Phase equilibria in the system La2O3-Na2O-P2O5

Abstract

In the ternary system La203-P2Os-Na20 the partial system La203-Na4LazP4015-LaPO4 has been examined by the thermal, dilatometrie X-ray and microscopic analyses and its phase diagram provided. The lanthanum oxyphosphate La3PO7 melts incongruently at the 1590~ temperature and crystallizes in a monoclinie system a = 11.20/~., b = 11.94/~, c=7.01 .~, ?= 93.79 and V = 936.97 A s.The purpose of present paper is to determine the phase diagram of the partial system La203-Na4La2P4015-LaPO4. As yet this system has not been known. It is limited from three sides by the following binary system: La203-LaPO4-; La203-Na4La2P4015; LaPO4-Na4La2P4015. The oxyphosphate with a formula La3PO7 for the first time has been obtained by Serra J. J. [1], in a solid state reaction from NH4H2PO4 and La203 at 1180 ~ and by chemical decomposition of the orthophosphate LaPO4 at a high temperature in an atmospheric pressure conditions [2]. Serra et al. [1] reported that the structures of La3PO7 and La7P3018 are monoclinic and LaTP3018 exists in lowand high -temperature forms, transforming reversibley at 1650 ~ Kizilyalli and Welch made La3PO7 by solid state reaction of LaPO4 with Na2CO3 at 700 ~ to 900 ~ [3]. Lanthanum oxyphosphate La3PO7 was found by quenching studies to have a slogish inversion at 935 ~ [4]. The oxyphosphate La3PO7 melts incongruently at 1590 ~ temperature [5,6].

Laser ablation of lanthanum phosphate for pulsed laser deposition

“…High‐temperature treatment of LaPO 4 under atmospheric pressure has been reported to result in decomposition with loss of gaseous oxides of phosphorus 29 . On resolidification of molten LaPO 4 (also known as Lanthanum Orthophosphate) formation of some oxyphosphate phases such as La 3 PO 7 and La 7 P 3 O 18 has been reported 26,30 . However, only on rapid quenching of the heated LaPO 4 target do such oxyphosphate phases survive, quenching rate required in the region of Δ T /Δ t >10 4 K sec −1 .…”