A Novel Convenient Synthesis of Mixed-Valence TiIII/TiIV Double Phosphates Starting with Titanium Nitride TiN

Abstract A new synthetic approach for the low- and mixed-valence double titanium phosphates starting with titanium nitride, TiN, and based on the controlled oxidation of a low-valent metal in the phosphate melt is presented. The reaction of the system M I 2 O - P 2 O 5 - TiN (M I = Na, K) in air (800-1050 °C) leads to loss of nitrogen, N 2 , and results in the formation of a number of double phosphates: KTiP 2 O 7 , K 2 TiniTiIV(PO 4 ) 3 , KTiOPO 4 , NaTiP 2 O 7 , NaTi 2 (PO 4 ) 3 and a new mixed-valent diphosphate, NaTi III Ti IV (P 2 O 7 ) 2 . The mixed-valent species K 2 Ti III Ti IV (PO 4 ) 3 and NaTi III Ti IV (P 2 O 7 ) 2 were characterized by single crystal X-ray diffraction. The described synthetic procedure is proposed as a simple and convenient method for the preparation of lowand mixed-valent phosphate materials