Rietveld refinements and vibrational spectroscopic studies of Na1−xKxPb4(PO4)3 lacunar apatites (0≤x≤1)

► Synthesis and characterization of new double perovskites and apatites. ► XRD and Raman spectroscopy studies of double perovskites and MAX phases. ► Pressure, temperature and compositions induced phase transitions in these materials. ► Structural determination/refinement of these compounds as a function T, P and x.