Tuning negative thermal expansion in Bi1−<i>x</i> <i>Lnx</i>NiO3 (<i>Ln</i> = La, Nd, Eu, Dy)

Abstract

The compositional dependence of the negative thermal expansion (NTE) property of Bi1−xLnxNiO3 (Ln = La, Nd, Eu, Dy) was investigated. All x = 0.05 samples showed large NTE over αL = −70 ppm/K (αL: coefficient of linear thermal expansion) due to intermetallic charge transfer between Bi5+ and Ni2+. The temperature range of NTE shifted upward with decreasing ionic radius of Ln3+. Partial ordering of Bi/Ln is suggested to be the origin of this shift and the suppression of the broadening of the transition.