New Family of Materials with Negative Coefficients of Thermal Expansion: The Effect of MgO, CoO, MnO, NiO, or CuO on the Phase Stability and Thermal Expansion of Solid Solution Phases Derived from BaZn2Si2O7.

Recently, a silicate with the composition SrxBa1-xZn2Si2O7 was reported, which exhibits a negative coefficient of thermal expansion. The compound BaZn2Si2O7 shows a highly positive coefficient of thermal expansion up to a temperature of 280 °C and then transfers to a high temperature phase, which exhibits a coefficient of thermal expansion near zero or negative over a limited temperature range up to around 500 °C. This high temperature modification can be stabilized to room temperature if Ba(2+) is replaced by Sr(2+).