負熱膨張性微粒子の開発.

Because of growing demands for thermal expansion control in a local region, typically inner components of electronic devices, there is currently a great deal of interest in negative thermal expansion (NTE) fine particles. The spray-drying method without grinding produced micrometer-scale fine particles of pyrovanadate Cu_1.8Zn_0.2V₂O₇ showing a large negative coefficient of linear thermal expansion α_L ~ –14 ppm/K equivalent to that of the bulk body. The solid-solution system Cu_1.8Zn_0.2V_2–xP_xO₇ maintains the NTE functionality in a wide x compositional range. Phosphorus substitution contributes to cost reduction and to improvement of electrical insulation. Control of the structural phase transition in the phosphate analog Zn₂P₂O₇ by substituting Mg for Zn realized a huge negative α_L exceeding –60 ppm/K over a wide temperature range including room temperature. Because small particles are obtainable even with the conventional solid-phase reaction, the 1 μm level fine particles were obtained successfully using the pulverization method without degrading the function. It has high practicality because it is composed only of inexpensive and environmentally friendly elements such as Zn, Mg, and P. These NTE fine particles are expected to support great progress in thermal expansion control engineering. [ABSTRACT FROM AUTHOR]