Powder Diffraction Data for the Imperfect Pyrochlore Terbium Titanate, Tb₂Ti₂O₇

Abstract

Notwithstanding expectations of a pure pyrochlore structure (cubic space group Fd3m (227) with Z=8) terbium titanate turns out, like many pyrochlore compounds, to be slightly disordered in the cation and the oxygen lattice so that it partially (for 10%) resembles a structure with fluorite properties (space group Fm3m (225) with Z = 2).

Structural properties of the geometrically frustrated pyrochloreTb2Ti2OHan1, Gardner2, Booth3 2004Phys. Rev. B513320View full textAdd to dashboardCite

“…The discrepancy between our results and those of van de Velde et al 22 must be attributable to either the different techniques used to measure the structure or to produce the sample. Since powder x-ray diffraction should be able to distinguish the cations, we must assume that the synthesis method used in van de Velde et al, namely, preparing Tb 2 Ti 2 O 7 by the citrate method from TiO(OH) 2 and a solution of Tb 4 O 7 in nitric acid, results in an imperfect pyrochlore lattice.…”

“…15 Very recently, Lian et al 14 reported an x-ray diffraction study of the entire RE 2 Ti 2 O 7 (RE=rare-earth) series. Although they do not focus on Tb 2 Ti 2 O 7 or on the detailed search for lattice disorder presented here, they report a room-temperature x parameter for the oxygen 48f site of 0.3281(5), which is consistent with our measurement of 0.3279(1), but not with the value of 0.317(2) 34 found by van de Velde et al 22 A value of x ≈ 0.328 is, however, consistent with that found in the RE 2 Ti 2 O 7 series, 14 while a value less than 0.32 is a gross deviation. As noted earlier, this parameter is very sensitive to lattice distortions, which could be due to antisite disorder, oxygen excess or deficiency, etc.…”

Epitaxial stabilization of (111)-oriented frustrated quantum pyrochlore thin films

“…However, from the bulk result, it is known that the lattice constant of Tb 2 Ti 2 O 7 is very sensitive to the growth condition; specifically, depending on the synthesis technique, the lattice constant can vary from 10.127 Å 89 to above 10.15 Å. 56,57,90 As clearly seen in Fig. 3 (a), Er 2 Ti 2 O 7 and Yb 2 Ti 2 O 7 shows film peaks at higher angles than substrate peaks.…”

“…52,55 Another challenge is the difficulty of fabricating high-quality single-crystalline samples with low disorders, which hinders the intrinsic QSI physics and unavoidably gives rise to inconsistency between experiments. [56][57][58][59][60][61][62][63] To address these challenges, it is thus critical to develop new methods of materials synthesis that are distinct from the conventional solid-state synthesis route to unveil the true nature of frustrated quantum pyrochlores.…”

Structures and Stabilities of Trivalent and Tetravalent Rare Earth Ions in Sevenfold Andeightfold Coordination in Fluorite-Related Complex Oxides

“…Syntheses of Ti-containing oxides were carried out by a modified citrate method, similar to that used for BaTiO3 [ 14] and recently for Tb2Ti207 [ 15]. A stock solution of Ti 3+, Fisher Scientific SO-T-43 "Titanous Chloride Solution 20% Stabilized", was assayed gravimetrically by weighing aliquots, precipitating titanium quantitatively with NH3(aq), centrifuging, washing, and calcining to TiO2.…”