研究了高温富锂气氛下锂离子在低掺镁铌酸锂晶体中的扩散.采用气相输运平衡法制备了掺杂1mol% MgO的不同锂含量的铌酸锂(Mg1LN)晶体,采用热分析仪测试了晶体的居里温度.制备了一系列不同锂含量的Mg1LN多晶料,拟合了晶体锂含量与居里温度的关系.采用Boltzmann-Matano法求解了扩散方程.结果表明,扩散温度为1100 ℃时,Mg1LN晶体中锂离子扩散系数为3.2×10-9~13.0×10-9 cm2/s,当扩散温度为1145 ℃时锂离子扩散系数约是1100 ℃时扩散系数的三倍.因此,适当提高扩散温度是提高气相输运平衡法制备近化学计量比低掺镁铌酸锂晶体效率的有效办法.
Lithium diffusion in low MgO-doped LiNbO3 crystals was investigated under Li rich environment at high temperature.The vapor transport equilibration (VTE) method was used to prepare 1 mol% MgO-doped LiNbO3 (Mg1LN) crystals with widely varying diffusion-limited Li2O content profiles.The thermal analyzer was used to measure the Curie temperature of samples.Mg1LN polycrystalline powders with different Li2O content were prepared to fit the correlation between the Li2O content and Curie temperature.A Boltzmann-Matano mathematical method was used to solve the diffusion equation.Results show that at the temperature of 1100 ℃, the diffusivity of Li+ increases from 3.2×10-9 cm2/s ([Li2O] is 48.7mol%) to 13.0×10-9 cm2/s ([Li2O] is 49.56mol%), and the diffusivity increases nearly three times at 1145 ℃ than that at 1100 ℃.It can be concluded that increasing the diffusion temperature reasonably is an effective way to improve the efficiency for preparing stoichiometric low MgO-doped LiNbO3 crystals by VTE method.
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