Precipitation of nanosized crystals CuBr and CuCl in potassium aluminoborate glasses

Abstract

The precipitation of nanosized crystals CuBr and CuCl in potassium aluminoborate glasses con taining additives of jointly introduced Cu and Br, as well as Cu and Cl, respectively, has been studied by the methods of small angle X ray scattering (SAXS) and X ray powder diffraction (XRPD) analysis. It has been found that, upon thermal treatments at temperatures close to the glass transition temperature T g , halide phases precipitate in the form of liquid drops containing CuBr and KBr or CuCl and KCl. The presence of nanocrystals CuBr or CuCl, respectively, has been established in the samples at room temperature by the XRPD method. Liquidus, solidus, and crystallization onset temperatures in the regions of precipitated halide phases in heat treated glass samples have been determined from the temperature dependences of SAXS inten sity. The liquid released upon the heat treatment inside a matrix of potassium aluminoborate glass remains in the state of a supercooled liquid at temperatures essentially below the solidus temperature. At the drop sizes of the order of 10 nm, crystallization processes in them start at temperatures of 40-85°C.

Spectral properties of copper halide nanocrystals in glasses of fluorine-phosphate matrix

“…Spectrophotometric and X-ray diffraction studies proved the presence of the nanocrystals of desired composition in this dielectric matrix. The rather typical position of the absorption band of the Z 1,2 exciton of CuCl, which is indicated in the room-temperature absorption spectra of the glasses, is in agreement with data in the literature on inorganic glasses containing CuCl nanocrystals [5][6][7][8][9]. The twoband structure of the absorption spectrum clearly suggests the presence of spin-orbit splitting, which is characteristic of semiconductor nanocrystals and copper (I) chloride, in particular [9].…”

“…Based on the XRD data, one can estimate the linear size of nanocrystals of cubic modification. It is known [7] that this parameter can be calculated from the Debye-Scherrer formula ,…”

“…The results of XRD analysis of inorganic glasses based on silicate and borate matrices with CuCl nanocrystals [5,7] reveal the presence of a strong CuCl reflection at 2θ = 28.5° in the diffraction patterns of all previously known glasses. Thus, the presence of the reflection at an angle of 28.5°, which is typical of CuCl, definitely suggests the presence of nanocrystalline phase in glass, even in the absence of other reflections.…”

“…Glasses containing CuCl nanocrystals are characterized by high nonlinear optical response and photochromism [5,6]. Currently, it is known that the nanocrystalline copper halide phase segregates in glasses of borate [3,6,7] and silicate [5,8] matrices.…”

Effect of the size of CuBr nanocrystals formed in potassium-aluminum-borate glass on the phase transformation temperature

“…As shown by the method of X ray diffraction (XRD) analysis [1], nanosized crystals (NC) of CuBr were formed in copper containing potassium alumi num borate (PAB) glass with Br upon thermal treat ment.…”