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首页> 外文期刊>Journal of Alloys and Compounds: An Interdisciplinary Journal of Materials Science and Solid-state Chemistry and Physics >Sintering of BaZrO_3 and SrZrO_3 perovskites: Role of substitutions by yttrium or ytterbium
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Sintering of BaZrO_3 and SrZrO_3 perovskites: Role of substitutions by yttrium or ytterbium

机译：BaZrO_3和SrZrO_3钙钛矿的烧结：钇或的替代作用

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The modification of perovskite sintering oxides A~(II)B~(IV)O_3 was studied. The alkaline earth metal plays a role in the densification of perovskite. The effect of the substitution of Zr~(4+) by a lanthanide Yb~(3+) in barium zirconate (BZYb) increases its density and impedes BaO evaporation independently of the thermal cycle. A substitution of Zr~(4+) by Y~(3+) increases the density of barium zirconate (BZ) only after 4 h at 1650 °C. In all cases, the substitutions of Zr~(4+) by Y~(3+)or Yb~(2+ or 3+) in the zirconate inhibit grain growth. The substitution in B site by a Ln~(3+) leads to the creation of vacancies (A~(II)B~(IV)_(1-x))Ln~(III)_xO_((3-x)/2)). To determine the vacancies' role, three different controlled atmospheres were tested. Argon, dry air, and oxygen were used to study the impact on the linear shrinkage of barium zirconate when some Zr~(4+) are replaced by yttrium or ytterbium (BZY, BZYb) or not substituted (BZ). Strontium zirconate (SZ) is not as chemically stable as barium zirconate (BZ) during the thermal cycle when Yb is used as a substitution element. In effect, the presence of the secondary phase Zr_3Yb_4O_(12) associated with the release of oxygen proves the bivalence of ytterbium (Yb~(2+) or Yb~(3+)). Therefore, ytterbium can be substituted in either A or/and B sites. The study of reactive sintering between lanthanum strontium zirconate (SZYb) and Yb_2O_3 shows that a slight excess of Yb_2O_3 around SZYb grains stabilizes the chemical composition of SZYb. Perovskite symmetry and stability were determined by two factors, i.e., tolerance (t) and octahedral factors (r_B/r_O). It was demonstrated that the distortion of the perovskite unit cell increases the density of pellets.
机译：研究了钙钛矿烧结氧化物A〜（II）B〜（IV）O_3的改性。碱土金属在钙钛矿的致密化中起作用。锆酸钡（BZYb）中的镧系元素Yb〜（3+）取代Zr〜（4+）的效果增加了其密度，并阻碍了BaO的蒸发，而与热循环无关。仅在1650°C 4小时后，用Y〜（3+）替代Zr〜（4+）才能增加锆酸钡（BZ）的密度。在所有情况下，锆酸盐中的Y〜（3+）或Yb〜（2+或3+）替代Zr〜（4+）都会抑制晶粒长大。 Ln〜（3+）取代B位导致空位（A〜（II）B〜（IV）_（1-x））Ln〜（III）_xO _（（3-x）/ 2））。为了确定职位空缺的作用，测试了三种不同的受控气氛。用氩气，干燥空气和氧气研究了当某些Zr〜（4+）被钇或（BZY，BZYb）或未取代（BZ）取代时，锆酸钡对线性收缩的影响。当将Yb用作替代元素时，在热循环过程中，锆酸锶（SZ）的化学稳定性不如锆酸钡（BZ）稳定。实际上，与氧气释放相关的第二相Zr_3Yb_4O_（12）的存在证明了the的两价（Yb〜（2+）或Yb〜（3+））。因此，can可以在A或B位被取代。锆酸镧锶（SZYb）和Yb_2O_3之间的反应性烧结研究表明，在SZYb晶粒周围略有过量的Yb_2O_3稳定了SZYb的化学成分。钙钛矿的对称性和稳定性取决于两个因素，即公差（t）和八面体因素（r_B / r_O）。已经证明钙钛矿晶胞的变形增加了颗粒的密度。

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