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

Abstract

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+). In the solid solution SrxBa1-xZn2Si2O7, also Zn(2+) can be replaced in a wide concentration range by other cations with the respective valency. In the present study, Zn was partially or completely replaced by Mg, Co, Mn, Ni, or Cu. If the high temperature phase is stable at room temperature, the thermal expansion is negative, and if the partial substitution exceeds a certain concentration threshold, the low temperature phase with the crystal structure of BaZn2Si2O7 and highly positive thermal expansion is formed. The lowest mean coefficients of thermal expansion were measured for the composition Ba0.5Sr0.5Zn1.4Co0.6Si2O7 with a value of -2.9 × 10(-6) K(-1). In general, a lower Zn-concentration leads to a higher anisotropy and a lower mean coefficient of thermal expansion.

Tuning Thermal Expansion in Metal–Organic Frameworks Using a Mixed Linker Solid Solution Approach

“…Construction of countless MOF topologies, using different metals (or metal clusters) and organic ligands, is possible . The preparation of solid solutions incorporating different ligands or metal clusters in a single-phase material enables fine-tuning of material properties, including thermal expansion. ,− Although NTE has been reported in a number of MOFs, , studies leveraging the modular buildup and controlled exchangeability of building blocks, or the preparation of solid solutions, to manipulate thermal behavior are scarce. , To our knowledge, there is no experimental evidence of tunable thermal expansion from negative to positive via the formation of MOF solid solutions in the peer-reviewed scientific literature, although there have been reports where the magnitude of thermal expansion has been tuned by incorporating guest molecules, isovalent metals, and structural defects. ,− …”

Structure and Crystallization of Alkaline-Earth Aluminosilicate Glasses: Prevention of the Alumina-Avoidance Principle

“…Research on aluminosilicate glass and glass–ceramic (GC) materials is of special interest owing to their many potential uses in photonics, optoelectronics, sealing, and biomedicine. − Aiming at broadening the scope of their technical applications, binary, ternary, and multicomponent systems have been investigated. − The capability of aluminosilicates to accept a wide range of oxides makes them very attractive for designing materials with tailor-made properties for specific applications. − When developing new glass materials by performing systematic changes in the chemical composition, it is necessary to define the noncrystalline structure of the primary glass and fluctuations occurring with changes in the composition in order to control the macroscopic properties. To this end, the use of suitable tools to assess the structural details and a specific structural model are required.…”

Negative Thermal Expansion in Ba0.5Sr0.5Zn2SiGeO7

“…The mean values of the respective CTEs are −2.2 × 10 −6 K −1 (30 °C–300 °C) and 0.9 × 10 −6 K −1 (30 °C–800 °C). These values are below those of the Ge-free compound Ba 0.5 Sr 0.5 Zn 2 Si 2 O 7 and also below the values of most compositions where Zn 2+ is replaced by other divalent transition metal ions or Mg 2+ exhibiting the same crystal structure [9]. …”

“…In the lower part, the theoretical peak positions of crystals with the structure of high-temperature (HT)- and low-temperature (LT)-BaZn 2 Si 2 O 7 taken from references [3,11] are displayed; ( b ) the lattice parameters of Ba 0.5 Sr 0.5 Zn 2 Si 2-x Ge x O 7 are shown as a function of x. The values for x = 0 were taken from reference [9]. …”

“…Especially in the case of phases with the structure of HT-BaZn 2 Si 2 O 7 , the CTEs of the different lattice parameters vary strongly [4,9]. The reason for this behavior is described in reference [3] to be caused by the crystal structure, which is composed of ZnO 4 chains, running through the crystal in the direction of the lattice parameter c. These chains are connected by Si 2 O 7 units.…”