A structural study of the hexagonal potassium tungsten bronze, K0.26WO3

Vibrational properties of ferroelectric hexagonal tungsten bronzes ABxW3−xO9, where A = K, Rb, Cs and B = Nb, Ta, Zr, Cr

“…Since, however, the distortion from the hexagonal structure is small, we can use in the vibrational analysis the results of the x-ray investigation performed by Yanovskii et al 1 According to this study, the high-temperature phase is most likely described by the space group P6 3 22 and the primitive cell contains two AB x W 3 x O 9 units (26 atoms). 1 The same crystal structure was found 15,16 for K 0.26 WO 3 and Cs 0.29 WO 3 . The results of the factor group analysis are presented in Table 2.…”

Vibrational spectra of KNbW2O9 hexagonal tungsten bronze

“…P6 3 22. 3,9 Although the ambient temperature crystal structure of KNbW 2 O 9 is lower than hexagonal, the distortion of the lattice is not evidenced by the x-ray data. 3 Therefore, it is reasonable to assume that the vibrational properties at ambient temperature are similar to those at high temperature, and that to a first approximation we may use the results of factor group analysis performed for the P6 3 22 structure.…”

“…Although the detailed crystal structure is not known, we have noticed that the same space group was found for K 0.26 WO 3 . 9 We may suppose, therefore, that the prototype structures of K 0.26 WO 3 and KNbW 2 O 9 are the same. This allows us to calculate the number of expected vibrational modes for KNbW 2 O 9 and to compare the experimental results with the predictions.…”

Structure and properties of the KNbW2O9 hexagonal bronze doped with Eu3+ ions as an optically active probe

“…It is known, however, that in the case of K 0.26 WO 3 these oxygen atoms are not coplanar, i.e. the octahedra are tilted and as a result the hexagonal rings are puckered [9]. The structure is described then by the P6 3 22 space group.…”

“…This compound was studied by means of dielectric, electron microscopy, X-ray diffraction methods as well as IR and Raman spectroscopic methods [2][3][4][5][6][7][8]. These studies suggested that the high-temperature phase could be described in the P6 3 22 space group, which was also found for K 0.26 WO 3 [9]. Our previous work showed that the structure of KNbW 2 O 9 is lower than hexagonal with a small distortion of the lattice [8].…”