High-pressure and high-temperature multianvil synthesis of metastable polymorphs ofBi2O3: Crystal structure and electronic properties

Abstract

High-pressure and high-temperature experiments with Bi 2 O 3 using a 6-8 type multianvil device led to the formation of a metastable polymorph ͑HP-Bi 2 O 3 ͒ with noncentrosymmetric trigonal symmetry. This phase relaxes during the course of several months at ambient temperature or more rapidly via annealing, to a second intermediate modification ͑R-Bi 2 O 3 ͒. Upon further annealing finally the transformation back to the known ambient phase ͑␣-Bi 2 O 3 ͒ takes place. Both crystal structures were solved from high-resolution x-ray and neutron powder-diffraction data. The orientation and stereochemical activity of the Bi 3+ lone pairs ͑or inert pairs͒ is discussed in terms of crystal-chemical considerations and density-functional theory calculations. Whenever suitable, results were verified by experimental determination of the respective properties. The results of the theoretical analyses show that within the structure type of HP-Bi 2 O 3 , bismuth oxide exhibits a pronounced polarization and can be considered as ferroelectric.

Pleomorphic structural imperfections caused by pulsed Bi-implantation in the bulk and thin-film morphologies of TiO2

“…[16]. Despite of the fact that in both analyzed cases there are the signs of an α- [9]. So visually different FWHM of XPS O 1s spectra for the bulk and thin-film TiO 2 :Bi well agrees with our explanation because it is also the symptom of different from each other "metaloxygen" interactions in thin oxide films and bulk oxides but of the same element composition [27].…”

“…[31] display the sign for the third type of bismuth-oxygen bonding, but, as it was discussed in Refs. [9,30], the actually calculated third-type charge-value for surrounding oxygen is rather close to one from the mentioned above distinct and crystallographically independent oxygen types (the so-called pleomorphic bonding). This third-type oxygen charge-value might occurs due to asymmetry imperfections in coordination of structural polyhedrons or/and light geometric distortions in α-Bi 2 O 3 .…”

“…In order to combine suitable Bi 2 O 3 phases in terms of conductivity with the base compound of the newly fabricated photocatalyst (the final material is usually called Coupled Semiconductor -SC), the conventional technologies are applied, i.e. facile synthesis on the surface of oxide semiconducting host-matrix [4], ultrasonically dispersed deposition of previously synthesized Bi 2 O 3 [6], hi-pressure tempering technology [9], material chemistry methods [10]. [4].…”

β−Bi2O3under compression: Optical and elastic properties and electron density topology analysis

“…These calculations show that the β and β phases are thermodynamically not competitive with respect to many other phases (see Fig. 9), including: the monoclinic α-Bi 2 O 3 -type structure [76] above 0 GPa; the trigonal HP-Bi 2 O 3 -type structure [77] above 0.5 GPa; the hexagonal HPC-Bi 2 O 3 -type structure [78] above 1.5 GPa; the trigonal A-type rare-earth sesquioxide (A-RES) structure [79] above 7.9 GPa; the orthorhombic Rh 2 O 3 -II-type structure [80] below 4.1 GPa and above 11.1 GPa; and the orthorhombic ε-Bi 2 O 3 -type structure [81] above 21.8 GPa (see Fig. 9).…”

Amorphous phases and composition dependence of piezoelectricity in BaTiO 3 –Bi 2 O 3 polar amorphous ceramics

“…shows X-ray diffraction patterns of the sintered BaTiO 3 -xBi 2 O 3 composites.The starting Bi 2 O 3 was monoclinic α Bi 2 O 3[14].For the nonpiezoelectric x=0.15 composition, only the original BaTiO 3 and α Bi 2 O 3 could be detected in the sintered composites irrespective of the sintering temperature. However, α Bi 2 O 3 disappeared after the sintering process for the piezoelectric x=0.2-1 compositions.…”