Synthesis and powder diffraction analysis of tri-rubidium penta-tantalum oxide, Rb₃Ta₅O₁₄, with novel three-dimensionally nanostructured Rb-bearing channels

<jats:p>The powder pattern of Rb<jats:sub>3</jats:sub>Ta<jats:sub>5</jats:sub>O<jats:sub>14</jats:sub> is reported here for the first time. Single crystals of Rb<jats:sub>3</jats:sub>Ta<jats:sub>5</jats:sub>O<jats:sub>14</jats:sub> of 0.1–0.2 mm in size were grown using a RbCl flux at 1100 °C. The Rb<jats:sub>3</jats:sub>Ta<jats:sub>5</jats:sub>O<jats:sub>14</jats:sub> powders were synthesized at 1200 °C by firing the Rb<jats:sub>2</jats:sub>CO<jats:sub>3</jats:sub> and Ta<jats:sub>2</jats:sub>O<jats:sub>5</jats:sub> raw materials with starting Rb/Ta ratios ranging from 0.450 to 0.800. The products with Rb/Ta ratios between 0.550 and 0.633 contained almost pure Rb<jats:sub>3</jats:sub>Ta<jats:sub>5</jats:sub>O<jats:sub>14</jats:sub> with Rb/Ta ratio of 0.600, while those with Rb/Ta ratio larger than 0.677 also contained the α form of Rb<jats:sub>4</jats:sub>Ta<jats:sub>6</jats:sub>O<jats:sub>17</jats:sub> with the Rb/Ta ratio of 0.677. Past studies of the synthesis and characterization of Rb<jats:sub>4</jats:sub>Ta<jats:sub>6</jats:sub>O<jats:sub>17</jats:sub> should be carefully examined in the light of possible coexistence with Rb<jats:sub>3</jats:sub>Ta<jats:sub>5</jats:sub>O<jats:sub>14</jats:sub>, because the former structure has not been completely solved, and thus the powder pattern is inaccurate, while the presence of the latter had not been known until the present study.</jats:p>