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在以往的研究工作中，人们经常关注给定基质具有多个格位所对应多发光中心的光致发射。取决于所掺杂的基质，多个格位的晶体化合物应该可以提供相应的多发光中心，但某些化合物有时只会表现一个发光中心，由此产生“争议性”发光中心。据以往研究，以稀土离子掺杂而为人所知的经典镁黄长石（ Ca2 MgSi2 O7）长余辉化合物具有“争议性”Ca格位。为此，在本文中以非稀土离子（ Bi3＋）特有的发光特性从侧面来研究Ca2 MgSi2 O7化合物中的“争议性”Ca格位问题。结果表明，在250和276 nm激发波长激发下，所有的Bi3＋掺杂Ca2 MgSi2 O7样品均有峰位位于582和350 nm的两个Bi3＋特征发射带。结合晶体结构分析，光谱结果表明，Ca2 MgSi2 O7∶Bi3＋荧光粉具有对应于六配位和八配位的两个不同Ca2＋格位的两个Bi3＋发光中心，即，Bi3＋（Ⅰ）（～582 nm）和Bi3＋（Ⅱ）（～350 nm）发光中心。此外，光谱分析进一步表明，Bi3＋（Ⅰ）与Bi3＋（Ⅱ）具有单向的能量传递，而且，发现这两个发光中心所对应的相对发射强度是依赖于激发波长和Bi3＋掺杂浓度。实验证明了Ca2 MgSi2 O7晶体化合物具有两个Ca格位，而不是有些工作中所讨论的一个Ca格位。本文工作可以为已知或未知的具有“争议性”格位的晶体化合物的验证提供新的借鉴。

Multi-photoemissions from multi-luminescent centers that correspond to multi available sites in a given crystal are frequently noticed in previous works .Depending on the exact type of dopant built into , compounds having multi available sites should correspondingly offer multi luminescent centers , but some kinds of such compounds sometimes exhibit only one luminescent center , exhibiting the “controversial” centers.According to previous works , the akermanite(Ca2MgSi2O7), which has been known as the classical afterglow host for a long term , belongs to this type of compounds having the “controversial” Ca sites.Here we report on utilizing the typical luminescent behavior of the non-rare-earth(non-RE) ion(Bi3+) to explore the issues of “controversial” Ca sites in Ca2MgSi2O7 crystal.Our results show that the excitation bands centering at 250 nm and 276 nm can pump all samples of Ca2 MgSi2 O7∶Bi3+to exhibit dual Bi3+-related photoemissions centering at 582 nm and ~350 nm, respectively.In combination with the crystal structure analysis , the spectral results indicate that there are dual Bi 3+luminescent centers [ denoted as Bi 3+(Ⅰ) and Bi3+(Ⅱ)] at two different Ca2+sites coordinating with six-and eight-oxygen atoms in the Ca2MgSi2O7 host.Surprisingly, the spectral results support the existence of the energy transfer from Bi 3+(Ⅰ) to Bi3+(Ⅱ) and the process is found to be unidirectional .Further analysis indicated that the relative emission intensity of 582 nm and~350 nm derived from Bi 3+(Ⅰ) and Bi3+(Ⅱ) centers is tightly relied on the incident excitation wavelength and the Bi3+doping contents .Our results clearly prove that there are two available Ca sites instead of only one Ca site in Ca2 MgSi2 O7 crystal.Because of the reason , this work provides a new insight into verifying the available sites in some unknown or/and well-known crystals from another point of view .