Ceramic phosphates of formula NaZr2(PO4)3 (NZP) containing alkali, alk
aline earth, Nd, Zr, and Nb are prepared. According to x-ray phase ana
lysis, IR spectroscopy, and electron microprobe analysis, the formula
and structure of the phosphates are unchanged after contact with H2O a
t 200-400-degrees-C and 600 atm and with chloride solutions and seawat
er. Leach rates are (3-7).10(16) for Cs and 3.10(-5) g/cm2.day for Na
in H2O at 200-400-degrees-C.