Microwave‐assisted Hydrothermal Synthesis of Single‐crystal Nanorods of Rhabdophane‐type Sr ‐doped LaPO 4 · n H 2 O

A novel, simple, soft, and fast microwave‐assisted hydrothermal method was used for the preparation of single‐crystal nanorods of hexagonal rhabdophane‐type La 1− x Sr x PO 4− x /2 · n H 2 O ( x = 0 or 0.02) from commercially available La ( NO 3 ) 3 ·6 H 2 O , Sr ( NO 3 ) 2 , and H 3 PO 4 . The synthesis was conducted at 130°C for 20 min in a sealed‐vessel microwave reactor specifically designed for synthetic applications, and the resulting products were characterized using a wide battery of analytical techniques. Highly uniform, well‐shaped nanorods of LaPO 4 · n H 2 O and La 0.98 Sr 0.02 PO 3.99 · n H 2 O were readily obtained, with average length of 213 ± 41 nm and 102 ± 25 nm, average aspect ratio (ratio between length and diameter) of 21 ± 9 and 12 ± 5, and specific surface area of 45 ± 2 and 51 ± 1 m 2 /g, respectively. In both cases, the single‐crystal nanorods grew anisotropically along their c crystallographic‐axis direction. At 700°C, the hexagonal rhabdophane‐type phase has already transformed into the monoclinic monazite‐type structure, although the undoped and Sr ‐doped nanorods retain their morphological features and specific surface area during calcination.