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

摘要

At thermal treatment of samples of potassium-aluminum-borate glass containing Cu and Br, a heterogeneous nanophase is formed as drops of the liquid containing CuBr and KBr. At room temperature, the phase contains CuBr and K2CuBr3 nanocrystals. The effect of sizes of nanophase areas on the temperatures of phase transformations (liquidus, solidus, and crystallization) at heating and cooling has been investigated. At the sizes of CuBr crystals equal to 10 nm, the solidus temperature is close to that shown on the state diagram of the KBr-CuBr system. The decrease of the sizes of CuBr crystals from 10 to 4.5 nm results in the decrease of the solidus temperature from 170 to 95A degrees C and the liquidus temperature from 208 to 120A degrees C: in other words, the dimensional effect is manifested almost identically on the values of the solidus and liquiddus temperatures. The decrease of the sizes of the liquid drops from 19 to 7 nm results in the decrease of the crystallization temperature from 100 to 70A degrees C.