(Bi,R)2O3 (R: Nd, Sm and Dy) oxides as potential pigments

Abstract In this work we have tackled the feasibility of the colored oxides in the Bi 2 O 3 –R 2 O 3 system as ecological inorganic pigments. We have prepared by solid state reaction the mixed oxides (Bi 2 O 3 ) 1− x (R 2 O 3 ) x , R: Nd, Sm and Dy, with nominal compositions: Nd, x =0.2 and 0.5; Sm, x =0.4; and Dy, x =0.35. The obtained orange (Bi 2 O 3 ) 0.6 (Sm 2 O 3 ) 0.4 and (Bi 2 O 3 ) 0.65 (Dy 2 O 3 ) 0.35 oxides present f.c.c. fluorite-type structure. (Bi 2 O 3 ) 0.8 (Nd 2 O 3 ) 0.2 oxide consists of a mixture of two phases which present f.c.c. δ-Bi 2 O 3 and Bi–Sr–O-type structures in the 900–1200°C temperature range. In the synthesis of the oxide with nominal composition (Bi 2 O 3 ) 0.5 (Nd 2 O 3 ) 0.5 we have obtained a greenish sample with higher neodymium content. This sample presents the Bi 3 R 5 O 12 -type structure. Diffuse reflectance data and color coordinates suggest that the (Bi 2 O 3 ) 0.6 (Sm 2 O 3 ) 0.4 and (Bi 2 O 3 ) 0.65 (Dy 2 O 3 ) 0.35 oxides are expected to be promising candidates as new ecological pigments.