Zr1−xLnxW2O8−x/2 (Ln=Eu, Er, Yb): Solid solutions of negative thermal expansion-synthesis, characterization and limited solid solubility

Zr1−xLnxW2O8−x/2 solid solutions (Ln=Eu, Er, Yb) of different substitution fractions x have been synthesized. Their X-ray diffraction (XRD) patterns have been indexed and lattice parameters calculated based on the α-ZrW2O8 structure. The coefficients of thermal expansion (CTEs) of these solid solutions were estimated to be −10.3×10−6 K−1 in temperature range of 30–100 °C. The solubility of lanthanide ions in these solid solutions decreases linearly with the increase in the radius of substituted lanthanide ions. Based on the concentration dependence of phase transition temperatures, a novel method for determination of solubility of the lanthanide ions in Zr1−xLnxW2O8−x/2 solid solutions has been developed. This method seems to be more sensitive as compared with that based on XRD technique.