PDF Publication Title:
Text from PDF Page: 007
Condens. Matter 2019, 4, 86 7 of 15 3.2. Mössbauer Spectroscopy of LiFePO4 Mössbauer spectra were collected and evaluated for three different experimental conditions varying in temperature and external magnetic field: (i) T = 60 K (> TN), Bext = 0 T; (ii) T = 4.2 K (< TN), Bext = 0 T; and (iii) T = 4.2 K (< TN), Bext = 6 T. The fitted parameters of the spectra are shown in Table 1 and discussed in detail below. The overall observation is that theory—as discussed in more detail the subsequent section—underestimates the Vzz and η parameters and overestimates Bhf (when only the Fermi contact interaction contributes to Bhf). Table 1. The hyperfine parameters determined from the 57Fe Mössbauer spectra in LiFePO4 for the three experiments performed. I stands for the intensity of spectral components. Underlined numbers represent the mean values of corresponding quantities. In the case of Bhf (Bext = 6 T), the value is in fact the mean value of Beff. Whereas for Bext = 0 T (T = 4.2 K), it is not necessary to consider the value as an average since the distribution width is very small. Spectrum Type D O O T Bext Bhf (K) (T) (T) Vzz (1021 V/m2 ) – 16.7 16.7 η φ (◦ ) – – 0.77(1) 0 0.78(1) ∼143 IS QS I Γ (mm/s) (mm/s) (%) (mm/s) 60 0 – 4.2 0 12.4(2) 1.35(2) 3.05(2) 100 0.29(1) 4.2 6 12.7(2) 1.35(2) 3.04(2) 100 0.29(1) θ ∆Beff (◦ ) (T) – – 0 ∼0.3 ∼13 ∼6 1.33(2) 3.01(2) 100 0.30(1) The 57Fe Mössbauer spectrum of LiFePO4 above the Néel temperature at temperature T = 60 K, see Figure 5, was fitted with a symmetrical, Lorentzian-shaped quadrupole doublet D. The doublet D with reasonably narrow line widths Γ = 0.30(1) mm/s, quadrupole splitting QS = 3.02(2) mm/s and isomer shift IS = 1.33(2) mm/s (in agreement with work [16]), see Table 1, was assigned to ferrous Fe2+ ions in the high spin state S = 2 [15,37]. At temperature T = 4.2 K the 57Fe Mössbauer spectrum was fitted with one octet O (eight absorption lines [38]) with a narrow distribution of Bhf in the static Hamiltonian (see Figure 6). The octet component O with Bhf = 12.4(2) T, QS = 3.05(2) mm/s, and IS = 1.35(2) mm/s were ascribed, similarly to the doublet D at T = 60 K, to Fe2+ ions with the high spin state S = 2. The orientation of Bhf on 57Fe nuclei is antiparallel to the orientation of the magnetic moment of Fe2+ ions (like in pure iron), which is parallel to the crystallographic direction [010] [10]. The principal axis of the EFG main component Vzz = 16.7(1) × 1021 V/m2, with respect to the zero polar angle θ ∼ 0◦, see Table 1, is collinear with the direction [010], which is expectable in some respect (because of the Fe site symmetry, one principal EFG axis should be parallel with this direction). At the Fe2+ sites, due to a non-zero value of the asymmetry parameter η ∼ 0.8, there is no ordinary local symmetry axis, except the normal to the mirror plane (i.e., C1h point symmetry).PDF Image | Mossbauer Spectroscopy of Triphylite (LiFePO4) at Low Temperatures
PDF Search Title:
Mossbauer Spectroscopy of Triphylite (LiFePO4) at Low TemperaturesOriginal File Name Searched:
condensedmatter-04-00086.pdfDIY PDF Search: Google It | Yahoo | Bing
Sulfur Deposition on Carbon Nanofibers using Supercritical CO2 Sulfur Deposition on Carbon Nanofibers using Supercritical CO2. Gamma sulfur also known as mother of pearl sulfur and nacreous sulfur... More Info
CO2 Organic Rankine Cycle Experimenter Platform The supercritical CO2 phase change system is both a heat pump and organic rankine cycle which can be used for those purposes and as a supercritical extractor for advanced subcritical and supercritical extraction technology. Uses include producing nanoparticles, precious metal CO2 extraction, lithium battery recycling, and other applications... More Info
CONTACT TEL: 608-238-6001 Email: greg@infinityturbine.com (Standard Web Page)