Negative thermal expansion material of yttrium molybdate has been synthesized by rapid solidification with a CO 2 laser. It crystallized in the orthorhombic phase with unique microstructures consisting of nanoparticles or nanodendrites with grain sizes around 20-30 nm. Raman spectroscopic and XRD analyses reveal that the presence of water species hinders not only the rocking motion but every type of motion of the corner shared polyhedra. Because of the presence of water species, degeneracy of the Raman bands happens for symmetric stretching, asymmetric stretching, and the bending modes, and the lattice, translational, and librational modes cannot be observed. The release of water species below 403 K (388 K for the newly prepared sample or 383 K in the second temperature cycle) has little whereas that above this temperature has great effect on the stretching and bending vibrations and also the librational and translational modes. This indicates that the water species which are released within the first step do not interact with the MoO 4 tetrahedra in the Y 2 -Mo 3 O 12 framework while those released in the second step have a direct interaction. It is suggested that the translational and librational motions are closely coupled with stretching and bending vibrations. They together give rise to the negative thermal expansion.

Paper, as one of the most important inventions of mankind, is still widely used in our daily life. In this study, the paper is explored as a platform for power sources based on the universally known triboelectric friction. A novel paper triboelectric nanogenerator (P-TENG) was successfully developed, which could harvest mechanical energy from ambient sources and generate considerable electrical energy. The maximum power density of the P-TENG reached 53 W m. In addition, the P-TENG possesses a natural advantage of being able to be integrated within a book, and thus can effectively convert mechanical energy from the action of turning book pages into electricity. When turning a book page, the output voltage and current of the P-TENG were obtained to be about 400 V and 0.17 mA, respectively. This generated electricity could directly light up 80 commercial white light-emitting diodes (LEDs) connected in series without any energy storage process. The white LEDs powered by the P-TENG can provide sufficient illumination for reading printed text in darkness. This research provides a promising solution for developing paper-based self-powered electronic systems.

Ce(3+) ions are introduced into the lattice of Y2Mo3O12 with a sol-gel method with the aim to reduce its hygroscopicity and pursue the interaction of crystal water molecules with the building block. It is found that Ce(3+) ions occupy the positions of Y(3+) in the lattice and have the function of expelling crystal water molecules in the microchannels so that the number of crystal water molecules decreases significantly as the Ce(3+) content increases and a complete depletion of the crystal water is achieved when the content of Ce(3+) is higher than 8 mol%. Based on the binding energy changes of Mo 3d and Y 3d with and without Ce(3+) in the lattice, the configuration of the crystal water in the building block is deduced, namely, a crystal water serves as a spring with its O(2-) pointing to the Y(3+) in an octahedron and with its H(+) approaching the next nearest O(2-) in the Y-O-Mo bridge. With such a configuration, the effects of the crystal water on the thermal expansion properties of Y2Mo3O12 and the like are explained. It is also shown that the number of crystal water molecules per molecular formula can be quantified by the full width at half maximum of the Raman bands or relative intensity with linear relationships, suggesting that Raman spectroscopy can be a potential tool in quantifying crystal water molecules at room temperature in this or related materials.

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