Properties of YBaCuFe1 ? xNixO5 (0 < x ? 0.3) solid solutions

Abstract

YBaCuFe 1x Ni x O 5 solid solutions are shown to exist for x ≤ 0.3. Data are presented on the lattice parameters, thermal stability, thermal expansion, electrical conductivity, thermoelectric power, magnetic susceptibility, and dielectric properties of the solid solutions. Ni substitution for Fe notably increases the electrical conductivity of the solid solutions, reduces their thermoelectric power and thermal expansion, and shifts the antiferromagnetic-paramagnetic phase transition and dielectric anomalies in YBaCuFe 1x Ni x O 5 to lower temperatures.

The Polar Phase of NaNbO3: A Combined Study by Powder Diffraction, Solid-State NMR, and First-Principles Calculations

“…For this reason high-resolution NMR techniques such as multiple-quantum MAS (MQMAS) are required to fully remove inhomogeneous second-order quadrupolar broadenings and resolve distinct sites. The 23 Na triple-quantum MAS spectrum of NaNbO 3 , shown in Figure b, clearly displays two distinct Na resonances, in agreement with the reported crystal structure for Pbcm NaNbO 3 . The projection of the spectrum onto the δ 1 axis also exhibits two sharp isotropic peaks, again highlighting the presence of two distinct Na environments.…”

“…Initial investigations concentrated on NaNbO 3 purchased commercially (Sigma-Aldrich). Structure and phase purity were initially verified using l-PXRD and then s-PXRD, both of which displayed excellent agreement with the orthorhombic structure reported in the literature ( Pbcm ) . The Rietveld refinement using the s-PXRD data is shown in Figure a, and full refinement details can be found in Supporting Information.…”

“…The high-resolution diffraction data collected for Solid-State Sample A were analyzed in significant detail, and single phase refinements were completed for both data sets using the Pbcm model (refined lattice parameter values are located in Supporting Information). It was immediately apparent in both data sets that a single model was insufficient owing to considerable discrepancies between the theoretical model and experimental data.…”

93Nb NMR and DFT investigation of the polymorphs of NaNbO3

“…In particular, in recent years the piezoelectric responses of materials from the K x Na 1Àx NbO 3 (or KNN) solid solution have generated much interest, with the possibility of utilising such materials as lead-free alternatives to the most widely used piezoelectric material Pb(Zr x Ti 1Àx )O 3 or PZT. 3,4 While the structure of KNbO 3 is well determined (space group Amm2), 5 the structure of NaNbO 3 is more widely debated, [6][7][8][9][10][11][12][13][14][15][16][17] with a series of poorly understood phase transitions proposed with varying temperature. Even at room temperature a number of different structural variations have been suggested, the most common of which is the orthorhombic Pbcm phase.…”