Synthesis of Sr-doped LaP3O9 single crystals and dense polycrystalline membranes in condensed phosphoric acid solutions

Growth of thin, c-axis oriented Sr-doped LaP3O9 electrolyte membranes in condensed phosphoric acid solutions

“…4 shows the typical X-ray diffraction patterns of the membranes. Single phase LaP 3 O 9 was obtained under all the conditions employed, which is in agreement with a previous report [16].…”

“…A key strategy has been the optimization of the grain size and crystal orientation, since the fast proton conduction pathways exist along the b-and caxes in the crystalline grains of LaP 3 O 9 [10]. The c-axis oriented polycrystalline membrane of Sr-doped LaP 3 O 9 with the thickness of ∼270 μm was successfully synthesized by precipitation in condensed phosphoric acid solutions, and it showed the higher conductivity (∼2 Â 10 À 4 S cm À 1 at 400°C) than those of randomly oriented sintered samples [10,16]. Its direct applicability to fuel cell electrolytes was also demonstrated.…”

Exploration of Dopant Species for Lanthanum Polyphosphate

“…The detailed procedure is available elsewhere. 19 First, starting materials were mixed at a proper ratio in perfluoroalkoxy (PFA) beakers or glassy carbon (GC) crucibles, and the mixtures were kept at 190…”

“…19 Upper surface is the plane facing to the solutions during the precipitation, and consists of large columnar grains (∼100 μm). Since the columnar grains are unidirectionally crystallized along c-axis, (001) planes tends to be oriented parallel to upper surface.…”

“…For example, higher doping levels can be achieved. 10,18 Additionally, larger and c-axisoriented grains can be obtained, 19 while grains are randomly oriented in the case of SSR. Larger grains reduce the density of grain boundary, which generally has an unignorable resistance against proton conducz E-mail: adachi.yoshinobu.36z@st.kyoto-u.ac.jp tion, and c-axis orientation enhances the bulk conductivity, because c-axis has one of the highest conductivities in LaP 3 O 9 crystal.…”