锗酸铅(Pb_5Ge_3O_(11))铁电单晶的生长与缺陷研究

Growth and Defects Study of Ferroelectric Lead Germanate Single Crystal

采用坩埚下降法成功生长了铁电锗酸铅 (Pb5Ge3 O11)单晶。所用Pt坩埚尺寸为2 5mm× 2 0 0mm和10mm×6 0mm ,炉温控制在高于熔点 5 0～ 80℃ ,固液界面温度梯度小于 2 5℃ /cm ,生长速率小于 0 .5mm/h。所得晶体呈浅棕色 ,最大尺寸达2 5mm× 6 0mm。采用光学显微镜 (OM)及电子探针 (EPMA)研究了所得晶体的生长缺陷 (气泡、包裹体等 ) ,讨论了产生这些缺陷的原因 ,提出了控制及减少此类缺陷的方法。

Ferroelectric lead germanate (Pb_5Ge_3O_(11)) single crystals were grown successfully by the modified Bridgman method. Pt crucible of 25mm×200mm with a seed well of 10mm×60mm was used, the furnace temperature was 50-80℃ higher than melting point, temperature gradient in crystal-melt interface was less than 25℃/cm and growth rate was less than 0.5mm/h. Brownish Pb_5Ge_3O_(11) crystal up to 25mm in diameter and 60mm in length was obtained. Growth defects, such as bubles, inclusions, were investigated by means of OM and EPMA. The methods to eliminate above macrodefects were suggested.