“…The tetragonality of the 50 h milled nanopowder seems to be slightly bigger than expected on the base of the paper [13]. This suggests that the critical value of PbTiO 3 particle size can be smaller the predicted in [13]; however, the accuracy of the lattice parameters determination for the nanograins is smaller due to the broadening of characteristic reflections and the c/a ratio can depend on the degree of imperfection of cationic and anionic sublattices of PbTiO 3 [15].…”
Section: Resultsmentioning
confidence: 64%
“…It should be also stressed that a size-driven tetragonal-cubic phase transition has been observed in ferroelectric perovskites (BaTiO 3 and PbTiO 3 ) [10][11][12][13][14][15][16]. It was found for particles below 200 nm the degree of tetragonality increases with increasing crystallite size.…”
Lead titanate nanopowders were fabricated by mechanochemical synthesis from lead oxide and titanium dioxide. The milling process has been carefully investigated by X-ray diffraction and X-ray excited photoelectron spectroscopy. The first traces of perovskite phase were detected after 5 h synthesis. It was found that intermediated phases (Ti 10 O 18 and Pb 3 O 4 ) have been formed at the early stage of synthesis. The 50 h milling results in single perovskite phase with average crystallite size of 20 nm.
“…The tetragonality of the 50 h milled nanopowder seems to be slightly bigger than expected on the base of the paper [13]. This suggests that the critical value of PbTiO 3 particle size can be smaller the predicted in [13]; however, the accuracy of the lattice parameters determination for the nanograins is smaller due to the broadening of characteristic reflections and the c/a ratio can depend on the degree of imperfection of cationic and anionic sublattices of PbTiO 3 [15].…”
Section: Resultsmentioning
confidence: 64%
“…It should be also stressed that a size-driven tetragonal-cubic phase transition has been observed in ferroelectric perovskites (BaTiO 3 and PbTiO 3 ) [10][11][12][13][14][15][16]. It was found for particles below 200 nm the degree of tetragonality increases with increasing crystallite size.…”
Lead titanate nanopowders were fabricated by mechanochemical synthesis from lead oxide and titanium dioxide. The milling process has been carefully investigated by X-ray diffraction and X-ray excited photoelectron spectroscopy. The first traces of perovskite phase were detected after 5 h synthesis. It was found that intermediated phases (Ti 10 O 18 and Pb 3 O 4 ) have been formed at the early stage of synthesis. The 50 h milling results in single perovskite phase with average crystallite size of 20 nm.
“…We recommend that one acquires spectra with small spikelet separation in such cases. It would be interesting to see if the very small orthorhombic distortions of PbTiO 3 , recently detected in powder X-ray work 71,72 and unlikely detectable via classic NMR experiments, could be detected with the modified-CPMG experiment at low temperatures. 69 Lead zirconate, PbZrO 3 , is one of the rare lead compounds having two nonequivalent Pb sites and seems to be an excellent candidate for examining the utility of the modified-CPMG method for a sample with multiple sites.…”
Section: Resultsmentioning
confidence: 99%
“…We recommend that one acquires spectra with small spikelet separation in such cases. It would be interesting to see if the very small orthorhombic distortions of PbTiO 3 , recently detected in powder X-ray work , and unlikely detectable via classic NMR experiments, could be detected with the modified-CPMG experiment at low temperatures 5 6 Comparison of experimental and calculated 207 Pb NMR spectra of PbTiO 3 at 7.05 T. (a) Experimental spectrum corresponding to Figure c; (b) optimum simulated spectrum using the chemical-shift parameters given in Table . …”
The utility of the Carr-Purcell Meiboom-Gill (CPMG) experiment and a modified-CPMG experiment in characterizing NMR chemical-shift powder patterns for spin-1 / 2 nuclei is demonstrated. Heavier NMR-active nuclei such as 195 Pt, 199 Hg, and 207 Pb are known to be extremely sensitive to their local environment and as such have very large chemical-shift ranges. In the solid state, such nuclei commonly exhibit chemical shifts that range well over 1000 ppm, depending upon the orientation of the molecule within the applied magnetic field. Thus, acquiring NMR spectra of polycrystalline samples is often an experimental challenge because of these very broad powder patterns. In acquiring chemical-shift powder patterns of these nuclei, we provide several examples that demonstrate that a considerable saving in time is realized by using the CPMG experiment as opposed to the standard one-pulse or spin-echo experiment. In general, this time saving is even greater if a modified-CPMG experiment is used. Homonuclear dipolar interactions are considerably reduced in the CPMG experiment and are almost completely removed in the modified-CPMG experiment. For samples containing 1 H, larger enhancements are realized by combining the CPMG experiment with cross polarization. By use of the CPMG and the modified-CPMG experiments, the principal components of the chemical-shift tensors are determined for each of the samples studied.
Ab initio high-throughput materials screening of inorganic perovskites yields candidates for applications in photovoltaics, ferroelectrics, magnetoelectrics, and as transparent contacts.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
