Developments in Ceramic Materials Research

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276 S. Ardizzone, C. L. Bianchi, G. Cappelletti et al. Results in Figure 10 confirm that the blue colour is solely due to V 4+ species. The role of the mineralizer can be considered to be that of stabilizing the tetravalent state of vanadium, assisting the charge balance in the zircon lattice. From the diffuse reflectance spectra L*, a* and b* parameters have been calculated. The obtained data are reported in Figure 11. While the sample V0.1 without the mineralizer is green (b* small and positive), in the presence of all the mineralizers, except for KF and KCl, the b* parameter is large and negative. The lowest values of b*, corresponding to best development of the blue colour, are obtained with NaF and LiF as the mineralizers. The lower L* value of NaF indicates that the colour is more intense. The large and positive b* values for samples added with potassium salts indicate that the samples show an intense (large L*) yellow colour. CONCLUSION Pr-, V-, and Fe-doped zircon pigments were prepared by combining a sol-gel reaction with calcinations steps in the range 600-1200°C. Investigations of the structural features of the calcined products show that all the three metals promote the formation of the zircon lattice at lower temperatures with respect to the un-promoted samples. The three metals show different promoting effects on the formation of the ZrSiO4 structure at all temperatures. The promotion sequence, V>Fe>Pr, follows, inversely, the sequence of the ionic radius of the metal ions. In order to interpret this effect the localization of the metals in the zircon lattice must be discussed. In the case of V-doped pigments the addition of the guest metal was shown to provoke an expansion of the zircon lattice. This expansion is referred to the substitution of a smaller ion with a bigger ion. Considering the present three guest metal ions it can be observed that the size of V 4+ is the closest one to that of Si in the tetrahedral sites and that the size of the ions increase progressively in passing from V to Pr. The present results allow therefore to draw two different conclusions with respect to this point. First, the sequence is to be related primarily to the matching between the size of the guest metal and that of the species in the lattice; second since the size of Zr in the lattice is much larger than that of Si, the above reported sequence apparently shows that for all the three metals the promoting effect is related to the occupation by the guest ion of the tetrahedral Si 4+ positions. The colour properties of the three groups of pigments differ not only intrinsically due to the different colours but also with respect to the colour dependence on the metal content of the samples. The colour of the V-doped samples is invariably green, and in no case assumes the desired blue shade. Apparently there is no direct relation, at least in the case of V-ZrSiO4, between the formation of the zircon structure and the development of the blue colour. To promote the blue colour mineralizers (monovalent salts) must be added to the mixture. The presence of alkaline metals (Li, Na, K) both as fluorides and as chlorides provokes important variations in the structural and optical features of the pigments. The promotion of the zircon structure follows the order Li>Na>K. In the case of the presence of Li salts zircon forms, to significant extents, even at 600°C. However the most intense blue colour of the pigment is not obtained in the presence of Li salts but by addition of NaF. The low intensity of the blue colour of the Li-promoted pigments is interpreted, on the grounds of XPS
Coloured ZrSiO4 Ceramic Pigments 277 determinations, as due to the competition between Li and V for the reticular positions in the zircon lattice. ACKNOWLEDGEMENT Financial support from the Ministry of Education, University and Research (MIUR, FIRST Funds) is gratefully acknowledged. REFERENCES [1] Eppler, RA. Resistance of porcelain enamels to attack by aqueous media: II, Equations to predict enamel durability. Am. Ceram. Soc. Bull., 1977 56(12), 1068-1070. [2] Tartaj, P; Serna, CJ; Soria, J; Ocana, M. Origin of color in aerosol-derived vanadiumdoped zirconia pigments. J. Mater. Res., 1998 13(2), 413-420. [3] Ocana, M; Caballero, A; Gonzalez-Elipe, AR; Tartaj, P; Serna, CJ; Merino, RI. The effects of the NaF flux on the oxidation state and localization of praseodymium in Prdoped zircon pigments. J. Europ. Ceram. Soc., 1999 19(5), 641-648. [4] Tartaj, P; Gonzalez-Carrno, T; Serna, CJ; Ocana, M. Iron zircon pigments prepared by pyrolysis of aerosols. J. Solid State Chem., 1997 128(1), 102-108. [5] Llusar, M; Calbo, J; Badenes, JA; Tena, MA; Monros, G. Synthesis of iron zircon coral by coprecipitation routes. J. Mater. Sci., 2001 36(1), 153-163. [6] Badenes, JA; Vicent, JB; Llusar, M; Tena, MA; Monros, G. The nature of Pr-ZrSiO4 yellow ceramic pigment. J. Mater. Sci., 2002 37(7), 1413-1420. [7] Berry, FJ; Jadon, D; Holloway, J; Smart, LE. Iron-doped zirconium silicate. Part 1. The location of iron. J. Mater. Sci., 1996 6(2), 221-225. [8] Berry, FJ; Eadon, D; Holloway, J; Smart, LE. Iron-doped zircon: the mechanism of formation. J. Mater. Sci., 1999 34(15), 3631-3638. [9] Carreto, E; Pina, C; Arriola, H; Barahona, C; Nava, N; Castano, V. Mossbauer study of the structure of Fe-zircon system. J. Radioanal. Nucl. Chem., 2001 250(3), 453-458. [10] Airey, AC; Roberts, W. Advances in ceramic colors. Ceram. Eng. Sci. Proc., 1987 8(11-12), 1168-1175. [11] Llusar, M; Badenes, JA; Calbo, J; Tena, MA; Monros, G. Environmental and colour optimisation of mineraliser addition in synthesis of iron zircon ceramic pigment. Brit. Ceram. Trans., 2000 99(1), 14-22. [12] Eppler, RA. Kinetics of formation of an iron-zircon pink color. J. Am. Ceram. Soc., 1979 62, 47-49. [13] Li, CH; Eppler, DR; Eppler, RA. Iron zircon pigments. Ceram. Eng. Sci. Proc., 1992 13(1-2), 109-118. [14] Shoyama, M; Nasu, H; Kamiya, K. Preparation of rare earth-zircon pigments by the solgel method. J. Ceram. Soc. Jap., Int. Edition 1998 106, 279-284. [15] Ocana, M; Caballero, A; Gonzalez-Elipe, AR; Tartaj, P; Serna, CJ. Valence and localization of praseodymium in Pr-doped zircon. J. Solid State Chem., 1998 139(2), 412-415.
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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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82 Photon counts 300 250 200 150 10
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84 Fluorescence, a.u. I transfer ,
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86 ln(I transfer (t)) -4.2 -4.4 -4.
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88 Fluorescence, a.u. I transfer ,
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In: Developments in Ceramic Materia
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Synthesis, Spectroscopic and Magnet
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a c Synthesis, Spectroscopic and Ma
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Transmission Transmission Transmiss
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Sm (J/Kmol) Sm (J/Kmol) 15 10 5 Syn
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Intensity (a.u.) Intensity (a.u.) 8
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The Use of Ceramic Pots in Old Wors
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3.2. Wall-in Positions The Use of C
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IACC ( τ ) = t2 ∫ The Use of Cer
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where σ res is the scattering cros
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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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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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Page 260 and 261: 246 Li Chen The continuing evolutio
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Page 305 and 306: time, vii, ix, 1, 3, 7, 8, 11, 26,
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