Size effect of the thermal expansion of nanostructural copper oxide

The temperature dependence of the thermal expansion Delta L/L of samples of high-density nanostructural CuO ceramics with a crystallite size of 20, 70, and 90 nm was measured. The nanoceramics were obtained from coarse-grained CuO powders under converging spherical shock waves. It is found that, at temperatures T > 50 K, the thermal expansion coefficient alpha(T) of the nanoceramic samples increases with decreasing crystallite sizes and exceeds the value of alpha(T) of the CuO single crystal by a factor of 3.5 to 4.5. At temperatures T < 50 K, regions with zero and negative values of alpha(T) were revealed. The possible reasons for the increase in the thermal expansion coefficient of nanoceramics based on 3d-metal oxides are discussed.