The estimation parameter of nanoceramics crystalline structure deviation from thermodynamically equilibrium state

摘要

Using XRD techniques the correlations of the relative crystallite microstrains (RCM) with apparent crystallite sizes (ACS) for zirconia ceramic nanopowders, their green compacts pressed under different power of ultrasound action, and nanostructured ceramics sintered from them at various temperatures were analyzed. It was shown, that for all the samples the RCM values are inversely proportional to magnitudes of ACS with proportionality coefficient k, which is constant with high precision for the same material in equilibrium state. Physically coefficient k is a value of ACS actual change /spl Delta/d/sub ACS/ under microstresses action of crystallite having the certain defective substructure in a material existing in a stable state. The equation for coefficient k as a quantity of actual change of the ACS under microstrains action was offered. The difference between the coefficient k for ceramics sintered at lower temperatures and its statistical average value for ceramics sintered at optimal temperature reflects a deviation degree of the examined matter structure from thermodynamically equilibrium state. This deviation can be an estimation parameter of ceramics processing efficiency or compliance of technological conditions with optimal ones. The modulus of | k /spl Delta/d/sub ACS/ | was minimal for the structural zirconia ceramics sintered at optimum temperature and having the maximum mechanical characteristics.