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Bismuth silicate with sillenite structure (Bi 12 SiO 20 ) nanophase was prepared via melt–quenching technique in the Bi 2 O 3 –ZnO–SiO 2 glass system. The effect of replacement ZnO by Bi 2 O 3 was studied. Their thermal behavior showed the change of glass transition temperature (Tg) from 577 °C in the Bi 2 O 3 -free glass to 438 °C in ZnO-free glass. In addition, the crystallization temperatures were not only changed from two to one peak, but also decreased from 927 to 476 °C in the same order. According to the heat treatment regimes, willemite, sillenite, tetragonal Bi 2 O 3 , cubic Bi 2 O 3 and traces of ZnO were crystallized with different ratios depending on the change in composition and temperature. Sillenite was enhanced with increase heat treatment temperature and/or Bi 2 O 3 additions. Heat treatment at 650 °C/10 h revealed the best regime, where higher degree of crystallization was achieved. The microstructure at 700 ℃/30 min showed nano-scale oriented parallel rod crystals with hexagonal making at their end, whereas clusters of irregular nano-size crystals was appeared at 650 °C/10 h. Transmission spectra of the glasses in UV–Vis–midIR region were increased with Bi 2 O 3 addition reaching 74% in 100B. Photoluminescence properties of both glasses and their corresponding glass–ceramics showed luminescence nature since the blue and green colors were clearly appeared. Calculation of optical bandgap (E opt ) revealed 3.2–2.19 eV with increasing Bi 2 O 3 ; these values are located in the semiconducting range. The prepared samples can be utilized in electro-optical instruments, also the high transmission in mid-IR nominate it for IR transmitting windows.

Using a non-holographic optical setup, we employed a Mueller–Stokes polarimeter to measure both the linear electro-optic and second-order electrogyration effects. The second-order electrogyration effect was observed in a B i 12 S i O 20 (BSO) crystal with a (110) cut. This response was found for the electric field applied both parallel and perpendicular to the [001] direction, where the values for the second-order electrogyration are 4.86 × 10 7 pm 2 / V 2 and 1.87 × 10 7 pm 2 / V 2 , respectively. Additionally, the linear electro-optic coefficient γ 41 was measured to be 1.17 pm/V for 660.5 nm .

Undoped, 0.5, 1.0, and 2.0% Nd-doped Bi4Si3O12 (BSO) crystals were synthesized by the floating zone method. Regarding photoluminescence (PL) properties, all samples had emission peaks due to the 6p–6s transitions of Bi3+ ions. In addition, the Nd-doped samples had emission peaks due to the 4f–4f transitions of Nd3+ ions as well. The PL quantum yield of the 0.5, 1.0, and 2.0% Nd-doped samples in the near-infrared range were 67.9, 73.0, and 56.6%, respectively. Regarding X-ray-induced scintillation properties, all samples showed emission properties similar to PL. Afterglow levels at 20 ms after X-ray irradiation of the undoped, 0.5, 1.0, and 2.0% Nd-doped samples were 192.3, 205.9, 228.2, and 315.4 ppm, respectively. Dose rate response functions had good linearity from 0.006 to 60 Gy/h for the 1.0% Nd-doped BSO sample and from 0.03 to 60 Gy/h for the other samples.

The effect of optical activity on the linear and circular bulk photovoltaic effect in crystals without a center of symmetry is investigated. It is shown that there is a phase shift of the linear photovoltaic current JL, which is opposite for the right- and left crystals, and a change in modulus. The circular photovoltaic current JC does not change in phase in dependence of the optical activity value but depends on the absorption and circular dichroism. The dependences of the JL current on the polarization of incident light are calculated taking into account the optical activity for the right and left Bi12SiO20, Bi12GeO20, and Bi12TiO20 crystals (class 23). Similar calculations of JL were performed for the right crystals Pb5Ge3O11 (class 3); La3Ga5SiO14 with impurities of Pr, Fe, Cr, and Mn, Ca3TaGa3Si2O14 (class 32); and Er(HCOO)3⋅2H2O (class 222) in the case where light propagates in the direction of the optical axis. Examples of the JC value for crystals Pb5Ge3O11; La3Ga5SiO14 with of Co, Cr, and Fe impurities; and α-HgS (class 32) are given. It is shown that consideration of optical activity is necessary when studying the photorefractive effect in crystals.

This study presents a thorough examination of the structural and thermal characteristics of Bi 12 SiO 20 crystal. X-ray diffraction (XRD) analysis was employed to investigate the crystallographic structure, while scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were utilized to ascertain morphological features and elemental composition, respectively. The XRD spectrum exhibited numerous peaks corresponding to the cubic crystalline structure. Thermal behavior was investigated through thermal gravimetric analysis (TGA), differential thermal analysis (DTA) and differential scanning calorimetry (DSC). Within the crystal, negligible weight loss was observed up to 750 °C, followed by weight loss processes occurring in the temperature ranges of 750–919 °C and above 919 °C. The 2% weight loss in the range of 750–919 °C was associated with the decomposition process, and the activation energy of this process was found to be 199 kJ/mol considering Coats-Redfern expression. A significant weight loss was observed in the region above 919 o C and was associated with the decomposition of the Bi 12 SiO 20 compound and/or the melting processes of the components of the Bi 12 SiO 20 compound. Three endothermic peaks were observed in the DTA plot. Additionally, DSC measurements conducted under varied heating rates indicated endothermic crystallization process around 348 °C, with an activation energy of 522 kJ/mol determined through the Kissenger equation. These findings present valuable details regarding the crystal’s structural configuration, morphological attributes, and decomposition/phase transitions, thereby illuminating its potential applications across various fields.

In this work, a new approach to the preparation of heterostructured nanoparticles (NPs) based on bismuth silicates Bi2SiO5/Bi12SiO20 is proposed and implemented. This approach is based on solid-phase synthesis by annealing of a pre-homogenized mixture of β-Bi2O3 and SiO2 powders in different ratios. For this purpose, industrial silica nanopowder and β-bismuth oxide NPs powder obtained by pulsed laser ablation (PLA) in air are used. The morphology, phase composition and optical properties of the obtained materials are studied. By changing the ratio of precursors, the powders similar in structure to single-phase bismuth silicates Bi2SiO5 and Bi12SiO20 was well as heterostructured NPs on their basis are obtained. The activity of the photocatalysts in the reactions of Rhodamine B (Rh B) decomposition and selective oxidation of 5-hydroxymethylfurfural (5-HMF) is estimated. The best photocatalytic activity is demonstrated by powders with a similar Bi2SiO5/Bi12SiO20 (or 4Bi: 1Si) phase ratio. As a result of the analysis of the data obtained, the formation of a type II heterojunction is proposed.

A novel Z-scheme Bi 2 MoO 6 /Bi 12 SiO 20 (MS) heterojunction, with 2D nanoplates of Bi 2 MoO 6 anchored on the surface of flower-shaped Bi 12 SiO 20 particles, was synthesized via simple solvothermal process for the first time. A series of techniques including XRD, XPS, SEM, TEM, BET, UV–vis DRS and Mott–Schottky were used for characterizing the photocatalysts. The MS 0.6 (the heterojunction with a Bi 2 MoO 6 /MS mass ratio of 0.6:1) exhibited optimal photocatalytic activity for degrading RhB, and the reaction rate constant achieved 0.041 min −1 , which was 41 and 4.6 times that of Bi 12 SiO 20 and Bi 2 MoO 6 , respectively. The MS 0.6 also presents outstanding activity for the degradation of BPA (0.014 min −1 ), which was 3.5 and 14 times that of Bi 12 SiO 20 and Bi 2 MoO 6 , respectively. Furthermore, the UV–vis absorption spectrum and TOC test confirmed that the mineralization capacity of Bi 2 MoO 6 was significantly enhanced after coupling with Bi 12 SiO 20 . The enhanced performance was attributed to the improved light absorption and excellent separation efficiency of photo-induced carriers. Trapping and ESR experiments indicated that h + and •O 2 − jointly dominated the degradation of RhB. Therefore, a reliable Z-scheme mechanism was proposed. Additionally, MS 0.6 presented a good stability and durability in four catalytic runs. This study provides an insight for designing highly efficient Z-scheme Bi 12 SiO 20 -based photocatalysts for the practical sewage disposal. Graphical abstract

A series of Bi 4 Si 3 O 12 :Dy 3+ phosphor have been synthesized via conventional solid-state reaction method and its luminescence properties were investigated as near cool white light emitting and long afterglow phosphor. Crystal structure and phase structure characterization is determined using X-ray diffraction (XRD), SEM and EDS. Rietveld structural refinement and XRD confirms that prepared sample exhibit pure cubic structure [space group I-43d]. Photoluminescence spectra of both doped and undoped Bi 4 Si 3 O 12 phosphor were efficiently excited in the range of 200-450 nm, and prepared phosphor under 272 nm excitation exhibit three emission peaks located at 463 nm(blue), 482 nm(blue) and 576 nm (yellow) corresponding to 3 P 1  →  1 S 0 , 4 F 9/2  →  6 H 15/2 and 4 F 9/2  →  6 H 13/2 transitions. Characteristic emission peaks of Dy 3 + centered at 482 nm and 576 nm were assigned for white light emission. The calculated Commission Internationale de I’Eclairage (CIE) chromaticity confirms that with Dy 3+ doping, the luminescence co-ordinates of Bi 4 Si 3 O 12 phosphor shift to near white( x  = 0.316, y  = 0.358) region which is close to commercial pc-LED (Blue LED + YAG:Ce 3+ ) ( x  = 0.320, y  = 0.320) co-ordinates. Computation of correlated color temperature 6184 K endorses that prepared phosphor is cool in nature and can be served as white light emitting phosphor. Comparative thermoluminescence study of UV and γ-irradiated Bi 4 Si 3 O 12 :Dy 3+ phosphor is performed for the dosimetry application. TL intensity is recorded maximum at 30 min under UV irradiation (256 nm), and for γ irradiation, it was recorded at 10 kGy dose rate. γ-irradiated Bi 4 Si 3 O 12 :Dy 3+ phosphor TL study is reported for the first time at different dose rate and concentration for high dosimetry application. The defect characteristic is examined, Trap depths and other kinetic parameters are also evaluated by Chen’s peak shape method. Decay and fading measurement under UV/γ irradiation are performed to examine the long after glow properties of prepared samples. TL emission spectrum studies are also performed.

The sillenite compound Bi 12 SiO 20 was synthesized via Pechini sol–gel method. Composition, crystallinity, microscopic appearance, and optical properties of samples were characterized by XRD, SEM, FTIR, and UV/Vis/NIR spectrophotometer. The photocatalytic property of pure Bi 12 SiO 20 was also investigated by detecting the degradation rate of rhodamine B (RhB). The experimental conditions related to the preparation of pure phase bismuth silicate, such as the content of citric acid, calcination temperature schedule, and the molar ratio of Bi/Si were investigated. And when n (citric acid)  = 13 mmol, n (Bi/Si)  = 10, and heat preservation at 630 °C for 5 h, pure bismuth silicate powder can be successfully synthesized. And the degradation of RhB by Bi 12 SiO 20 under visible light for 150 min can reach to 80%, which indicated that pure Bi 12 SiO 20 is an excellent photocatalyst under the visible light. In addition, the capture experiments demonstrate that (V o + ) dominates in photocatalytic degradation. Highlights Pure Bi 12 SiO 20 photocatalyst can be successfully synthesized by Pechini method. Bi 12 SiO 20 has a typical sillenite structure with the band gap of 2.4 eV. Bi 12 SiO 20 shows a better visible-light photocatalytic performance than P25.

The hard agglomeration of bismuth silicate prepared by sol–gel method is the main reason to hinder its modification, photocatalytic performance and application. In order to better improve the photocatalytic performance of photocatalysts, polystyrene (PS) spheres modified Bi 12 SiO 20 –Bi 2 O 2 SiO 3 composites (PBSO) and silver-loaded PS spheres modified BSO composites (Ag-PBSO) are prepared by PS spheres and photoreduction method. The crystal phase, morphology and optical properties of the catalysts were characterized by XRD, SEM and UV–Vis DRS, respectively. The visible light degradation activity of the photocatalysts is analyzed via ultraviolet-visible spectrophotometer. The results show that the Ag-PBSO photocatalyst can degrade more than 97% of the pollutants within 75 min. This is attributed to the synergy of heterojunction, specific surface area and SPR effect. Among them, after the introduction of PS template, the structure becomes loose and the specific surface area increases. This greatly increases the contact area of the catalyst with pollutants, providing a more robust loading environment for the subsequent Ag. In addition, the SPR effect possessed by Ag can synergize with the large specific surface area to accelerate electron transfer between heterojunctions. This method provides a new idea for the degradation of organic pollutants in the environment.