The investigation of alkali metal salts of zirconium and hafnium phosphates began in connection with the study of similar thorium and tetravalent uraniumphosphates. The common formula of these compounds is M1M ~v (P04) 3 withM 1 = Li, Na, K, Rb, Cs and M 1Y = Th, U, Zr, Hf. The crystal growth and crystallographicdata of NaTh2(P04) 3 , NaU2 (P04 ) 3 and KTh2 (P04 ) 3 have alreadybeen published1 ,2 • They are monoclinic, space groups C2 /c or Cc with four formula
weights per unit cell, and have very close lattice parameters. The questionis whether a similar compound with tetravalent metal other than thorium oruranium(IV) can be prepared in a similar way and whether it has similar crystallographic
properties
