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Effect of isovalent substitution on phase transition and negative thermal expansion of In2−xScxW3O12 ceramics
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CERAMICS INTERNATIONAL
Ceramics International ] (]]]]) ]]]–]]] www.elsevier.com/locate/ceramint
Effect of isovalent substitution on phase transition and negative thermal expansion of In2 xScxW3O12 ceramics Hongfei Liua,n, Zhiping Zhangb, Jian Maa, Zhu Juna, Xianghua Zenga a School of Physics Science and Technology, Yang zhou University, Yang zhou 225002, PR China Department of Electrical and Mechanical Engineering, Guangling College, Yang zhou University, Yang zhou 225002, PR China
b
Received 16 March 2015; received in revised form 1 April 2015; accepted 13 April 2015
Abstract Solid solutions of In2 xScxW3O12 (0 rx r 2) were successfully synthesized using the solid state reaction method. Effects of substituted scandium content on the phase composition, microstructure, phase transition temperatures and thermal expansion behaviors of the resulting In2 xScxW3O12 (0 r x r2) samples were investigated using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and thermal mechanical analyzer (TMA). Results indicate that the obtained In2W3O12 ceramic undergoes a structure phase transition from monoclinic to orthorhombic at 248 1C. This phase transition temperature of In2W3O12 can be easily shifted to a lower temperature by partly substituting the In3 þ with Sc3 þ . When the x value increased from 0 to 1, the phase transition temperatures of In2 xScxW3O12 (0 rx r 2) samples decreased from 248 to 47 1C. All the In2 xScxW3O12 (0 r x r 2) ceramics show fine negative thermal expansion below their corresponding phase transition temperatures. The negative thermal expansion coefficients of the In2 xScxW3O12 (0 rx r 2) ceramics change in the range from 1.08 10 6 1C 1 to 7.13 10 6 1C 1. & 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Keywords: Ceramics; Phase transition; Negative thermal expansion; Tungstates
1. Introduction Recently, negative thermal expansion (NTE) materials have attracted widespread interests due to their potential applications in micro-electrical, optical and high-temperature devices. This property is observed in some molybdates and tungstates of general formula A2M3O12, where A cation could be any trivalent transition metal or rare earth element, and M is mainly Mo6 þ or W6 þ [1–5]. The structure of the family A2M3O12 compounds consists of a network of corner sharing AO6 octahedra and MO4 tetrahedra. A–O–W linkages in their structure can accommodate transverse thermal vibrations and lead to the NTE. Many members of the A2M3O12 family show a reversible phase transition from monoclinic to orthorhombic symmetry with increasing temperatures [6–10]. n
Corresponding author. Tel.: þ86 514 87975466; fax: þ 86 514 87975467. E-mail address: [email protected] (H. Liu).
In2W3O12, a member of A2M3O12 family, is reported to exhibit structural phase transition at about Tc=523 K. Several investigations on the thermal expansion behavior of In2W3O12 have been reported using the X-ray diffraction measurement and dilatometer. X-ray diffraction shows that the structure of In2W3O12 below Tc is monoclinic with the space group P21/a, and above Tc is orthorhombic with the space group Pnca. Both the X-ray diffraction and dilatometric measurements indicated In2W3O12 showed a positive thermal expansion below Tc and its average linear thermal expansion coefficient was about 20 10 6 K 1, while it showed NTE above Tc and its average linear thermal expansion coefficient was about 3.0 10 6 K 1 [11–13]. This abrupt change from positive-to-negative thermal expansion in In2W3O12 is disadvantageous for potential applications if the phase transition temperature (Tc) is within the working temperature range. Thus it is important to shift the phase transition temperature to room temperature or moved out of the practical working range of the materials.
http://dx.doi.org/10.1016/j.ceramint.2015.04.062 0272-8842/& 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Please cite this article as: H. Liu, et al., Effect of isovalent substitution on phase transition and negative thermal expansion of In2 xScxW3O12 ceramics, Ceramics International (2015), http://dx.doi.org/10.1016/j.ceramint.2015.04.062
2
H. Liu et al. / Ceramics International ] (]]]]) ]]]–]]]
In this work, we attempt to modulate the phase transition temperature by isovalent substitution of the In3 þ site in the octahedral with Sc3 þ . The effects of substituted scandium content on the phase composition, microstructure, phase transition and Table 1 Lattice parameters of the In2 xScxW3O12 (x¼ 0, 0.1, 0.3, 0.5, 1, and 2) ceramics.
Fig. 1. XRD patterns of the obtained In2 xScxW3O12 (x ¼0, 0.1, 0.3, 0.5, 1, and 2) ceramics (a) In2W3O12; (b) In1.9Sc0.1W3O12; (c) In1.7Sc0.3W3O12; (d) In1.5Sc0.5W3O12; (e) InScW3O12; and (f) Sc 2W3O12.
Samples
a (Å)
b (Å)
c (Å)
In2W3O12 In1.9Sc0.1W3O12 In1.7Sc0.3W3O12 In1.5Sc0.5W3O12 InScW3O12 Sc2W3O12
16.3685 16.3634 16.3619 16.3614 16.3471 13.3289
9.6473 9.6459 9.6451 9.6390 9.6325 9.5873
19.0454 19.0342 19.0315 19.0283 19.0259 9.6791
Fig. 2. Cross-sectional SEM images of the obtained In2 xScxW3O12 (x¼ 0, 0.1, 0.3, 0.5, 1, and 2) ceramics (a) In2W3O12; (b) In1.9Sc0.1W3O12; (c) In1.7Sc0.3W3O12; (d) In1.5Sc0.5W3O12; (e) InScW3O12; and (f) Sc2W3O12.
Please cite this article as: H. Liu, et al., Effect of isovalent substitution on phase transition and negative thermal expansion of In2 xScxW3O12 ceramics, Ceramics International (2015), http://dx.doi.org/10.1016/j.ceramint.2015.04.062
H. Liu et al. / Ceramics International ] (]]]]) ]]]–]]]
thermal expansion behaviors of the In2 xScxW3O12 (0rxr2) ceramics were studied. 2. Experimental The samples of In2 xScxW3O12 ceramics were synthesized using the conventional solid state reaction method. Starting materials were In2O3 (purityZ99.99% metals basis), Sc2O3 (purityZ99.99% metals basis) and WO3 (purityZ99.99% metals basis) powders. Stoichiometric ratios of the reactants were milled for 12 h to form a uniform mixture and then pre-calcined at 700 1C for 10 h. After pre-sintering, the mixtures were uniaxially cold pressed into pellets which were 10 mm in diameter and about 3 mm in thickness, then finally calcined respectively at 1050 1C in air for 12 h and cooled down in the furnace. Structural characterization was carried out using an XRD (Shimadzu XRD-7000) with CuKα radiation. Data were collected at 40 kV and 200 mA, with scanning speed of 51/min over an angular range of 10–601. The cross section morphologies of the samples were observed using a field emission scanning electron microscopy (FESEM, Hitachi S4800). The thermal expansion coefficients of the samples were measured using a thermal mechanical analysis (TMA/SS, Seiko 6300). The measurements were carried out with a heating rate of 10 1C/min in air from room temperature to 700 1C. 3. Results and discussion Fig. 1 shows the typical XRD patterns of the obtained In2 xScxW3O12 (x¼ 0, 0.1, 0.3, 0.5, 1, and 2) ceramics. In Fig. 1(a), all the observed diffraction peaks can be well indexed to a monoclinic crystal structure In2Mo3O12 (JCPDS Card no. 74-1791), and the In2W3O12 is isostructural to In2Mo3O12. It indicates the In2W3O12 crystalizes in monoclinic crystal structure at ambient temperature, which is also in good agreement with the reported literatures [11–13]. In Fig. 1(b)–(f), The In2 xScxW3O12 (x¼ 0.1, 0.3, 0.5, and 1) samples synthesized with different amounts of scandium have almost the same XRD patterns with In2W3O12, which indicates the In2 xScxW3O12 (x¼ 0.1, 0.3, 0.5, and 1) ceramics show monoclinic crystal structures at ambient temperature and a single phase can be formed due to the relatively small differences in their cationic radii of In3 þ (0.8 Å) and Sc3 þ (0.745 Å). In Fig. 1(f), all the observed diffraction peaks could be well indexed to orthorhombic phase Sc2W3O12 (JCPDS Card no. 21-1065). The lattice constants of the In2 xScxW3O12 (x ¼ 0.1, 0.3, 0.5, and 1) ceramics synthesized with different amounts of substituted scandium were calculated by the cell parameter calculation method using the Powder X software [14,15], which was shown in Table 1. It indicates that the a, b and caxes cell parameters decrease gradually with the increase of the substituted Sc3 þ content owing to that the ionic radii of Sc3 þ (0.745 Å) is smaller than that of In3 þ (0.8 Å). This is in good agreement with the Vegard's law. On the other hand, it proves that the solid solutions of In2 xScxW3O12 (x¼ 0.1, 0.3, 0.5, and 1) compounds have been successfully synthesized.
3
Cross-sectional FESEM images of the obtained In2 xScxW3O12 (x ¼ 0, 0.1, 0.3, 0.5, 1, and 2) ceramics are shown in Fig. 2. It can be seen that the In2W3O12 ceramic comprises uniform grains and some pores. The grain shapes are similar and the average grain size is about 2–6 μm (Fig. 2(a)). The Sc2W3O12 ceramic shows a more compact density compared to In2W3O12 ceramic (Fig. 2(f)). Crosssectional morphologies of the In2 xScxW3O12 (x¼ 0.1, and 0.3) ceramics are almost the same (Fig. 2(b) and (f)), but the grain shapes show a less uniform compared to In2W3O12 ceramic. When the x value increased to 0.5, the In1.5Sc0.5W3O12 ceramic become denser. The grain shapes of the In1Sc1W3O12 ceramic are similar to the ones of In2W3O12 ceramic, but the average grain size become smaller and which is about 1–4 μm. It also can be seen that each sample of the obtained In2 xScxW3O12 (x ¼ 0, 0.1, 0.3, 0.5, 1, and 2) ceramics comprise the same shape grains, indicating the the solid solution In2 xScxW3O12 (x¼ 0, 0.1, 0.3, 0.5, 1, and 2) compounds have been successfully synthesized. Fig. 3 shows the thermal expansion curves of the obtained In2 xScxW3O12 (x¼ 0, 0.1, 0.3, 0.5, 1, and 2) ceramics. In Fig. 3(a), the slope of the thermal expansion curve for In2W3O12 ceramic changes in the temperature range from 248 to 277 1C, indicating the In2W3O12 undergoes a structure phase transition from monoclinic to orthorhombic. The monoclinic In2W3O12 ceramic shows positive thermal expansion, and the thermal expansion coefficient is measured to be 16.51 10 6 K 1 in the temperature range from 27 to 248 1C. The orthorhombic In2W3O12 ceramic shows NTE, and the thermal expansion coefficient is measured to be 3.0 10 6 K 1 in the temperature range from 277 to
Fig. 3. Thermal expansion curves of the obtained In2 xScxW3O12 (x¼ 0, 0.1, 0.3, 0.5, 1, and 2) ceramics (a) In2W3O12; (b) In1.9Sc0.1W3O12; (c) In1.7Sc0.3W3O12; (d) In1.5Sc0.5W3O12; (e) InScW3O12; and (f) Sc2W3O12.
Please cite this article as: H. Liu, et al., Effect of isovalent substitution on phase transition and negative thermal expansion of In2 xScxW3O12 ceramics, Ceramics International (2015), http://dx.doi.org/10.1016/j.ceramint.2015.04.062
H. Liu et al. / Ceramics International ] (]]]]) ]]]–]]]
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Table 2 Average linear thermal expansion coefficients of the In2 xScxW3O12 (x ¼0, 0.1, 0.3, 0.5, 1, and 2) ceramics in corresponding testing temperature range. Samples
NTE coefficients ( 10 6 1C 1)
Testing temperature range (1C)
NTE coefficients ( 10 6 1C 1)
Testing temperature range (1C)
In2W3O12 In1.9Sc0.1W3O12 In1.7Sc0.3W3O12 In1.5Sc0.5W3O12 InScW3O12 Sc2W3O12
16.51 17.02 13.22 17.12 – –
27–248 25–224 25–214 25–147 – –
3.00 5.29 1.08 1.28 7.13 2.84
277.0–700 250.6–700 235.2–700 160.5–700 58.4–700 26.0–700
700 1C, which are in close agreement with the values reported earlier [11–13]. This phase transition leads to a remarkable deviation from the linear temperature dependence of the expansion coefficient from 16.51 10 6 K 1 to 3.0 10 6 K 1. However, as the increase of the substituted scandium, the phase transition temperature gradually shifts to the lower temperatures. When the x value increased to 1, the phase transition temperature for the solid solution InScW3O12 decreased from 248 to 47 1C. The major factor influencing the temperature form the monoclinic to orthorhombic phase transition is the electronegativity of the A3 þ cation. Evans et al. has reported that the lager electronegativity of the A3 þ cation is, the higher the phase transition temperature of the A2W3O12 will be [3]. In this reversible phase transition process, no strong bonds are formed or broken; the framework connectivity remains unchanged. Only a volume changed caused by oxygen–oxygen attraction, and the electronegativity of the A3 þ cation has a significant effect on the oxygen– oxygen attraction. The electronegativity of the Sc3 þ cation is less than the one of In3 þ , with the increase of the substituted Sc3 þ , the electronegativity of the (In2 xScx)3 þ decreases. Thus, it causes the phase transition to occur at lower temperatures. It also can be seen that the thermal expansion curve of the obtained orthorombic InScW3O12 ceramic is straight slash, indicating that the InScW3O12 ceramic shows a stable NTE with the increase of temperatures. Meanwhile, there is no visible change in slope of the thermal expansion curve for Sc2W3O12 in the testing temperature range from 26 to 700 1C (Fig. 3(f)). The monoclinic to orthorhombic phase transition in Sc2W3O12 is reported to occur at about 263 1C [7,16]. Table 2 shows the average linear thermal expansion coefficients of the obtained orthorhombic In2 xScxW3O12 (x¼ 0, 0.1, 0.3, 0.5, 1, and 2) ceramics in corresponding testing temperature range. Meanwhile, the average linear thermal expansion coefficients of the In2 xScxW3O12 (x ¼ 0, 0.1, 0.3, 0.5, 1, and 2) ceramics below the corresponding phase transition temperature are also given in Table 2. 4. Conclusions Solid solutions In2 xScxW3O12 (0rxr2) were prepared using the conventional solid state reaction method. All the In2 xScxW3O12 (0rxr2) ceramics synthesized with different
amounts of scandium show single phase. The monocline to orthorhombic structural phase transition temperature of the In2W3O12 can be shift to lower temperature by partly substituting the In3 þ cation with Sc3 þ cation. The phase transition temperature for the InScW3O12 is 47 1C, and it show a stable NTE in the temperature range from 47 to 700 1C, which will have more potential applications in many fields. Acknowledgments The authors thank the National Natural Science Foundation of China (Nos. 51102207 and 11475145), University Natural Science Research Foundation of Jiangsu Province (14KJB430025), Yangzhou University Science and Technique Innovation Foundation (No. 2010CXJ081). References [1] S. Sumithra, A.M. Umarji, Role of crystal structure on the thermal expansion of Ln2W3O12 (Ln ¼La, Nd, Dy, Y, Er and Yb), Solid State Sci. 6 (2004) 1313–1319. [2] S. Sumithra, A.M. Umarji, Negative thermal expansion in rare earth molybdates, Solid State Sci. 8 (2006) 1453–1458. [3] J.S.O. Evans, T.A. Mary, A.W. Sleight, Negative thermal expansion in a large molybdate and tungstate family, J. Solid State Chem. 133 (1997) 580–583. [4] H.F. Liu, W. Zhang, Z.P. Zhang, X.B. Chen, Synthesis and negative thermal expansion properties of solid solutions Yb2 xLaxW3O12 (0 rx r2), Ceram. Int. 38 (2012) 2951–2956. [5] S. Sumithra, A.K. Tyagi, A.M. Umarji, Negative thermal expansion in Er2W3O12 and Yb2W3O12 by high temperature X-ray diffraction, Mater. Sci. Eng. B 116 (2005) 14–18. [6] M.M. Wu, J. Peng, S.B. Han, Z.B. Hu, Y.T. Liu, D.F. Chen, Phase transition and negative thermal expansion properties of Sc2 xCrxMo3O12, Ceram. Int. 38 (2012) 6525–6529. [7] Q.Q. Liu, J. Yang, X.N. Cheng, G.S. Liang, X.J. Sun, Preparation and characterization of negative thermal expansion Sc2W3O12/Cu core–shell composite, Ceram. Int. 38 (2012) 541–545. [8] J.S.O. Evans, T.A. Mary, Structural phase transitions and negative thermal expansion in Sc2(MoO4)3, Int. J. Inorg. Mater. 2 (2000) 143–151. [9] B.A. Marinkovic, M. Ari, P.M. Jardim, R.R. de Avillez, F. Rizzo, F. F. Ferreira, In2Mo3O12: a low negative thermal expansion compound, Thermochim. Acta 499 (2010) 48–53. [10] M. Ari, P.M. Jardim, B.A. Marinkovic, F. Rizzo, F.F. Ferreira, Thermal expansion of Cr2xFe2 2xMo3O12, Al2xFe2 2xMo3O12 and Al2xCr2 2xMo3O12 solid solutions, J. Solid State Chem. 181 (2008) 1472–1479. [11] V. Sivasubramanian, T.R. Ravindran, R. Nithya, A.K. Arora, Structural phase transition in indium tungstate, J. Appl. Phys. 96 (2004) 387–392.
Please cite this article as: H. Liu, et al., Effect of isovalent substitution on phase transition and negative thermal expansion of In2 xScxW3O12 ceramics, Ceramics International (2015), http://dx.doi.org/10.1016/j.ceramint.2015.04.062
H. Liu et al. / Ceramics International ] (]]]]) ]]]–]]] [12] M. Maczka, K. Hermanowicz, J. Hanuza, Phase transition and vibrational properties of A2(BO4)3 compounds (A¼ Sc, In; B ¼Mo, W), J. Mol. Struct. 744–747 (2005) 283–288. [13] T.I. Baiz, C.P. Heinrich, N.A. Banek, B.L. Vivekens, C. Lind, In-situ non-ambient X-ray diffraction studies of indium tungstate, J. Solid State Chem. 187 (2012) 195–199. [14] H.F. Liu, Z.P. Zhang, W. Zhang, X.B. Chen, Negative thermal expansion ZrW2O8 thin films prepared by pulsed laser deposition, Surf. Coat. Technol. 205 (2011) 5073–5076.
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[15] X.J. Sun, J. Yang, Q.Q. Liu, X.N. Cheng, Influence of sodium dodecyl benzene sulfonate (SDBS) on the morphology and negative thermal expansion property of ZrW2O8 powders synthesized by hydrothermal method, J. Alloys Compd. 481 (2009) 668–672. [16] J.S.O. Evans, T.A. Mary, A.W. Sleight, Negative thermal expansion in Sc2(WO4)3, J. Solid State Chem. 137 (1998) 148–160.
Please cite this article as: H. Liu, et al., Effect of isovalent substitution on phase transition and negative thermal expansion of In2 xScxW3O12 ceramics, Ceramics International (2015), http://dx.doi.org/10.1016/j.ceramint.2015.04.062
CERAMICS INTERNATIONAL
Ceramics International ] (]]]]) ]]]–]]] www.elsevier.com/locate/ceramint
Effect of isovalent substitution on phase transition and negative thermal expansion of In2 xScxW3O12 ceramics Hongfei Liua,n, Zhiping Zhangb, Jian Maa, Zhu Juna, Xianghua Zenga a School of Physics Science and Technology, Yang zhou University, Yang zhou 225002, PR China Department of Electrical and Mechanical Engineering, Guangling College, Yang zhou University, Yang zhou 225002, PR China
b
Received 16 March 2015; received in revised form 1 April 2015; accepted 13 April 2015
Abstract Solid solutions of In2 xScxW3O12 (0 rx r 2) were successfully synthesized using the solid state reaction method. Effects of substituted scandium content on the phase composition, microstructure, phase transition temperatures and thermal expansion behaviors of the resulting In2 xScxW3O12 (0 r x r2) samples were investigated using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and thermal mechanical analyzer (TMA). Results indicate that the obtained In2W3O12 ceramic undergoes a structure phase transition from monoclinic to orthorhombic at 248 1C. This phase transition temperature of In2W3O12 can be easily shifted to a lower temperature by partly substituting the In3 þ with Sc3 þ . When the x value increased from 0 to 1, the phase transition temperatures of In2 xScxW3O12 (0 rx r 2) samples decreased from 248 to 47 1C. All the In2 xScxW3O12 (0 r x r 2) ceramics show fine negative thermal expansion below their corresponding phase transition temperatures. The negative thermal expansion coefficients of the In2 xScxW3O12 (0 rx r 2) ceramics change in the range from 1.08 10 6 1C 1 to 7.13 10 6 1C 1. & 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Keywords: Ceramics; Phase transition; Negative thermal expansion; Tungstates
1. Introduction Recently, negative thermal expansion (NTE) materials have attracted widespread interests due to their potential applications in micro-electrical, optical and high-temperature devices. This property is observed in some molybdates and tungstates of general formula A2M3O12, where A cation could be any trivalent transition metal or rare earth element, and M is mainly Mo6 þ or W6 þ [1–5]. The structure of the family A2M3O12 compounds consists of a network of corner sharing AO6 octahedra and MO4 tetrahedra. A–O–W linkages in their structure can accommodate transverse thermal vibrations and lead to the NTE. Many members of the A2M3O12 family show a reversible phase transition from monoclinic to orthorhombic symmetry with increasing temperatures [6–10]. n
Corresponding author. Tel.: þ86 514 87975466; fax: þ 86 514 87975467. E-mail address: [email protected] (H. Liu).
In2W3O12, a member of A2M3O12 family, is reported to exhibit structural phase transition at about Tc=523 K. Several investigations on the thermal expansion behavior of In2W3O12 have been reported using the X-ray diffraction measurement and dilatometer. X-ray diffraction shows that the structure of In2W3O12 below Tc is monoclinic with the space group P21/a, and above Tc is orthorhombic with the space group Pnca. Both the X-ray diffraction and dilatometric measurements indicated In2W3O12 showed a positive thermal expansion below Tc and its average linear thermal expansion coefficient was about 20 10 6 K 1, while it showed NTE above Tc and its average linear thermal expansion coefficient was about 3.0 10 6 K 1 [11–13]. This abrupt change from positive-to-negative thermal expansion in In2W3O12 is disadvantageous for potential applications if the phase transition temperature (Tc) is within the working temperature range. Thus it is important to shift the phase transition temperature to room temperature or moved out of the practical working range of the materials.
http://dx.doi.org/10.1016/j.ceramint.2015.04.062 0272-8842/& 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
Please cite this article as: H. Liu, et al., Effect of isovalent substitution on phase transition and negative thermal expansion of In2 xScxW3O12 ceramics, Ceramics International (2015), http://dx.doi.org/10.1016/j.ceramint.2015.04.062
2
H. Liu et al. / Ceramics International ] (]]]]) ]]]–]]]
In this work, we attempt to modulate the phase transition temperature by isovalent substitution of the In3 þ site in the octahedral with Sc3 þ . The effects of substituted scandium content on the phase composition, microstructure, phase transition and Table 1 Lattice parameters of the In2 xScxW3O12 (x¼ 0, 0.1, 0.3, 0.5, 1, and 2) ceramics.
Fig. 1. XRD patterns of the obtained In2 xScxW3O12 (x ¼0, 0.1, 0.3, 0.5, 1, and 2) ceramics (a) In2W3O12; (b) In1.9Sc0.1W3O12; (c) In1.7Sc0.3W3O12; (d) In1.5Sc0.5W3O12; (e) InScW3O12; and (f) Sc 2W3O12.
Samples
a (Å)
b (Å)
c (Å)
In2W3O12 In1.9Sc0.1W3O12 In1.7Sc0.3W3O12 In1.5Sc0.5W3O12 InScW3O12 Sc2W3O12
16.3685 16.3634 16.3619 16.3614 16.3471 13.3289
9.6473 9.6459 9.6451 9.6390 9.6325 9.5873
19.0454 19.0342 19.0315 19.0283 19.0259 9.6791
Fig. 2. Cross-sectional SEM images of the obtained In2 xScxW3O12 (x¼ 0, 0.1, 0.3, 0.5, 1, and 2) ceramics (a) In2W3O12; (b) In1.9Sc0.1W3O12; (c) In1.7Sc0.3W3O12; (d) In1.5Sc0.5W3O12; (e) InScW3O12; and (f) Sc2W3O12.
Please cite this article as: H. Liu, et al., Effect of isovalent substitution on phase transition and negative thermal expansion of In2 xScxW3O12 ceramics, Ceramics International (2015), http://dx.doi.org/10.1016/j.ceramint.2015.04.062
H. Liu et al. / Ceramics International ] (]]]]) ]]]–]]]
thermal expansion behaviors of the In2 xScxW3O12 (0rxr2) ceramics were studied. 2. Experimental The samples of In2 xScxW3O12 ceramics were synthesized using the conventional solid state reaction method. Starting materials were In2O3 (purityZ99.99% metals basis), Sc2O3 (purityZ99.99% metals basis) and WO3 (purityZ99.99% metals basis) powders. Stoichiometric ratios of the reactants were milled for 12 h to form a uniform mixture and then pre-calcined at 700 1C for 10 h. After pre-sintering, the mixtures were uniaxially cold pressed into pellets which were 10 mm in diameter and about 3 mm in thickness, then finally calcined respectively at 1050 1C in air for 12 h and cooled down in the furnace. Structural characterization was carried out using an XRD (Shimadzu XRD-7000) with CuKα radiation. Data were collected at 40 kV and 200 mA, with scanning speed of 51/min over an angular range of 10–601. The cross section morphologies of the samples were observed using a field emission scanning electron microscopy (FESEM, Hitachi S4800). The thermal expansion coefficients of the samples were measured using a thermal mechanical analysis (TMA/SS, Seiko 6300). The measurements were carried out with a heating rate of 10 1C/min in air from room temperature to 700 1C. 3. Results and discussion Fig. 1 shows the typical XRD patterns of the obtained In2 xScxW3O12 (x¼ 0, 0.1, 0.3, 0.5, 1, and 2) ceramics. In Fig. 1(a), all the observed diffraction peaks can be well indexed to a monoclinic crystal structure In2Mo3O12 (JCPDS Card no. 74-1791), and the In2W3O12 is isostructural to In2Mo3O12. It indicates the In2W3O12 crystalizes in monoclinic crystal structure at ambient temperature, which is also in good agreement with the reported literatures [11–13]. In Fig. 1(b)–(f), The In2 xScxW3O12 (x¼ 0.1, 0.3, 0.5, and 1) samples synthesized with different amounts of scandium have almost the same XRD patterns with In2W3O12, which indicates the In2 xScxW3O12 (x¼ 0.1, 0.3, 0.5, and 1) ceramics show monoclinic crystal structures at ambient temperature and a single phase can be formed due to the relatively small differences in their cationic radii of In3 þ (0.8 Å) and Sc3 þ (0.745 Å). In Fig. 1(f), all the observed diffraction peaks could be well indexed to orthorhombic phase Sc2W3O12 (JCPDS Card no. 21-1065). The lattice constants of the In2 xScxW3O12 (x ¼ 0.1, 0.3, 0.5, and 1) ceramics synthesized with different amounts of substituted scandium were calculated by the cell parameter calculation method using the Powder X software [14,15], which was shown in Table 1. It indicates that the a, b and caxes cell parameters decrease gradually with the increase of the substituted Sc3 þ content owing to that the ionic radii of Sc3 þ (0.745 Å) is smaller than that of In3 þ (0.8 Å). This is in good agreement with the Vegard's law. On the other hand, it proves that the solid solutions of In2 xScxW3O12 (x¼ 0.1, 0.3, 0.5, and 1) compounds have been successfully synthesized.
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Cross-sectional FESEM images of the obtained In2 xScxW3O12 (x ¼ 0, 0.1, 0.3, 0.5, 1, and 2) ceramics are shown in Fig. 2. It can be seen that the In2W3O12 ceramic comprises uniform grains and some pores. The grain shapes are similar and the average grain size is about 2–6 μm (Fig. 2(a)). The Sc2W3O12 ceramic shows a more compact density compared to In2W3O12 ceramic (Fig. 2(f)). Crosssectional morphologies of the In2 xScxW3O12 (x¼ 0.1, and 0.3) ceramics are almost the same (Fig. 2(b) and (f)), but the grain shapes show a less uniform compared to In2W3O12 ceramic. When the x value increased to 0.5, the In1.5Sc0.5W3O12 ceramic become denser. The grain shapes of the In1Sc1W3O12 ceramic are similar to the ones of In2W3O12 ceramic, but the average grain size become smaller and which is about 1–4 μm. It also can be seen that each sample of the obtained In2 xScxW3O12 (x ¼ 0, 0.1, 0.3, 0.5, 1, and 2) ceramics comprise the same shape grains, indicating the the solid solution In2 xScxW3O12 (x¼ 0, 0.1, 0.3, 0.5, 1, and 2) compounds have been successfully synthesized. Fig. 3 shows the thermal expansion curves of the obtained In2 xScxW3O12 (x¼ 0, 0.1, 0.3, 0.5, 1, and 2) ceramics. In Fig. 3(a), the slope of the thermal expansion curve for In2W3O12 ceramic changes in the temperature range from 248 to 277 1C, indicating the In2W3O12 undergoes a structure phase transition from monoclinic to orthorhombic. The monoclinic In2W3O12 ceramic shows positive thermal expansion, and the thermal expansion coefficient is measured to be 16.51 10 6 K 1 in the temperature range from 27 to 248 1C. The orthorhombic In2W3O12 ceramic shows NTE, and the thermal expansion coefficient is measured to be 3.0 10 6 K 1 in the temperature range from 277 to
Fig. 3. Thermal expansion curves of the obtained In2 xScxW3O12 (x¼ 0, 0.1, 0.3, 0.5, 1, and 2) ceramics (a) In2W3O12; (b) In1.9Sc0.1W3O12; (c) In1.7Sc0.3W3O12; (d) In1.5Sc0.5W3O12; (e) InScW3O12; and (f) Sc2W3O12.
Please cite this article as: H. Liu, et al., Effect of isovalent substitution on phase transition and negative thermal expansion of In2 xScxW3O12 ceramics, Ceramics International (2015), http://dx.doi.org/10.1016/j.ceramint.2015.04.062
H. Liu et al. / Ceramics International ] (]]]]) ]]]–]]]
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Table 2 Average linear thermal expansion coefficients of the In2 xScxW3O12 (x ¼0, 0.1, 0.3, 0.5, 1, and 2) ceramics in corresponding testing temperature range. Samples
NTE coefficients ( 10 6 1C 1)
Testing temperature range (1C)
NTE coefficients ( 10 6 1C 1)
Testing temperature range (1C)
In2W3O12 In1.9Sc0.1W3O12 In1.7Sc0.3W3O12 In1.5Sc0.5W3O12 InScW3O12 Sc2W3O12
16.51 17.02 13.22 17.12 – –
27–248 25–224 25–214 25–147 – –
3.00 5.29 1.08 1.28 7.13 2.84
277.0–700 250.6–700 235.2–700 160.5–700 58.4–700 26.0–700
700 1C, which are in close agreement with the values reported earlier [11–13]. This phase transition leads to a remarkable deviation from the linear temperature dependence of the expansion coefficient from 16.51 10 6 K 1 to 3.0 10 6 K 1. However, as the increase of the substituted scandium, the phase transition temperature gradually shifts to the lower temperatures. When the x value increased to 1, the phase transition temperature for the solid solution InScW3O12 decreased from 248 to 47 1C. The major factor influencing the temperature form the monoclinic to orthorhombic phase transition is the electronegativity of the A3 þ cation. Evans et al. has reported that the lager electronegativity of the A3 þ cation is, the higher the phase transition temperature of the A2W3O12 will be [3]. In this reversible phase transition process, no strong bonds are formed or broken; the framework connectivity remains unchanged. Only a volume changed caused by oxygen–oxygen attraction, and the electronegativity of the A3 þ cation has a significant effect on the oxygen– oxygen attraction. The electronegativity of the Sc3 þ cation is less than the one of In3 þ , with the increase of the substituted Sc3 þ , the electronegativity of the (In2 xScx)3 þ decreases. Thus, it causes the phase transition to occur at lower temperatures. It also can be seen that the thermal expansion curve of the obtained orthorombic InScW3O12 ceramic is straight slash, indicating that the InScW3O12 ceramic shows a stable NTE with the increase of temperatures. Meanwhile, there is no visible change in slope of the thermal expansion curve for Sc2W3O12 in the testing temperature range from 26 to 700 1C (Fig. 3(f)). The monoclinic to orthorhombic phase transition in Sc2W3O12 is reported to occur at about 263 1C [7,16]. Table 2 shows the average linear thermal expansion coefficients of the obtained orthorhombic In2 xScxW3O12 (x¼ 0, 0.1, 0.3, 0.5, 1, and 2) ceramics in corresponding testing temperature range. Meanwhile, the average linear thermal expansion coefficients of the In2 xScxW3O12 (x ¼ 0, 0.1, 0.3, 0.5, 1, and 2) ceramics below the corresponding phase transition temperature are also given in Table 2. 4. Conclusions Solid solutions In2 xScxW3O12 (0rxr2) were prepared using the conventional solid state reaction method. All the In2 xScxW3O12 (0rxr2) ceramics synthesized with different
amounts of scandium show single phase. The monocline to orthorhombic structural phase transition temperature of the In2W3O12 can be shift to lower temperature by partly substituting the In3 þ cation with Sc3 þ cation. The phase transition temperature for the InScW3O12 is 47 1C, and it show a stable NTE in the temperature range from 47 to 700 1C, which will have more potential applications in many fields. Acknowledgments The authors thank the National Natural Science Foundation of China (Nos. 51102207 and 11475145), University Natural Science Research Foundation of Jiangsu Province (14KJB430025), Yangzhou University Science and Technique Innovation Foundation (No. 2010CXJ081). References [1] S. Sumithra, A.M. Umarji, Role of crystal structure on the thermal expansion of Ln2W3O12 (Ln ¼La, Nd, Dy, Y, Er and Yb), Solid State Sci. 6 (2004) 1313–1319. [2] S. Sumithra, A.M. Umarji, Negative thermal expansion in rare earth molybdates, Solid State Sci. 8 (2006) 1453–1458. [3] J.S.O. Evans, T.A. Mary, A.W. Sleight, Negative thermal expansion in a large molybdate and tungstate family, J. Solid State Chem. 133 (1997) 580–583. [4] H.F. Liu, W. Zhang, Z.P. Zhang, X.B. Chen, Synthesis and negative thermal expansion properties of solid solutions Yb2 xLaxW3O12 (0 rx r2), Ceram. Int. 38 (2012) 2951–2956. [5] S. Sumithra, A.K. Tyagi, A.M. Umarji, Negative thermal expansion in Er2W3O12 and Yb2W3O12 by high temperature X-ray diffraction, Mater. Sci. Eng. B 116 (2005) 14–18. [6] M.M. Wu, J. Peng, S.B. Han, Z.B. Hu, Y.T. Liu, D.F. Chen, Phase transition and negative thermal expansion properties of Sc2 xCrxMo3O12, Ceram. Int. 38 (2012) 6525–6529. [7] Q.Q. Liu, J. Yang, X.N. Cheng, G.S. Liang, X.J. Sun, Preparation and characterization of negative thermal expansion Sc2W3O12/Cu core–shell composite, Ceram. Int. 38 (2012) 541–545. [8] J.S.O. Evans, T.A. Mary, Structural phase transitions and negative thermal expansion in Sc2(MoO4)3, Int. J. Inorg. Mater. 2 (2000) 143–151. [9] B.A. Marinkovic, M. Ari, P.M. Jardim, R.R. de Avillez, F. Rizzo, F. F. Ferreira, In2Mo3O12: a low negative thermal expansion compound, Thermochim. Acta 499 (2010) 48–53. [10] M. Ari, P.M. Jardim, B.A. Marinkovic, F. Rizzo, F.F. Ferreira, Thermal expansion of Cr2xFe2 2xMo3O12, Al2xFe2 2xMo3O12 and Al2xCr2 2xMo3O12 solid solutions, J. Solid State Chem. 181 (2008) 1472–1479. [11] V. Sivasubramanian, T.R. Ravindran, R. Nithya, A.K. Arora, Structural phase transition in indium tungstate, J. Appl. Phys. 96 (2004) 387–392.
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Please cite this article as: H. Liu, et al., Effect of isovalent substitution on phase transition and negative thermal expansion of In2 xScxW3O12 ceramics, Ceramics International (2015), http://dx.doi.org/10.1016/j.ceramint.2015.04.062