Bi3+ doping in 1D ((CH3)3SO)PbI3: a model for defect interactions in halide perovskites

The recently described monodimensional hybrid pseudo-perovskites ((CH3)3SO)PbI3 exhibits complete Pb2+/Bi3+ miscibility in the B site. Heterovalent substitution imposes that charge-compensating defects are introduced in the lattice as well. This paper...

Investigation of the Heterovalent Substitution Cadmium for Lanthanum in Molybdate La2MoO6

This paper presents the investigation of the heterovalent substitution of cadmium for lanthanum in the La2-xCdxMoO6-x/2 system. The samples were synthesized by the solid state reaction method at 1000°C. The samples were characterized by X-ray powder diffraction with Rietveld refinements, scanning electron microscopy with energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy methods. The study results revealed that cadmium incorporation in the lanthanum molybdate leads to the transformation of the tetragonal structure of La2MoO6 to a cubic fluorite-like one. The content of the cubic phase reaches 94% in the Lа1.4Cd0.6MoO5.7 sample. The unit cell parameter of fluorite-like-phase decreases with cadmium content rising. The preferred location of cadmium ions in the cubic structure was established by the Rietveld refinement method. The heterovalent substitution cadmium for lanthanide in tetragonal La2MoO6 molybdate leads to the cubic fluorite phase stabilization in a similar way as it occurs in the process of reduction.

Synthesis of heterovalently substituted slab perovskites Sr2–xLnxBIV1–xBxIIIO4 (BIV= Sn, Ti, BIII= Sc, In)

The possibility of the heterovalent substitution of A- and B-positions atoms in a single-layer slab perovskite-like structure of strontium titanate and stannate Sr2BIVO4 (BIV= Ti, Sn) by type Sr2–xLnxBIV1–xBxIIIO4 (Ln == La – Tb, BIV= Ti, Sn, BIII= Sc, In) has been established by X-ray powder diffraction methods. The bounda-ries of the heterovalent substitution of A- and B-positions atoms and the crystallographic parameters of the synthesized Sr2–xLnxBIV1–xBxIIIO4 phases with a single-layer structure are determined. The continuous phase area formation with a single-layer structure has been observed in 10 systems: Sr2–xLnxTi1–xScxO4 (Ln = La, Pr, Nd, Sm, Eu), Sr2–xLnxTi1–xInxO4 (Ln = La, Pr), Sr2–xLaxSn1–xScxO4, Sr2–xLnxSn1–xInxO4 (Ln = La, Pr). In-creasing the degree of heterovalent substitution of atoms in these systems leads to a reduction of the sym metry of the crystal lattice of phases from the tetragonal (space group I4/mmm) to the interconnected rhombic one. In the rest of the studied Sr2–xLnxBIV1–xBxIIIO4 systems, the existence of a narrow (x value significantly less than 1) phase region with a single-layer structure based on Sr3BIVO7 is observed. The character of the phase relations in the Sr2–xLnxBIV1–xBxIIIO4 systems (Ln = La – Tb, BIII= Sc, In) (BIV= Sn, Ti) and the linear type of concentra-tion dependences of the parameters of the reduced tetragonal unit cells of Sr2–xLnxBIV1–xBxIIIO4 phases with a single-layer structure indicate that, by their nature, these phases are series of solid solutions in the pseudobinary systems Sr2BIVO4 – SrLnBIIIO4 (BIV= Ti, Sn, BIII = Sc, In). The obtained data can be used to regulate the functional properties of titanates and stannates Sr2BIVO4 and materials based on them, as well as to solve the problem of a purposeful search for new compounds of the type An+1BnO3n+1 with a slab perovskite-like structure.

Synthesis, structure and properties of solid solutions Ва1–хSn1+хF4 and (KyВа1–y)(1–х)Sn1+хF4–y(1–х)

We investigated the structure and electric conductivity of solid solutions of homovalent substitution Ва1–хSn1+хF4 (where х=0.03, 0.05, 0.07, 0.10, 0.15 and 0.23) and heterovalent substitution (KyВа1–y)(1–х)Sn1+хF4–y(1–х) (where х=0.03, 0.05, 0.10 and у=0.03, 0.05, 0.10) with the structure of BaSnF4. It was been found that the substitution of 7 mol.% of Ba2+ cations by Sn2+ cations contributed to an increases in electrical conductivity. The solid solution Ba0.77Sn1.23F4 had the highest electrical conductivity (573=6.8010–3 S cm–1). The substitution of barium ions by potassium ions in the BaSnF4 crystal lattice allowed reducing the conductivity of solid solutions regardless of the substituent content. Only the phases containing more than 3 mol.% of K+ ions exhibited the conductivity which exceeded the value of the initial phase at the temperatures above 385 K. In fluoride-conducting phases (KyBa1–y)(1–x)Sn1+xF4–y(1–х), the following solid solutions showed the highest electrical conductivity: (K0.05Ba0.95)0.97Sn1.03F3.95 (573=6.7810–4 S сm–1), (K0.03Ba0.97)0.95Sn1.05F3.97 (573=1.0010–3 S сm–1) and (K0.10Ba0.90)0.90Sn1.10F3.91 (573=8.7010–3 S сm–1).

The effect of local structure on the luminescence of Eu2+ in ternary phosphate solid solutions by cationic heterovalent substitution and their application in white LEDs

[Ca9Na3xY1−x(PO4)7 (0 ≤ x ≤ 1/2) ← Ca3(PO4)2 → Ca9+yNa3/2−y/2Y(1−y)/2(PO4)7 (0 ≤ y ≤ 1)] phosphors were achieved by cationic heterovalent substitution strategy.