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Mixed‐halide perovskites show promising applications in tandem solar cells owing to their adjustable bandgap. One major obstacle to their commercialization is halide phase segregation, which results in large open‐circuit voltage deficiency and J‐V hysteresis. However, the ambiguous interplay between structural origin and phase segregation often results in aimless and unspecific optimization strategies for the device's performance and stability. An atomic scale is directly figured out the abundant Ruddlesden‐Popper anti‐phase boundaries (RP‐APBs) within a CsPbIBr2 polycrystalline film and revealed that phase segregation predominantly occurs at RP‐APB‐enriched interfaces due to the defect‐mediated lattice strain. By compensating their structural lead halide, such RP‐APBs are eliminated, and the decreasing of strain can be observed, resulting in the suppression of halide phase segregation. The present work provides the deciphering to precisely regulate the perovskite atomic structure for achieving photo‐stable mixed halide wide‐bandgap perovskites of high‐efficiency tandem solar cell commercial applications. [ABSTRACT FROM AUTHOR]

Uncovering an efficient and stable photocatalytic system for seawater splitting is a highly desirable but challenging goal. Herein, Cd0.2Zn0.8S@Silicalite-1 (CZS@S-1) composites, in which CZS is embedded in the hierarchical zeolite S-1, were prepared and show remarkably high activity, stability and salt resistance in seawater. [ABSTRACT FROM AUTHOR]

La2O3 and Nd2O3 were used to substitute Bi2O3 and the effects of complex substitution on the sintering behavior and the microwave dielectric properties of BiNbO4 ceramics were studied. With 0.5 wt.% CuO–V2O5 mixtures addition, all of the Bi1−x(La0.38Nd0.62)xNbO4 ceramics could be densified below 920 °C. The triclinic phases are identified in Bi1−x(La0.38Nd0.62)xNbO4 ceramics with x=0.01 sintered at 820 °C and the triclinic intensities increase with increasing the x value and sintering temperature. The saturated bulk density slightly decreases from 7.17 to 7.13 g/cm3 and the ϵr value from 44.24 to 42.76 with increasing x from 0 to 0.07 for Bi1−x(La0.38Nd0.62)xNbO4 ceramics. The saturated Q×f value is between 10,300 and 12,400 GHz depending on the x value. The τf values of dense Bi1−x(La0.38Nd0.62)xNbO4 ceramics decrease from 28.32 to 12.79 ppm/°C with x varying from 0 to 0.01 and remain almost unchanged with further increasing x. [Copyright &y& Elsevier]

β-BiNbO4 powder with nanometer sized (≈65 nm) particles was prepared by citrate sol–gel technique. Using Bi-citrate and Nb-citrate as the starting precursors, the crystalline phase of β-BiNbO4 could be obtained by thermal decomposition of citrate complex precursors at a low temperature (600 °C). Infrared spectrum, thermogravimetry–differential thermal analysis (TG–DTA), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) technique and transmission electron microscopy (TEM) were used to characterize the citrate precursors and the calcined powders. [Copyright &y& Elsevier]

Effects of Ta substitution for Nb on the microwave dielectric properties of BiNbO4 ceramics have been investigated. BiNb(1−x)TaxO4 (x=0, 0.1, 0.2, 0.3, 0.4) with 0.3 wt.% CuO–V2O5 mixtures addition can be densified at very low sintering temperature below 860 °C. The dielectric constants (ϵr) of the Ta-modified BiNbO4 ceramics increase with increasing of Ta contents, but the Q×f values have no apparent changes. The temperature coefficient of resonant frequency (τf) changes from positive to negative with change of x values. The crystalline phase and microstructure of Ta-modified BiNbO4 ceramics have been characterized by X-ray diffraction and scanning electron microscopy respectively. [Copyright &y& Elsevier]

Sb2O5 were selected to substitute Nb2O5 and the effects of substitution on the sintering behavior and the microwave dielectric properties of BiNbO4 ceramics were studied. Solid solutions formed in sintered BiNb(1−x)SbxO4 ceramics with x value being no more than 0.4. The unit cell volume of orthorhombic phase BiNb(1−x)SbxO4 decreased from 331.86 to 324.99 A˚3 with x value increasing from 0 to 0.4. The densified temperatures increased from 800 to 940 °C. The microwave dielectric properties of BiNb(1−x)SbxO4 ceramics were found to be affected by the substitution of Sb for Nb and the sintering temperature. The saturated ϵr values first increased from 44.00 to 44.61 with x increasing from 0 to 0.1 and then decreased to 40.69 with x to 0.4. The saturated Q×f values decreased with increasing of x value. The τf values were correlated to the unit cell volume of BiNb(1−x)SbxO4 and continuously decreased from a positive value of 14.19 ppm/°C for x=0 to a negative value of −30.94 ppm/°C for x=0.4. At a sintering temperature of 820 °C and x value of 0.05, BiNb(1−x)SbxO4 ceramics exhibited the optimum microwave dielectric properties of ϵr ∼ 44.49, Q×f ∼ 14,278 GHz, and τf ∼ −5.19 ppm/°C. [Copyright &y& Elsevier]

We report on the observation of an orthorhombic ferroelectric phase in 0.67Pb(Mg[sub 1/3]Nb[sub 2/3])O[sub 3]-0.33PbTiO[sub 3] single crystals, whose polarization is along <011> direction and stability can be altered by poling conditions. We studied the piezoelectric properties on poled <011> crystals, in both monodomain and polydomain states, and found that the piezoelectric d[sub 32] coefficient, which is the piezoelectric response in perpendicular to the poling direction, is positive in both cases. Based on the phenomenological theory, we show that this is possible in a crystal with the electrostrictive coefficients Q[sub 11]>Q[sub 44]-Q[sub 12]. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]