摘要
The electronic transition emission of Eu<sup>2+</sup> is in close relationship with the crystal-field environment and chemical bond property of Eu<sup>2+</sup> in hosts. The stronger the crystal-field intensity is, the larger the splitting of the 5d level is and the more favourable the broad band emission of d-f transition is. The smaller the covalency is, the smaller the
基金
Project supported by the National Natural Science Foundation of China.
