Sintering of lanthanum zirconate

Lanthanum zirconate (La₂Zr₂O₇) was prepared by coprecipitating lanthanum nitrate and zirconyl oxychloride at pH 10, followed by ethanol washing. The initial high surface area of approx. 304 m²·g^-1 decreased very rapidly with increased sintering temperature and decreased to an immeasurably small value after heating at 1200°C for 15 h. The major parameters studied were phase evolution, crystallite size, porosity, surface area reduction, and shrinkage during sintering. Three temperature regions were identified based on these studies: below the crystallization temperature, between the crystallization temperature and approx. 1100°C, and above 1100°C. The main contribution of surface area reduction in the region 800°-1100°C was due to surface diffusion; the main contribution above 1100°C was due to grain-boundary diffusion coupled with surface diffusion.