Ｃａ１－ｘＢａｘＺｒ４（ＰＯ４）６（０≤ｘ ≤１，简称ＣＢＺＰ）是由具有相反热膨胀异向性的 ＣａＺｒ４（ＰＯ４）６和ＢａＺｒ４（ＰＯ４）６互溶形成的二元固溶体型ＮＺＰ族陶瓷，其热膨胀系数具有可裁剪性．本研究的主要目的是通过调整组成，制备具有较好耐热冲击性的零膨胀材料．为此，首次用共沉淀法合成了单相的 ＣＢＺＰ系列粉体。分别添加 ３％ＺｎＯ和 ４％ＭｇＯ为烧结助剂，制成Ｔ ＣＢＺＰ系列陶瓷材料，用热机械分析（ＴＭＡ）压缩法测定了试样在２０～１０００℃的平均线膨胀系数ａ２０／１０００，以及加热（２０～１０００℃）和冷却（１０００～４００℃）过程的热膨胀曲线．实验结果表明，添加 ＺｎＯ和 ＭｇＯ时的近零膨胀材料分别为Ｃａ０．８５Ｂａ０．１５Ｚｒ４（ＰＯ４）６（ｘ＝０．１５）和ＣａＺｒ４（ＰＯ４）６（ｘ＝０），α２０／１０００依次为 ０．６×１０－６／°Ｃ和一０．８×１０－６／°Ｃ，但热膨胀曲线上却由于微裂纹的产生而呈现出较大的滞后环，耐热冲击性不理想．可见，对ＣＢＺＰ系列而言，调整组成虽然能实现零膨胀，但很难消除热膨胀异向性，提高其耐热冲击性的有效途径可能是适当抑制晶粒生长以避免产生过多的微裂纹．
Ca1-xBaxZr4(PO4)6(0≤ x≤1, abbrev CBZP) which belongs to NZP family is a new
crystalline soild-solution, it may be possible to utilize the opposite anisotropic behavior of thermal expansion in CaZr4(PO4)6 and
BaZr4(PO4)6 to make the magnitude of thermal expansion coefficient be tailored. The main objective of this study was to prepare the material
with near-zero thermal expansion and lower anisotropy by adjusting composition, and the single phase CBZP was synthesized by
copreciptate methods. The compacts were sintered at temperatures of 1100℃ or 1300℃ with the addition of 3%ZnO or 4%MgO for 2h. Their average thermal expansion coefficients from
20～1000℃ and their thermal expansion curves during heating (from 20～1000℃)and cooling(from 1000～--400℃) were measured by TMA compressing method. The results show that some
compositions with near-zero thermal expansion are Ca0.85Ba0.15Zr4(PO4)6 when addition of 3%ZnO and CaZr4(PO4)6 when addition of 4%MgO,
the linear expansion coefficients is 0.6×10-6/℃ and --0.8×10-6/℃ respectively. But their thermal expansion curves show hysteresis loops due to microcracking, and the property of thermal
shock resistance is not perfect. It can be concluded that it is difficult to minimize their anisotropy by adjusting composition, though the near-zero
compositions can be abstained by this means. The useful route of improving their property of thermal shock resistance is properly to suppress the grain
growth beyond the transition grain size with an additive (example for SiO2) during the sintering period to decrease microcracking.
参考文献
| [1] | Ota T, Yamai I. J. Am. Ceram. Soc., 1986, 69 (1): 1--6. [2] Limaye S Y, et al. J. Am. Ceram. Soc., 1987, 10: C232--C236. [3] Limaye S Y, et al. J. Mater. Sci., 1991, 26: 93--98. [4] 李全喜, 等. 云南化工, 1998, 3: 20--22. [5] 刘雄. 热分析技术基础. 昆明: 昆明贵金属研究所自编讲义, 1985. [6] 胡晓珍, 等. 材料科学与工程, 1998, 2: 39--42. [7] Yamai I, Ota T. J. Am. Ceram. Soc., 1993, 2: 487--491. |
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