Synthesis and Thermophysical Properties of (La1-xMgx)2Ce2O7-x

doi:10.15541/jim20140144

Abstract

Abstract:

Doping magnesium into La₂Ce₂O₇ can increase its thermal expansion coefficient (TEC) and decrease its thermal conductivity (TC), thus improve its performance for thermal barrier coating (TBC). (La_1-_xMg_x)₂Ce₂O_7-_x ceramics were prepared by Sol-Gel method. Powder X-Ray diffraction results revealed that (La_1-_xMg_x)₂Ce₂O_7-_x showed the identical structure as La₂Ce₂O₇ (defect-fluorite type), and the crystal parameter decrease with increasing x value in the range of 0≤x≤0.4, and MgO occurred in the product when x?0.4. The TEC of (La_1-_xMg_x)₂Ce₂O_7-_x sample (0≤x≤0.4) with the same composition increases with the increasing temperature, whereas the TC presents the opposite trend. At the same temperature, the TEC of the (La_1-_xMg_x)₂Ce₂O_7-_x sample (0≤x≤0.4) with different composition increases with increasing x value whereas the TC increases firstly and then decreases with the increasing of x value, where x=0.2 nearby as turning point. In addition, possible mechanisms of the influence of Mg doping on the structure, crystal parameter, TEC and TC of La₂Ce₂O₇ are discussed.

Key words: La2Ce2O7, magnesium-doped, thermal expansion coefficient, thermal conductivity, thermal barrier coating ceramic

CLC Number:

O641

YANG Bin, LI Lin-Yan, FAN Min-Guang, LI Bin, XU Sheng-Ming, WANG Jian-Long, LIN Xu-Ping. Synthesis and Thermophysical Properties of (La_1-_xMg_x)₂Ce₂O_7-_x[J]. Journal of Inorganic Materials, 2014, 29(12): 1301-1305.

Figures/Tables 8

Fig. 1 XRD patterns of the Mg2+-doped La2Ce2O7 products ((La1-xMgx)2Ce2O7-x) synthesized by Sol-Gel method

Fig. 2 Mg2+-doping dependence of the crystal parameter (a) of (La1-xMgx)2Ce2O7-x

Fig. 3 Change of the thermal expansion coefficient (TEC) of (La1-xMgx)2Ce2O7-x with temperature

Table 1 Measured and theoretical density of (La1-xMgx)2Ce2O7-x

x	0	0.1	0.2	0.3	0.4
ρ/(g·cm^-3)	5.79	6.05	6.02	5.76	5.44
ρ₀/(g·cm^-3)	6.43	6.23	6.02	5.82	5.60

Fig. 4 Change of the specific heat capacity of (La1-xMgx)2Ce2O7-x with temperature

Fig. 5 Change of the thermal diffusivities of (La1-xMgx)2Ce2O7-x with temperature

Fig. 6 Change of the thermal conductivity of (La1-xMgx)2Ce2O7-x with temperature

Fig. 7 Composition dependence of the thermal conductivity for (La1-xMgx)2Ce2O7-x at 1000oC

References 24

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Synthesis and Thermophysical Properties of (La_1-_xMg_x)₂Ce₂O_7-_x

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