Condensed Phonon Modes in Successive Phases of WO₃

Polaron and phonon properties in proton intercalated amorphous tungsten oxide thin films

“…[9][10][11] In a simplified description, the crystal structure of WO 3 is regarded as a modification of the perovskite-type ABO 3 lattice, in which the A site remains unoccupied and the W atoms occupy the B site. This produces a three-dimensional network of corner-shared octahedra WO 6 .…”

“…This produces a three-dimensional network of corner-shared octahedra WO 6 . 9,[12][13][14][15] The tungsten oxide crystal structure is very unstable because the decrease in ion size of the A site in the ABX 3 perovskite structure increases the instability of the structure, which is most unstable in WO 3 because the ion for the A site is missing. Preparation of amorphous tungsten oxide thin films is feasible with magnetron sputtering at room temperature and at convenient plasma conditions.…”

Color centres and polymorphism in pure WO3 and mixed (1−x)WO3−y·xReO2 powders

“…The crystal structure of WO 3 can be described as derivafives of an ideal cubic structure based on corner-sharing [WO6] octahedra, known as the ReO3-type structure [12]. The different degrees of distortion with respect to the ideal cubic structure are caused by the second order Jahn-Teller effect [12,15], reflecting an interplay between the lattice phonons and the electronic bands.…”

Polarity sensitive electro-optical response in liquid crystal devices due to ionic diffusion in WO3 thin films

“…In principle, the reversible intercalation-deintercalation processes of small ions occur in WO3 bulk crystals. It shows a very complex polymorphism [10][11][12][13][14], strongly dependent also *) Author for correspondence: E-mail: Strangi@fis.unical.it on electronic impurities, grain size distribution, thermal and mechanical history [15], but all the various phases can be considered as successive deformations, associated to phonon condensation [16], of a simple cubic structure of ReO 3 type, based on corner-sharing octahedral units WO6; the guest cations can enter in available interstitial sites between such octahedra.…”

“…Dehydration reactions and structural transformations of the films, strongly affecting the ionic conductivity, can be obtained by thermal annealing [32,33]. In general, high temperature annealing of the WO 3 samples lead to a crystalline structure belonging to the standard sequence [16] derived from cubic ReO3 structure. The temperature value necessary to this transition depends in some amount on the bulk or thin film character of the sample and on the deposition technique; its variations are reported between 300 ~ for evaporated films [32] and 500 ~ for films prepared by the sol-gel process [22].…”