Preparation And Properties Of Zr₂P₂WO₁₂ And Its Composites

Negative thermal expansion materials refer to the materials with negative coefficients of thermal expansion and the volume of which decreases with increasing of temperature in a certain temperature range. As one member of A2(MO4)3 family, Zr2P2WO12 has obvious negative thermal expansion properties in large range of temperature. Zr2P2WO12 is widely used in the fields of electrics, optics and medical apparatus because of its excellent performance, such as thermal and chemical stability, mechanical stability at high temperature, etc. At present, the research on Zr2P2WO12 is limited. Therefore, Zr2P2WO12 powders were prepared by hydrothermal method in this paper. The compact Fe-Ni/Zr2P2WO12 composites were successfully prepared by vacuum hot pressing sintering method. PI/ Zr2P2WO12 composites were fabricated by in-situ polymerization technique. The properties of Zr2P2WO12 and Fe-Ni/Zr2P2WO12 composites were characterized by XRD, SEM and thermal dilatometer. The hardness of the Fe-Ni/ Zr2P2WO12 composites was tested by Vickers hardness tester. The relative density of the composites was calculated by drainage method according to Archimedes technique. For PI/ Zr2P2WO12 composites fabricated by in-situ polymerization technique, the properties were characterized by Fourier transform infrared spectroscopy(FTIR), SEM, thermal analyzer, thermal dilatometer and Impedance meter. The influences of the coupling agent and Zr2P2WO12 with different content on the properties of the composites were studied. The main results are as following:1. Zr2P2WO12 powders prepared by hydrothermal method are quasi-nanometer and pure powders with monophase.2. With the increment of Zr2P2WO12 in the Fe-Ni/ Zr2P2WO12 composites, the hardness of the composites increased, while the density and the relative density reduced. The average linear coefficient of the composites reduced from 13.5×10-6 K-1 to 8.6×10-6 K-1 in the temperature range of 25℃ to 800℃.3. With the increasing of Zr2P2WO12 in the PI/Zr2P2WO12 composites, the thermal stability of the composites was enhanced, the dielectric constant increased slightly and the change of dielectric loss was not obvious. The average linear coefficient of the composites was reduced from 45.67×10-6K-1 to 30.81×10-6K-1(about 32.5% of reduction) in the temperature range of 25℃ to 350℃.