Coherent effects in regular three-dimensional lattices of insulator nanocrystals in an opal matrix

Samples of the nanocomposite opal +NaCl with 100% filling of first-order vo ids in the opal by NaCl have been obtained. The thermal conductivity of the nanocomposite has been measured in the temperature interval 4.2-300 K. It is shown that NaCl, introduced into opal, forms a regular "matrix quasilatt ice'' of microcrystals, which leads to suppression of coherent effects and, as a consequence, of properties characteristic of massive crystals. (C) 19 99 American Institute of Physics. [S1063-7834(99)03002-6].