Abstract
Photoluminescence excitation and emission spectra of new phosphate Ca8ZnEu(PO4)7 have been investigated. The influence of the composition on the luminescence intensity has been shown. The substitution of Zn2+ for Ca2+ in Ca9Eu(PO4)7 with the formation of Ca8ZnEu(PO4)7 leads to the increased emission intensity 5D0 → 7F2 by about 1.5 times and to decreased number of bands from three to one in the range of 5D0 → 7F0 transition. Conditions of preparation do not influence the luminescent properties and distribution of Eu3+ cations in the structure. DSC, SHG data and dielectric spectroscopy reveal that Ca8ZnEu(PO4)7 belongs to antiferroelectrics (Tc = 836 K). The first-order antiferroelectric/paraelectric transformations are accompanied by a changing symmetry (R3¯с to R3¯m). The structure of Ca8ZnEu(PO4)7 (sp. gr. R3¯с) was refined by the Rietveld method. The Zn2+ cations occupy the M5 site. The Eu3+ and Ca2+ ions are located in the M1 and M3 sites of β-Ca3(PO4)2-type structure.
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