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研究了掺镁掺铁铌酸锂晶体的紫外、可见及红外光谱 ,首次发现当掺镁量超过通常所说的阈值 (第一阀值 )时 ,Fe3+ 离子和部分Fe2 + 离子的晶格占位由锂位变为铌位 ,但仍有部分Fe2 + 离子留在锂位 .晶体缺陷化学分析表明 ,继续增加掺镁量 ,占锂位的Fe2 + 离子数将逐渐减少 ;当掺镁量达到另一个适当的值 (第二阀值 )时 ,全部Fe2 + 都占铌位 ,晶体的抗光折变能力空前提高 ,这种现象称作双阈值效应 .
The UV, visible and infrared spectra of Mg-doped Fe-doped lithium niobate crystals have been investigated. It was first found that the lattice occupancy of Fe3 + ions and some Fe2 + ions when the Mg content exceeds the so-called threshold (first threshold) However, some Fe2 + ions still remain in the lithium sites. The chemical analysis of the crystal defects shows that the number of Fe2 + ions in the lithium sites will continue to decrease while the amount of Mg2 + At an appropriate value (second threshold), all Fe2 + occupy the niobium position and the photorefractive properties of the crystal have been previously unparalleled, a phenomenon known as double threshold effect.