Rb3Y2(PO4)3 and Rb3La(PO4)2, undoped and doped with Eu3+ ions, were synthesised either by the Pechini method or solid state reaction. They were characterised by thermoanalytical methods, X-ray diffraction, IR and Raman spectroscopy as well as optical techniques. It was stated that Pechini and solid state reaction methods give the compounds with the same structure. The structural data result in the P21/m space group with Z = 2 and a = 9.78 Å, b = 5.76 Å and c = 7.77 Å cell parameters for Rb3La(PO4)2 and cubic symmetry I21/3 with a = 16.87 Å and Z = 16 for Rb3Yb2(PO4)3. In Rb3La(PO4)2 the reversible β/α phase transition is observed in the 960–1070 °C temperature range. The lifetime of the 5D0 excited state measured at 77 K is about 4 and 2 ms for Rb3La(PO4)2 and Rb3Y2(PO4)3, respectively.
