Developments in Ceramic Materials Research

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114 José M. Rojo, José L. Mesa and Teófilo Rojo can be concluded that the molybdenum metaphosphate is well described as a threedimensional Heisenberg antiferromagnet with a J/k value ca. 0.4 K. Figure 11. Thermal variation of χ m and χ mT product for Mo(PO 3) 3. Figure 12. Thermal variation of χm for Cr(PO 3) 3 [(a), open circle] and Cr 2(P 6O 18) [(b), black circle]. Inset shows the thermal evolution of χm for the Cr 2(P 6O 18) compound at different magnetic fields (open circle, 10 mT; blac circle, 100 mT; +, 1T]. The magnetic behavior of Cr(PO3)3 is very similar to that exhibited by the homologous molybdenum compound. The susceptibility vs. temperature curve shows a maximum at 4.5 K
Synthesis, Spectroscopic and Magnetic Studies… 115 (Figure 12a), obeying the Curie-Weiss law with Cm= 1.83 cm 3 Kmol -1 and θ= -2.7. Considering the analogies between both compounds, from the structural and electronic point of view, this result is not surprising. The most important difference is observed for the Curie constant, which exhibits higher values for the chromium than for the molybdenum compound. This fact results from the effect of the spin-orbit coupling which is less important for an element of the first transition series such as chromium. Consequently, a lower deviation from the free-electron g value and a higher Cm value are observed in this case. A simple treatment as was described above for the molybdenum metaphosphate allows us to conclude that the Cr(PO3)3 phase orders as a three-dimensional Heisenberg antiferromagnet with a J/k value of ca. 0.3 K. The magnetic behavior of the Cr2(P6O18) hexametaphosphate is substantially different from that observed for the chromium metaphosphate. The χm vs. T curve does not exhibit any appreciable anomaly at applied magnetic fields > 1T (Figure 12b). The high-temperature data follow a Curie-Weiss law with Cm= 1.83 cm 3 Kmol -1 and θ= -0.2 K. The value of the Curie constant is practically the same as that observed for Cr(PO3)3. This result is in good agreement with the similar environment observed for the Cr(III) ions and the negligible influence of the magnetic interactions above 50 K for both compounds. The magnetic effective moment measured under an applied magnetic field of 0.1 T decreases from 3.82 μB at room temperature to 3.09 μB at 1.8 K, showing the existence of antiferromagnetic interactions in the compound. χm as a function of temperature at lower applied magnetic fields rise below ca. 3 K indicating a magnetic transition (inset in Figure 12). A very sharp peak in – d(χT)/dT vs. T provides a more accurate ordering temperature of TN= 2.2 K. Magnetization as a function of applied field at below and above TN is shown in Figure 13. The linear increase of the magnetization above 0.1 T and the absence of saturation behavior up to 7 T imply and antiferromagnetic-like ordering. Figure 13. Magnetization vs. applied magnetic field, beloww (open circle) and above (black circle) TN for the Cr2(P 6O 18) compound.
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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 111 and 112: In: Developments in Ceramic Materia
Page 113 and 114: Synthesis, Spectroscopic and Magnet
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Page 137 and 138: Sm (J/Kmol) Sm (J/Kmol) 15 10 5 Syn
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D50 0.8 0.7 0.6 0.5 0.4 0.3 The Use
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Definition (D50) 1 0.95 0.9 0.85 0.
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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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