The influence of second coordination-sphere interactions on the luminescent properties of β-Ca3(PO4)2-related compounds

Ca8CdEu(PO4)7 polycrystalline material with a β-Ca3(PO4)2-type (β-TCP) structure was obtained using a solid state technique. The structure was refined by Rietveld method using powder synchrotron X-ray diffraction data. The analysis of applying approaches confirmed that the Ca8CdEu(PO4)7 structure is similar to R3¯с structures of Ca8MEu(PO4)7 (M = Mg, Zn). The photoluminescence properties were studied under UV excitation and compared with previously investigated Ca8MEu(PO4)7 (M = Mg, Zn, Ca). The substitution of Ca2+ by M2+ influences on the efficiency of energy transfer between the host and the luminescent ion. The influence of second coordination-sphere interactions on the luminescent properties of Ca8MEu(PO4)7 was revealed. Based on the difference on the PL spectra of Eu3+ in Ca8MEu(PO4)7 with R3с or R3¯с structures the site-selective method for determination of space group in β-TCP-type compounds was proposed. It is thus shown that the Eu3+ was used as an optical probe to determine the site symmetry of studied hosts. [Display omitted] •Ca8CdEu(PO4)7 red phosphor with a β-TCP structure was synthesized by a solid state technique.•The structure and luminescent properties were systematically studied.•The site-selective method for determination of space group in β-TCP-type compounds was proposed.•The properties of Ca8CdEu(PO4)7 were compare with Ca8MEu(PO4)7 similar compounds.