drop by ∼6.7%. In addition, the Raman spectroscopy detected a minor crossover around 10–12 GPa, which manifested in the appearance of new and disappearance of some Raman modes, as well as in softening of one Raman mode. We found the bulk modulus values of the both C-Res and B-Res phases as B0 = 198.2(3) and 171.2(1) GPa (for fixed B′ = 4), respectively. Thus, the denser high-pressure lattice of Sc2O3 is much softer than the original lattice. We discuss possible mechanisms that might be responsible for the pronounced elastic softening in the monoclinic high-pressure phase in this “simple” oxide with an ultra-wide band gap.

Structural and Lattice-Dynamical Properties of Tb2O3 under Compression: A Comparative Study with Rare Earth and Related Sesquioxides

“… 13 , 14 The effect of HP on RE SOs has been extensively studied by several research groups, and their pressure-induced PTs have been recently reviewed. 15 In fact, since the cubic phase can be synthesized in a number of them, from Lu to Sm as well as in Mn 2 O 3 , In 2 O 3 , and Tl 2 O 3 , its behavior under compression has been widely studied, as for instance in Lu 2 O 3 , 16 , 17 Yb 2 O 3 , 18 , 19 Tm 2 O 3 , 20 , 21 Er 2 O 3 , 22 − 24 Ho 2 O 3 , 25 − 28 Dy 2 O 3 , 29 , 30 Gd 2 O 3 , 31 − 38 Eu 2 O 3 39 − 45 Sm 2 O 3 , 34 , 46 , 47 Sc 2 O 3 , 48 − 50 Y 2 O 3 , 34 , 51 − 61 Mn 2 O 3 , 62 − 65 In 2 O 3 , 66 − 70 and Tl 2 O 3 . 71 Moreover, the equation of state of several RE SOs of C-, B-, and A-type has been studied comparatively.…”

“…Since the molar volume (density) of the A-, B-, and C-type phases decreases (increases) in the order C, B, and A, the PT sequence C → B → A is expected for most RE SOs crystallizing in the cubic phase, either at high pressure (HP) or at high temperature (HT). , The effect of HP on RE SOs has been extensively studied by several research groups, and their pressure-induced PTs have been recently reviewed . In fact, since the cubic phase can be synthesized in a number of them, from Lu to Sm as well as in Mn 2 O 3 , In 2 O 3 , and Tl 2 O 3 , its behavior under compression has been widely studied, as for instance in Lu 2 O 3 , , Yb 2 O 3 , , Tm 2 O 3 , , Er 2 O 3 , − Ho 2 O 3 , − Dy 2 O 3 , , Gd 2 O 3 , − Eu 2 O 3 − Sm 2 O 3 , ,, Sc 2 O 3 , − Y 2 O 3 , ,− Mn 2 O 3 , − In 2 O 3 , − and Tl 2 O 3 . Moreover, the equation of state of several RE SOs of C-, B-, and A-type has been studied comparatively …”

“…13,14 The effect of HP on RE SOs has been extensively studied by several research groups and their pressure-induced PTs have been recently reviewed. 15 In fact, since the cubic phase can be synthesized in a number of them, from Lu to Sm as well as in Mn2O3, In2O3 and Tl2O3, its behavior under compression has been widely studied, as for instance in Lu2O3, 16,17 Yb2O3, 18,19 Tm2O3, 20,21 Er2O3, [22][23][24] Ho2O3, [25][26][27][28] Dy2O3, 29,30 Gd2O3, [31][32][33][34][35][36][37][38] Eu2O3 [39][40][41][42][43][44][45] Sm2O3, 34,46,47 Sc2O3, [48][49][50] Y2O3, 34,[51][52][53][54][55][56][57][58][59][60][61] Mn2O3, [62][63][64]…”

Correlated structural and electronic phase transformations in transition metal chalcogenide under high pressure

“…Despite the broad interest on Cr 2 S 3 , few previous experimental and theoretical results can be referred on the structural and electrical transportation information under high pressure. Most structure studies under high pressure have been devoted to A 2 X 3 -type transition metal sesquioxides compared to chalcogenides, [11][12][13][14][15][16][17][18] due to their vital application in the process of ceramics as additives, grain growth inhibitors, and phase stabilizers. 19 Cr 2 O 3 , which is isoelectronic with Cr 2 S 3 , was found absent of structural phase transition to 10 GPa (Refs.…”

First-principles calculations and Raman scattering evidence for local symmetry lowering in rhombohedral ilmenite: temperature- and pressure-dependent studies

“…We will extend our theoretical analysis based on group-theory to confirm the earlier model in describing the enlarged number of Raman modes at low temperature. An alternative method for reducing the atomic bond is to put the material under high hydrostatic pressure conditions [71,72]. In this way, Raman spectra for the Il-type CdTiO 3 were recorded under pressure at room temperature.…”