The effects of Y2O3 addition on the phase K-Ras(G12C) inhibitor 6 and crystal growth behavior of YSZ nanocrystals prepared via coprecipitation process have been investigated. Results indicate that tetragonal phase can be stabilized to higher temperatures as the content of Y2O3 increases. For the samples with 7% or 8% content of Y2O3, the martensitic transformation temperature increases to 1000 or 1200 °C. The average crystallite size increases with the heat-treatment temperature. For instance, the crystallite sizes of samples 3YSZ, 5YSZ, 7YSZ, 8YSZ increases from 12.35, 12.61, 11.47, 11.30 to 43.10, 50.75, 45.06, 48.22 nm with heat-treatment temperature increasing from 400 to 1200 °C, respectively. Moreover, the rate of crystal growth at low temperatures (<800 °C) is much smaller than that at higher temperatures (>800 °C). Due to different growth mechanisms, the activation energy for crystal growth in the low temperature zone is much lower than that in the high temperature zone. The activation energies of 3YSZ, 5YSZ, 7YSZ and 8YSZ nanoparticles are found to be 7.65, 5.72, 5.57 and 5.76 kJ/mol at low temperatures, respectively. However, the corresponding activation energies abruptly increase to 25.34, 32.16, 32.76 and 34.30 kJ/mol at higher temperatures, respectively.