Phase transitions in monoclinic ZrO-=SUB=-2-=/SUB=-

Zirconia ZrO 2 is one of the most important modern materials, but its use faces problem complex polymorphism. It generally accepted that, under normal conditions, it exists in monoclinic form P2_1/c (N 14), which undergoes an extended martensitic transformation into tetragonal P4_2/nmc 137) when heated above 1000 o C. However, group-theoretic analysis forbids a direct transition between these space groups and requires at least two intermediate forms. The experiment carried out this work using structure-sensitive methods (dilatometry electrical conductivity) indeed revealed existence singular points on temperature dependences expansion conductivity range 350±20 730±20 This agrees with literature data, demonstrate lattice parameters. According to dilatometry transitions are phase second order, correlates obtained Raman data (measurements temperatures up 900 C 60-900 cm -1 ), showing that local structure changes slightly, therefore, occur within framework syngony. Keywords: , phases, transitions, dilatometry, conductivity, spectroscopy.