Abstract
We report the sol–gel synthesis of Cu2V2O7 fine particles, in which some of the constituent Cu is replaced with other elements. The sintered body of Zn substituted β-Cu1.8Zn0.2V2O7 shows a large negative thermal expansion (NTE) over a wide temperature range due to microstructural effects peculiar to a ceramic body. Using the sol–gel method, we successfully produced β-Cu1.8Zn0.2V2O7 ceramic fine particles that retain the same level of thermal expansion suppression capabilities as the bulk with a size of about 1 μm. We also succeeded in performing rare earth metal (Ce, Sm, Yb) substitutions, which might be a clue for improving NTE performance. These achievements provide particulate filler for thermal expansion control of a micrometer region, which has been earnestly sought in many fields of technology.
Highlights
Controlling thermal expansion has become an important issue in modern industry, and there is a strong demand for negative thermal expansion (NTE) materials that have excellent thermal expansion control capabilities
In the case of NTE resulting from microstructural effects, as in the present system, there is a risk that the microstructures relevant to NTE might be destroyed if pulverized
Of the variable temperature x-ray diffraction (XRD) at 300 K–400 K obtained by synchrotron radiation
Summary
Materials such as manganese nitrides, bismuth–nickel oxides, and lead–vanadium oxides have been found to exhibit a large NTE due to a volume change accompanying the phase transition. Such phase-change type NTE materials exhibit large negative linear expansion coefficients α. The microstructural effects are a result of the anisotropic thermal deformation of the crystal lattice and have fewer restrictions on the operating T range. By doping Cu2V2O721–25 with Zn, the obtained β-Cu1.8Zn0.2V2O7 showed a large NTE with the linear thermal expansion coefficient α = −14.4 ppm/K over a wide T range of 100 K–700 K.26. In order to reduce the particle size, it is necessary to “make it small from the beginning.”
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