Developments in Ceramic Materials Research

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132 José M. Rojo, José L. Mesa and Teófilo Rojo The thermal dependence of the ordered magnetic moments is represented in Figure 29(b). The Mx refined magnetic component is always higher than that of the Mz one. At 7.5 K, near the ordering temperature, the ratio Mx/Mz is 2.0. Below 6 K the Mz component undergoes a slight change reaching saturation at 3.5 K. However, the Mx moment continuously increases up to 1.5 K (Mx/Mz = 2.5). This feature does not cause any change in the magnetic structure, but only a slight spin reorientation at low temperature. Figure 28. Projection of the magnetic structures in the (010) plane of (a) Mo(PO 3) 3 (where dashed lined represents the Ia unit cell) and (b) Fe(PO 3) 3. The directions of the electronic spins and the fundamental unit cells in the Cc space group are shown for comparison. Figure 29 (Continued). (a)
Synthesis, Spectroscopic and Magnetic Studies… 133 (b) Figure 29. Thermal evolution of (a) neutron diffraction patterns, and (b) the ordered magnetic moments [M, Mx and Mz] for the Fe(PO3) 3compound. On the other hand, the neutron diffraction patterns do not show any atypical thermal evolution at temperatures less than TN = 8 K. Consequently, the magnetic anomalies observed in the specific heat study can not be attributed to the presence of magnetic transitions. 8. MAGNETO-STRUCTURAL CORRELATIONS The magnetic interactions in the B and C chromium metaphosphates and iron and molybdenum ones are only propagated via (PO4) tetrahedra (Cr-O-P-O-Cr) and can be described as super-superexchange [58] interactions owing to the exchange M-O-M interactions are absent in all the compounds. The super-superexchange magnetic couplings are always antiferromagnetic and are characterized by both the O-P-O angles and the M-O bond lengths. The shorter metal-metal distances range between 5.0 and 6.2 Å (see Table 4) and consequently direct interactions are negligible. The magnetic exchanges are more effective for the shorter M-O distances and for an angle near 109° (tetrahedral angle) [51]. For these compounds, the metal-oxygen distances are approximately 2.0 Å and the O-P-O angles are quite different (110-120°) from those of tetrahedral geometry. In this sense, the weak antiferromagnetic interactions observed in both chromium compounds are a consequence of the large distances between the M(III) ions and the open angles in the M-O-P- O-M pathways. Schematic views of the most important exchange pathways in the B and C chromium types metaphosphates are given in Figure 30. For Cr(PO3)3, [see Figure 30(a)] the chromiumchromium interactions principally occur through one and two (PO4) groups. Nine exchange
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DEVELOPMENTS IN CERAMIC MATERIALS R
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Copyright © 2007 by Nova Science P
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PREFACE Ceramics are refractory, in
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Preface ix crystals is discussed. A
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Preface xi spectra and the directio
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2 Leslie G. Cecil comprehensive dat
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4 Leslie G. Cecil Ringle et al. (19
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6 Leslie G. Cecil The main architec
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8 Leslie G. Cecil can study “the
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10 Leslie G. Cecil Middleton et al.
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12 Leslie G. Cecil The laser ablate
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14 Leslie G. Cecil There are two ge
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16 Leslie G. Cecil distinct recipes
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18 Leslie G. Cecil second group (Fi
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20 Leslie G. Cecil The Vitzil-Orang
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22 Leslie G. Cecil Table 3. Mahalan
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24 Leslie G. Cecil Ixlú and Ch’i
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26 Leslie G. Cecil structures (D. R
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28 Leslie G. Cecil paste and Macanc
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30 Leslie G. Cecil Bieber, A. M. Jr
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32 Leslie G. Cecil Kepecs, S. M., a
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34 Leslie G. Cecil Schele, L., Grub
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36 Z. C. Li, Z. J. Pei and C. Tread
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54 T. T. Basiev, V. A. Demidenko, K
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62 I, % 100 80 60 40 20 0 T. T. Bas
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68 Fluorescence, a.u. 1 T. T. Basie
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70 Fluorescence, a.u. 1 0.1 0.01 0.
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78 k, cm -1 20 18 16 14 12 10 8 6 4
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Page 111 and 112: In: Developments in Ceramic Materia
Page 113 and 114: Synthesis, Spectroscopic and Magnet
Page 115 and 116: a c Synthesis, Spectroscopic and Ma
Page 119 and 120: Transmission Transmission Transmiss
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Page 179 and 180: D50 0.8 0.7 0.6 0.5 0.4 0.3 The Use
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Modeling of Thermal Transport in Ce
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q x = Modeling of Thermal Transport
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212 R. Ramesh, H. Kara, Ron Stevens
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220 ε S 33 R. Ramesh, H. Kara, Ron
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242 Development of Display Technolo
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244 Li Chen technology moved to the
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246 Li Chen The continuing evolutio
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248 Li Chen the back contact cathod
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250 Li Chen Figure 3. Vertical side
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252 Li Chen Figure 6. Molybdenum mi
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254 Li Chen Figure 8(a). I-V curve
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256 Li Chen Figure 9. Life time tes
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258 Figure 11(a). Plasma generated
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260 Li Chen [13] C.A. Spindt, K.R.
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262 S. Ardizzone, C. L. Bianchi, G.
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A absorption spectra, 66, 67, 77, 7
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correlation function, 156 corrosion
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group membership, 13, 20, 21, 22, 2
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microstructure(s), x, xi, 73, 74, 2
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efraction index, 61 refractive inde
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time, vii, ix, 1, 3, 7, 8, 11, 26,
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Developments in Ceramic Materials Research

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