Developments in Ceramic Materials Research

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118 José M. Rojo, José L. Mesa and Teófilo Rojo Figure 16. Thermal dependence of the χ mT product and 1/ χm for Fe(PO 3) 3. The negative Weiss temperature and the observed decrease in the χmT product with decreasing temperature (Figure 16) are indicative of the existence of antiferromagnetic exchanges as major interactions in this compound. Considering the structural features of the Fe(PO3)3 compound superexchange interactions via (PO4) tetrahedra can only be expected. Despite the complexity of the three-dimensional arrangement a simple cubic network can be considered to be an acceptable description of the stacking of the iron(III) ions and can be utilized to obtain an approximate value of the exchange parameter. Considering the usual isotropic magnetic behavior of the Fe(III) cations, a Heisenberg Hamiltonian can be proposed as a theoretical approach to the magnetic behavior. The best fit of the experimental data was obtained for g= 2.00 and J/k= -0.36 K, and it is represented by the solid line in Figure 16. Despite the differences between the real system and the employed model, the calculated curve follows the experimental data rather well. Moreover, for such a system a sharp maximum in the thermal evolution of the magnetic susceptibility is expected at 8.5 K, in good agreement with the experimental data. Therefore, it can be concluded that the magnetic behavior of the iron(III) metaphosphate is well described as a three-dimensional Heisenberg antiferromagnetic with a J/k value about 0.4 K. 6.5. Specific Heat Measurements of the M(PO3)3 (M= Cr, Fe, Mo) Metaphosphates The specific-heat measurements of the M(PO3)3 (M= Cr, Fe and Mo) metaphosphates between 1.8 and 35 K are shown in Figures 17 and 18 [48,49]. The heat capacity data exhibit three-dimensional magnetic ordering peaks at 4.2, 4 and 7.8 K for Cr, Fe and Mo phases, respectively. The temperatures at which these λ-type peaks appear are similar to those obtained from the magnetic susceptibility measurements (T = 4.5, 4.5 and 8.0 K for Cr, Fe and Mo metaphosphates, respectively).
Synthesis, Spectroscopic and Magnetic Studies… 119 Figure 17. Specific heat (Cp) of Cr(PO 3) 3. Cl and Cm are the estimated lattice and magnetic contributions, respectively. Inset shows the heat capacity of Cr(PO3) 3 in the neighbourhood of the ordering temperature. The solid lines correspond to the T T N equations. Figure 18. (Continued)
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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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Page 113 and 114: Synthesis, Spectroscopic and Magnet
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The Use of Ceramic Pots in Old Wors
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The Use of Ceramic Pots in Old Wors
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In: Developments in Ceramic Materia
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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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