The present disclosure is related to systems and methods for solid-phase reactions.

A halide producing method according to the present disclosure includes heat-treating a material mixture that is a material containing an MO.sub.x powder and an NH.sub.4X powder in an inert gas atmosphere or in a vacuum. M represents at least one element selected from the group consisting of rare-earth elements, X represents at least one element selected from the group consisting of F, Cl, Br, and I, x is greater than or equal to 1 and less than or equal to 2, and Requirement (a) or Requirement (b) below is satisfied,

D1?D2 and D2?D1?0.5?D2(a)

D2<D1 and D1?D2?0.5?D1(b)

where an average particle diameter of the MO.sub.x powder is denoted by D1, and an average particle diameter of the NH.sub.4X powder is denoted by D2.

Lanthanide double perovskite nanocrystals are described. The nanocrystals display high energy luminescence, making them useful in a variety of light-emitting materials and devices. Methods of preparing the lanthanide double perovskite nanocrystals using a hot injection method are also described.

Lanthanide double perovskite nanocrystals are described. The nanocrystals display high energy luminescence, making them useful in a variety of light-emitting materials and devices. Methods of preparing the lanthanide double perovskite nanocrystals using a hot injection method are also described.

The solid electrolyte material contains a halide solid electrolyte. The halide solid electrolyte contains Li, at least one element selected from the group consisting of metalloids and metal elements other than Li, and at least one element selected from the group consisting of F, Cl, Br, and I. The halide solid electrolyte has a crystallite size greater than or equal to 40 nm.

The solid electrolyte material contains a halide solid electrolyte. The halide solid electrolyte contains Li, at least one element selected from the group consisting of metalloids and metal elements other than Li, and at least one element selected from the group consisting of F, Cl, Br, and I. The halide solid electrolyte has a crystallite size greater than or equal to 40 nm.

A solid electrolyte of the present disclosure contains Li, M, and X, and, in the solid electrolyte, the coefficient of variation of the M content is 10 or less, and the coefficient of variation of the X content is 15 or less. A method for producing a solid electrolyte according to the present disclosure includes (A) synthesizing a halide containing Li, M, and X, (B) pulverizing the halide, and (C) heat-treating the halide, and the (A), the (B), and the (C) are performed in this order. Here, M is at least one selected from the group consisting of metalloids and metal elements other than Li, and X is at least one selected from the group consisting of F, Cl, Br, and I.

A solid electrolyte of the present disclosure contains Li, M, and X, and, in the solid electrolyte, the coefficient of variation of the M content is 10 or less, and the coefficient of variation of the X content is 15 or less. A method for producing a solid electrolyte according to the present disclosure includes (A) synthesizing a halide containing Li, M, and X, (B) pulverizing the halide, and (C) heat-treating the halide, and the (A), the (B), and the (C) are performed in this order. Here, M is at least one selected from the group consisting of metalloids and metal elements other than Li, and X is at least one selected from the group consisting of F, Cl, Br, and I.

Provided is an electrode active material for a fluoride ion battery. The electrode active material for a fluoride ion battery includes a complex oxide that comprises a melilite-type crystal structure. The complex oxide includes: a first metal atom that comprises at least one type selected from a first metal atom group; a second metal atom that comprises at least one type selected from a second metal atom group; a specific non-metal atom that comprises at least one type selected from a specific non-metal atom group; and at least an oxygen atom as the specific non-metal atom. The first metal atom group includes Li, Be, Na, Mg, K, Ca, Rb, Sr, Y, Cs, Ba, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Bi. The second metal atom group includes Al, Si, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Sn, Hf, Ta, W, Re, Os, Ir, Pt, and Au. The specific non-metal atom group includes O, F, N, S, and Cl.

A solid ion conductor compound including Li, Ho, and a halogen element, wherein the compound has diffraction peaks at 30?2? to 33?2?, 33?2? to 36?2?, 40?2? to 44?2?, and 48?2? to 52?28?, when analyzed using CuK? radiation, and wherein a full width at half maximum of at least one peak at 40?2? to 44?2? is 0.3?2? or greater.