高温闪烁晶体Ce:YAlO_3开裂现象的分析

ANALYSIS OF THE CRACKING IN HIGH-TEMPERATURE SCINTILLATING CRYSTAL Ce∶YAlO_3

对提拉法生长的Ce∶YAlO3(简称为Ce∶YAP)晶体的开裂现象进行了研究,认为引起开裂的主要内在因素是YAP晶体热膨胀系数的各向异性。研究了Ce∶YAP晶体的[010],[101],[121]等几个主要方向在30～800℃范围内的热膨胀系数曲线。结果表明:沿[010]和[101]方向的膨胀系数相差最大。通过对晶体中热应力分布的计算,得出晶棱显露处为应力集中点,指出晶体容易产生开裂的方向是[010]和[101]。通过对晶体的显微形貌观察发现,晶体中存在微裂纹。晶体的各向异性热膨胀系数,晶体生长过程中大的温度梯度以及快的降温速率等是Ce∶YAP晶体产生开裂的主要原因。

According to the study on Ce:YAlO3 (Ce:YAP) crystals grown by the Czochralski method, the cracking is mainly attributed to its thermal expansion anisotropy. The thermal expansion coefficients of [010], [101] and [121] directions at temperatures of 30-800°C were investigated in detail. The results show that there is a larger difference of expansion coefficient between [010] and [101] directions. The calculation result shows that the stress concentrated points are at crystal edges, where the cracking tends to happen. The micro-cracking was observed mostly in the directions of [101] and [010]. The thermal expansion anisotropy in crystal, larger temperature gradient, faster temperature reducing rate in crystal growth, etc. are the main reasons of cracking in Ce:YAP crystals.