Ca-PSZ prepared via polymeric sol–gel route

Microstructural control of 10 mol% Ca-PSZ through doping and heat treatment was studied after firing at 1300, 1400 and 1500°C/2 h using SEM. Tetragonal precipitate was developed under a condition of metastability and transformed partially to monoclinic in the presence of stresses developed through nucleation and growth when the particle size became above the critical grain size. The volume of critically metastable t-precipitate was maximized to more than 90% through controlling transformation between 1300 and 1400°C/2 h. The average grain size of the major phase is related to the precipitation conditions, where t-ZrO2 precipitate prevents abnormal grain growth and swallows pores. Combined with submicron size microstructure, closed packing without any signs of pores exists without applied stress at 1400°C/2 h. Controlled chemical preparation via polymerization reaction of urea with formaldehyde forming polyamide resin was utilized for preparation of very fine nanomaterials with narrow particle size distribution. Metal cations are homogeneously distributed through the structure of the resin. The conditions achieved lead to the precipitation of tetragonal zirconia without grain growth or crack formation.