Pyrochlore-type compounds containing double oxides of trivalent and tetravalent ions

Abstract

A study has been mad e by X-ray diffract ion analyses of t he A20 3 :2B02-type double oxides. It was found that many of t hese mixed oxides, after appropriate heat treatment, formed compounds of the formula type A2B20 7• Most of these compounds crystallized in the cubic system with a face-centered cell similar to that found for the mineral pyrochlore, although some were distorted from the ideal cubic struct ure.Ind exed X-ray diffraction powder patterns are given for t he cubic compounds 811l203· 2Ti02, Gd 20 3·2 t i02, Dy20 3·2TiOz, Y20 3·2Ti02, Ybz0 3·2TiOz, La20 3·28n02, Nd20 3· 28n02, La20 3·2Zr02, Nd20 3·2Zr02, and for the possible compounds Y20 3·2Zr02 and Nd20 3· 2UOz. Unindexed patterns are given for La20 3· 2Ti02, Nd20 3· 2Ti02 and Biz0 3·2Sn02. On the basis of the existence of the two compounds La20 3· 2Zr02 and Nd20 3·2Zr02, the phase diagrams for the systems La20 a-Zr02 and Nd20 3-Zr02 have been revised .

Structural and magnetic investigations of single-crystalline neodymium zirconate pyrochloreNd2Zr2O7

“…Analysis of the room-temperature x-ray diffraction data collected on the powder used to prepare the feed rods showed that the calculated value of the lattice parameter (a = 10.682 87(5)Å) is, in this case, very similar to that reported in the literature [29,37].…”

“…Studies of the magnetic properties have shown that the Pr 3+ ions in Pr 2 Zr 2 O 7 have a ground-state doublet with a local Ising anisotropy along 111 axes and are coupled by an antiferromagnetic exchange, but no long-range magnetic order is observed down to very low temperatures (76 mK) [21,24,25]. The spin ice-like correlations revealed by elastic magnetic neutron scattering, the broad excitation spectrum observed in the low-energy inelastic neutron scattering, and the reduction of the nuclear contribution to the heat capacity [24] may be connected with the strongly anisotropic superexchange and multipolar interactions [26,27] • C, although the melting point was not established [29]. The order-to-disorder transition in Nd 2 O 3 -ZrO 2 occurs at 2300…”

Magnetocaloric study of spin relaxation in dipolar spin iceDy2Ti2O7

“…Polycrystalline powdered samples of Dy 2 Ti 2 O 7 and (DyY)Ti 2 O 7 were prepared using well established solidstate synthesis techniques 29 . The Y 3+ ion was used for magnetic dilution since it has nearly the same ionic radius as Dy 3+ .…”

High‐Temperature Stable Zirconia Particles Doped with Yttrium, Lanthanum, and Gadolinium

“…The diffraction refl exes for La 2 Zr 2 O 7 were no longer observed after reheating (see Supporting Information Figure S20), suggesting redissolution of the La 2 Zr 2 O 7 into the monoclinic phase. The La concentrations for the particles (3% and less) are borderline with the range for solid solubility in monoclinic zirconia, as given by the phase diagrams for the La 2 O 3 -ZrO 2 system, [22][23][24] but are higher than maximum solubility of 1% La reported by Bastide et al [ 21 ] Lastly, after heating at 1500 °C, all samples were fully sintered and had lost their spherical shape, as shown in the Supporting Information ( Figure S4). …”

“…[21][22][23][24] La 2 Zr 2 O 7 and Gd 2 Zr 2 O 7 have been considered for TBC applications due to their high melting points, phase stabilities, and low thermal conductivities. However, their use is impeded by a low toughness compared to YSZ [ 25 ] and a thermal expansion mismatch between the coating and metallic layer in the components.…”