Crystal growth and structure determinations of potassium hafnates: K2Hf2O5 and K4Hf5O12

Crystals of K2Hf2O5 and K4Hf5O12 were grown from molten potassium hydroxide flux. The crystal structures were determined by single-crystal X-ray diffraction. K2Hf2O5 crystallizes in the space group Pnna of the orthorhombic system, with unit cell dimensions of a = 5.780(1) إ, b = 10.640(2) إ, and c = 8.666(2) إ. This compound contains infinite chains of HfO6 octahedra that form a channel structure. K4Hf5O12 crystallizes in the space group P 3 ¯ m 1 of the trigonal system, with unit cell dimensions of a = 5.7877(2) إ and c = 10.3693(7) إ. This compound possesses a layered structure with six-coordinate Hf in three different coordination environments (trigonal prismatic, distorted octahedral, and regular octahedral).