Segregation of Sr in Sr-doped LaPO4 ceramics

Synthesis and characterization of monazite-type Sr:LaPO4 prepared through coprecipitation

“…NH 4 NO 3 is obtained as a byproduct of the coprecipitation reaction. According to the nitrogen analysis, the nitrate is totally eliminated after calcination at 800 • C. The XRD data indicate that the peaks position do not change with the subtitution of La 3+ by Sr 2+ into the monazite-type LaPO 4 lattice. In addition, as the size of the two ions is quite similar, it is possible that the Sr 2+ ions occupy the La 3+ position in the monazite-type LaPO 4 crystal.…”

“…However, one of the main problems which has been revealed in a former study is the possible presence of a second phase, probably Sr 3 La(PO 4 ) 3 , for doping percentages higher than 5 mol% after sintering. 4 It is well known that impurities are an obstacle for the proton mobility and are the cause of a loss of conductivity. At the same time, it is important that the preparation is fast and cheap and gives dense and gas-tight materials (>93% of the theoretical density).…”

Extended solubility of Sr in LaPO4 monazite

“…[10] Therefore, divalent (Ca 2+ , Sr 2+ )-doped LaPO4 has been investigated as a prospective protonic conductive material. [11][12][13] Interestingly, the published research reports widely varying Sr substitutional concentrations [11,[14][15][16][17] which may be due to different (OH) -content.…”

“…[ 17 ] The direct precipitation method used here [ 20 ] , directly precipitates Sr-doped monoclinic LaPO4 monazite without any heat treatment required. Theoretically via the direct precipitation method, Sr-doped LaPO4 containing a high concentration of Sr can be synthesized.…”

“…[ 17 ] and Hatada et al [15] Hatada et al reported that after heating Sr-doped LaPO4 at 800°C in N2 environment, H2O evaporated and the unit cell volume decreased and Sr2P2O7 formed after sintering at 1200°C for 5 hours. Since the P-O-H vibration peak in FTIR disappears (Fig.…”