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Novel n-SrTiO₃/p-BiOI heterojunction composites were successfully fabricated by loading SrTiO₃ particles onto the surface of BiOI nanoflakes via a two-step method. The as-prepared samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FE-SEM), energy-disperse X-ray spectroscopy (EDS), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET), diffuse reflectance spectroscopy (DRS) and electrochemical measurements. The results show that the n-SrTiO₃/p-BiOI heterojunction composites are composed of perovskite structure SrTiO₃ and tetragonal phase BiOI. The composites exhibit excellent photocatalytic performance for the degradation of crystal violet (CV) solution under simulated solar light irradiation, which is superior to that of pristine BiOI and SrTiO₃. The 30wt.%SrTiO₃/BiOI composite is found to be the optimal composite, over which the dye degradation reaches 92.5% for 30min of photocatalysis. The photocatalytic activity of the 30wt.%SrTiO₃/BiOI composite is found to be 3.94 times and 28.2 times higher than that of bare BiOI and SrTiO₃, respectively. The reactive species trapping experiments suggest that $•{\mathrm{\text{O}}}_2^{-}$ and holes are the main active species responsible for the CV degradation. In addition, the electrochemical measurements elucidate the effective separation of photoinduced electron–hole pairs. Moreover, on the basis of experimental and theoretical results, a possible mechanism for the enhanced photocatalytic performance of the SrTiO₃/BiOI heterojunction composites is also proposed.

Structural, elastic, mechanical and electronic properties of pure and zinc-doped SrTiO₃ at the concentration in the range (1–10%) are studied by first-principles calculations. The structural parameters of synthesized compounds agree well with the standard data depicting the growth of stable compounds. A slight obvious increase in the lattice constant of 3.9245Å is observed in Zn-doped SrTiO₃ due to the deviation of the atomic radii of Zn and Ti. Elastic constants and mechanical parameters of SrTiO₃ are closer to their available theoretical and experimental data. The investigated compounds exhibit brittle behavior for all Zn ratios. The doping zinc concentration reduces the indirect band gap value. The doping concentration 2%, gives a band gap value closer to the experimental one. The band gap of pure SrTiO₃ is 1.827eV and after doping with Zn for concentration from 1% to 10%, the optimized values are 1.970, 1.886, 1.802, 1.718, 1.635, 1.552, 1.470, 1.389, 1.310, 1.231 and 1.154eV.

A novel strontium titanate/binary metal sulfide (SrTiO₃/SnCoS₄) heterostructure was synthesized by a simple two-step hydrothermal method. The visible-light-driven photocatalytic performance of SrTiO₃/SnCoS₄ composites was evaluated in the degradation of methyl orange (MO) under visible light irradiation. The photocatalytic performance of SrTiO₃/SnCoS₄-5% is much higher than that of pure SrTiO₃, SnCoS₄, SrTiO₃/SnS₂ and SrTiO₃/CoS₂. The SrTiO₃/SnCoS₄ composite material with 5wt.% of SnCoS₄ showed the highest photocatalytic efficiency for MO degradation, and the degradation rate could reach 95% after 140min irradiation time. The enhanced photocatalytic activity was ascribed to not only the improvement of visible light absorption efficiency, but also the construction of a heterostructure which make it possible to effectively separate photoexcited electrons and holes in the two-phase interface.

${\mathrm{\text{BaTiO}}}_3$/${\mathrm{\text{SrTiO}}}_3$ (BTO/STO) multilayer films were successfully prepared on (La, Sr)${\mathrm{\text{CoO}}}_3$-coated (100) ${\mathrm{\text{SrTiO}}}_3$ substrates by using a radio-frequency (RF) magnetron sputtering process at $700^{\circ }$C. Benefiting from the flexible deposition configuration of a multi-target sputtering system, we were able to tune the dielectric properties of the multilayer film by varying the number of multilayer periods $N$ and the individual layer thickness $d$. It was found that, in a superlattice-like structure ($d_{\mathrm{\text{BTO}}}=d_{\mathrm{\text{STO}}}$=4 nm, $\sim$ 10 unit cells), the dielectric constant increased and the loss tangent decreased with an increasing $N$, especially in the high frequency range ($10^4–10^6$Hz). This can be attributed to a reduced volumetric contribution to the dielectric property from the leaky interface capacitor layer, which lies between the multilayer film and the (La, Sr)${\mathrm{\text{CoO}}}_3$ electrode. On the other hand, as the individual layer thickness $d$ exceeds the superlattice limit ($d_{\mathrm{\text{BTO}}}=d_{\mathrm{\text{STO}}}$=8 nm, $\sim$ 20 unit cells), the superlattice strain effect disappeared and the dielectric constant value dropped by $\sim$50%. However, owing to the reduced number of interfaces and associated defects, the dielectric loss of the multilayer film with a larger period was reduced significantly, as compared to its superlattice counterpart with the same thickness and more periods. The dielectric loss power density of the former was about one order of magnitude lower than that of the latter. These observations provide a solid foundation for using RF magnetron sputtering as an effective method to prepare various forms of multilayer film capacitors for integrated device applications.