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Single-crystalline species of the novel compounds BaBiBO4 and CaBi2B2O7 with Pna21 structure were successfully grown by the top-seed solution growth (TSSG) method and solid-state recrystallization, respectively. X-ray diffraction methods were used to confirm the symmetry of the crystal structure and to determine unit cell parameters. Normal-mode classification and assignment were performed from the results of polarized Raman and IR absorption measurements on the obtained crystals. The high-frequency part of the vibrational spectra of both materials (580–1400 cm−1) is reminiscent of the normal modes of the isolated [BO3]3− group. The expected crystal-field induced changes in these modes from group-theoretical considerations provide important clues for the normal-mode assignment of the high-frequency spectral lines.

Bi12 SiO20 crystals doped with Os, Re, Ru, and Rh were grown by the Czochralski technique, and their conductivity (real and imaginary parts) was measured as a function of temperature and frequency. The results are interpreted as evidence that the charge transport in the crystals is due to hopping along chains of localized states.

The main processes for preparing bulk single crystals and films of photorefractive and piezoelectric Bi 12 M x O 20 ± δ (M = Group II-VIII elements) sillenite compounds are considered. Experimental data are sum- marized on the crystal growth of Bi 12 M x O 20 ± δ from the melt and under hydrothermal conditions, and the key morphological features of sillenites are analyzed. Various types of macroscopic growth defects in sillenite-type crystals are described, and their origin is discussed. The compositions of second-phase inclusions in undoped and doped (Group I-VIII elements) Bi 12 SiO 20 , Bi 12 GeO 20 , and Bi 12 TiO 20 single crystals are presented, and the main physicochemical properties of various Bi 12 M x O 20 ± δ crystals are summarized.

The photoinduced absorption in a Ca-doped bismuth titanate crystal is measured as a function of temperature in the red (660 nm), yellow (570 nm), and green (505 nm) spectral regions.

Evidence that local ordered magnetic fields from 30 to 250 G exist in bismuth-based diamagnetic compounds comprising neither d- nor f-elements was given by 209Bi NQR spectroscopy and supported by SQUID measurements of α-Bi2O3. The NQR experiments involved a study of the zero-field line shapes, analysis of the Zeeman-perturbed patterns, and examination of the zero-field spin-echo envelopes in single crystals and powders. The results of the experiments followed by computer modeling of the observed spectra were interpreted assuming that ordered magnetic fields are located at the bismuth sites in α-Bi2O3, Bi3O4Br, Bi2Al4O9, Bi4Ge3O12, Bi2Ge3O9 and perhaps in Bi3B5O12. A survey of the related 209Bi NQR data is here presented.

Results of investigations into the dynamics of light-induced absorption in bismuth titanium oxide crystals doped with calcium (Bi12TiO20:Ca) illuminated with quasimonochromatic light of semiconductor light-emitting diodes at two wavelengths from the set λ = 870, 660, and 525 nm are presented. Based on an analysis of the experimental data, a model of charge transfer by defect centers describing the observed phenomena is suggested.

The results of experimental investigations into the dynamics of light-induced absorption for coherent incident light (the wavelength λ = 633 nm) and incoherent radiation of a light emitting diode (λ ≈ 660 nm) in single bismuth titanate crystals with different stoichiometric structures are presented. It is demonstrated that the dynamics of two-wave interaction on the photorefractive reflection grating in (100)-cut samples illuminated with coherent light is nonmonotonic in character. Light-induced changes in the absorption coefficient and the efficiency of interaction on the reflection grating increase when the titanium oxide content in the examined samples decreases.

The results of investigations into the dynamics of the light-induced absorption and of its dark relaxation in a Bi12TiO20 : Ca single crystal are presented. To illuminate the crystal and to measure the induced changes in the absorption, narrow-band radiation of an incoherent semiconductor light-emitting diode with the wavelength λ = 660 nm close to that of a helium-neon laser was used. The material parameters of the crystal are estimated based on a comparison of the experimental data with the results of calculations for a theoretical model that takes into consideration doubly ionized donor centers and shallow traps.

The absorption and circular dichroism spectra of Nd-doped Bi12SiO20 crystals were measured in the range 10 000 to 20 000 cm–1. The spectra showed electronic transitions related to only one type of Nd-related center: Nd substituting for Bi in position with symmetry C1. The bands due to the transitions from the first Stark component of the ground state to Stark components of excites states (4I9/2 → 4G5/2 , 4I9/2 → 2G7/2 , and 4I9/2 → 4G7/2) were analyzed in detail. The dipole strength D0k , rotatory power R0k , and anisotropy factor G0k of these transitions were calculated. The intensities of transitions to Stark components were shown to vary by more than one order of magnitude within an excited-state multiplet. The anisotropy factors of the 4I9/2 → 2G7/2 and 4I9/2 → 4G7/2 transitions, allowed in the magnetic dipole approximation, are, on the average, larger than that of the 4I9/2 → 4G5/2 transition, which points to a significant contribution of the magnetic moment (λ λ2) to the total intensity of the transition.

It was earlier found from nuclear quadrupole resonance (NQR) measurements and computer modeling that α-Bi2O3, Bi3O4Br and mixed oxides Bi2O3· 2Al2O3, Bi2O3· 2Ga2O3, Bi2O3· 3GeO2, and 2Bi2O3· 3GeO2exhibit local ordered magnetic fields from 30 to 200 G. It thus follows that these compounds are not diamagnets in a conventional sence of the word. With the aim of revealing previously unknown magnetic properties in bismuth(III) oxide-based Main Group element compounds, the mixed bismuth–boron oxides 2Bi2O3· B2O3, 3Bi2O3· 5B2O3, and Bi2O3· 3B2O3were prepared and studied using 209Bi NQR. The quadrupole interactions of the 209Bi nuclei and their electronic environment were studied, the crystallochemical features of the compounds were discussed, and the conformity of the 209Bi results to the X-ray structure data was verified. The preliminary tests in the field of a permanent magnet showed that the resonance intensities increase in external magnetic fields, indicating that a magnetism of unknown nature develops in the titled compounds. It was found reasonable to continue studies of the magnetic properties of these compounds using single-crystal 209Bi NQR in external magnetic fields.

The experimental data of the past 10–15 years for the vibrational spectra of crystals with the structure of sillenite Bi12M x O20±δ obtained by the methods of laser Raman scattering and infrared (IR) absorption are generalized. Correlations between the chemical composition and crystal structure of the compounds (variations of the cation M) and their vibrational spectra are established. It is shown that the main contribution to formation of the high‐frequency part of the spectrum of two‐, three‐, and four‐phonon absorption is given by phonons related to vibrations of the [MO4]n- complexes. On the basis of the analysis of Raman spectra, the effective use of crystals with the structure of sillenite in acousto‐optics is justified.

The absorption and circular dichroism spectra of Bi12SiO20and Bi12TiO20crystals codoped with Mn or Cr and a penta- (P5+), tri- (Ga3+), or divalent (Cu2+) element were studied. The results demonstrate that the sillenite crystals contain Mn and Cr in two oxidation states, 5+ and 4+. The introduction of P5+increases the fractions of Mn4+and Cr4+, while Ga3+and Cu2+have the opposite effect. The bands observed in the spectra are assigned to electronic transitions of [MnO4]4–and [MnO4]3–.