Abnormal Partial Dispersion in Pyrochlore Lanthanum Zirconate Transparent Ceramics

Abstract

We investigated the optical properties of La2Zr2O7 transparent ceramics and found that it showed abnormal partial dispersion. The origin of the abnormal partial dispersion was also investigated by measuring the vacuum ultraviolet reflectance and infrared absorption and by performing first‐principle calculations. All the measurements and calculations were also performed on LaAlO3–Sr(Al,Ta)O3 and Ba(Zr,Mg,Ta)O3 transparent ceramics, which showed normal dispersion, for comparison purposes. A comparison of the measurements and calculations with the numerical investigations carried out using a dispersion equation indicated that a weak intensity of absorption of La2Zr2O7 in the high energy region (20–30 eV) was thought to be the predominant reason for the abnormality. In addition, a narrower bandwidth of the O‐2p band of La2Zr2O7 resulted in a high intensity of absorption around 10 eV, which in turn resulted in a relatively low ratio of the intensity of absorption between 20 and 30 eV to the intensity of absorption around 10 eV. This narrower bandwidth of O‐2p was thought to augment the abnormality of La2Zr2O7.

Recent development of A2B2O7 system transparent ceramics

“…The refractive index of Y 2 Hf 2 O 7 , La 2-x Gd x Zr 2 O 7 , and Lu 2 Ti 2 O 7 was 2.018, 2.08, and 2.57, respectively. In 2012, Kintaka et al [103] reported the optical properties of La 2 Zr 2 O 7 transparent ceramic and its abnormal partial dispersion when performed for optical use. The origin of the abnormal partial dispersion was investigated by measuring the vacuum ultraviolet reflectance and infrared absorption and by performing first-principle calculations.…”

Y3NbO7 transparent ceramic series for high refractive index optical lenses

“…The refractive index and Abbe number data of several representative transparent ceramics are plotted in Figure 5, 3,[4][5][6]9,10 which show negative correlation. 3 The Y 1−x Nb x O 1.5+x transparent ceramic series (x = 0.20, 0.22, 0.24, 0.25, 0.26) with a defect fluorite structure were fabricated by a pressureless pre-sintering (1600°C for 10 h in air) and a HIP (1600°C for 1 h in 200 MPa argon) postsintering treatment.…”

“…3 Therefore, new transparent ceramic materials with a high refractive index are under development, such as Sr(Al 0.5 Ta 0.5 )O 3 (n = 2.01), 4 yttriastabilized zirconia (n = 2.23), 5 and La 2 Zr 2 O 7 (n = 2.09). 6 The A 2 B 2 O 7 7 and A 3 BO 7 8,9 transparent ceramic families (A = rare-earth metals, B = transition metal) generally possess a high refractive index. For example, La 2 Zr 2 O 7 , 6 Y 2 Ti 2 O 7 , 10 and Gd 3 TaO 7 9 transparent ceramics have a refractive index of 2.09, 2.29, and 2.0, respectively.…”

An overview on transparent ceramics with pyrochlore and fluorite structures

“…In 2012, La 2 Zr 2 O 7 transparent ceramics were reported in order to demonstrate their abnormal partial dispersion behavior. 58 High purity La(OH) 3 (99.99%) and ZrO 2 (99.99%) were mixed by using wet ball milling for 20 h. The mixture was dried and calcined at 1300 ○ C for 3 h. The calcined powder was remilled for 12 h in water, together with 0.004 wt.% SiO 2 as the sintering aid. Compacts from the mixed powder were calcined at 500 ○ C to remove the organic items, following CIP process at 600 MPa.…”