纳米ZrO_2-8%Y_2O_3粉末的相转变及晶粒生长动力学

Phase transition and grain growth kinetics of nanocrystalline 8% yttria stabilized zirconia powder

采用共沉淀法制备纳米ZrO2．8％Y203（质量分数）粉末，然后将其在大气中于1100-1300℃范围内高温煅烧处理2～32h。利用XRD、SEM、TEM等方法研究纳米ZrO2-8％Y203粉末高温煅烧前后的相成分、形貌和晶粒粒径变化，并分析纳米ZrO2-8％Y203粉末的晶粒生长动力学及生长机制。结果表明：纳米ZrO2-8％Y203经高温煅烧后，单斜相和四方相含量随温度的升高和时问的延长而减少，立方相含量随温度的升高和时间的延长而增加；随温度的升高和时间的延长晶粒粒径逐渐增大；在1250℃等温煅烧时，其晶粒生长指数为6，晶粒生长速率常数为7．626×1011nm2／min；等温锻烧温度低于1200℃时，晶粒生长活化能为64．35kJ／mol，晶粒生长表现为以表而扩散为主的聚合生长；等温锻烧温度高于1200℃时，晶粒生长活化能为116．40kJ／mol，晶粒生长表现为以晶格扩散为主的聚合生长；另外，还可见晶粒旋转驱动的聚合生长机制；低的晶粒生长激活能归因于大量氧空位的引入和晶粒旋转驱动的聚合生长机制。

The nanocrystalline ZrO2-8%Y203 （mass fraction） powder prepared by co-precipitation method was calcinated at high temperature from 1 100 ℃ to 1 300 ℃ for 2-32 h. The changes of the phase composition, morphology and particle size before and after the high temperature calcination were investigated by XRD, SEM and TEM, respectively. Both the grain growth kinetics and growth mechanism were analyzed. The results indicate that the contents of the monoclinic phase and tetragonal phase of ZrO2-8%Y203 powder decrease with increasing the temperature and time, the content of cubic phase increases with the increasing temperature and time. The grain size increases with increasing the temperature and time. At 1 250 ℃, the grain growth exponent is 6, and the kinetic rate constant is 7.626 x 1011 nm3/min. The grain growth is controlled by surface diffusion with lower activation energy （64.35 kJ） below 1 200 ℃, and controlled by lattice diffusion with higher activation energy （116.40 kJ） above 1 200℃. Grain-rotation-induced grain coalescence growth mechanism is also observed. Low growth activation energy is attributed to the introduction of large oxygen vacancies and grain-rotation-induced grain coalescence growth mechanism.