Chemical bond characteristics, thermal expansion property and compressibility of AR 2O 4 (A = Ca, Sr, Ba; R = rare earths)

Abstract

Theoretical researches were performed on the CaFe 2O 4-type binary rare earth oxides AR 2O 4 (A = Ca, Sr, Ba; R = rare earths) by using chemical bond theory of dielectric description. The chemical bond properties of these crystals were explored, and then the thermal expansion property and compressibility were studied. The theoretical values of linear thermal expansion coefficient (LTEC) and bulk modulus were presented. The calculations revealed that the LTECs and the bulk moduli do have linear relationship with the ionic radii of the rare earths. In the cases of Sc and Y, both the LTEC and bulk modulus values are larger than the lanthanide series. We attribute this to the difference in the electronic configuration between Sc (Y) and lanthanide series. For SrY 2O 4 and BaY 2O 4 crystals, the theoretical values of LTEC and bulk modulus agree well with experimental ones.