Cracks in transparent La-doped yttria ceramics and the formation mechanism

Fabrication of transparent La-doped Y2O3 ceramics using different La2O3 precursors

“…The Y 2 O 3 and La 2 O 3 powders were calcined at 800 • C to remove possible absorption and kept in a desiccator before usage. Powders with the designed formula (Y 94 La 6 ) 2 O 3 were weighed immediately after their removal from the desiccators so as to maintain constant weight over a short time [11]. The weighted powders were ball milled in zirconia jars using a planetary milling machine for 24 h at a rotation speed of 256 rpm (rotation per minute).…”

“…The use of La 2 O 3 permits the attainment of ceramics with high optical quality and good mechanical properties by eliminating pores and inhibiting grain growth during the Y 2 O 3 ceramic sintering process [8][9][10]. However, La 2 O 3 rapidly absorbs moisture and carbon dioxide from air to form hydroxides and hydroxycarbonates [11,12], which makes it more difficult to maintain an exact weight during the weighing process. The absorption of H 2 O and CO 2 leads to a weight increase and composition variation, resulting in the fluctuation of the sintering behavior and refractive index, among others [4].…”

“…The absorption of H 2 O and CO 2 leads to a weight increase and composition variation, resulting in the fluctuation of the sintering behavior and refractive index, among others [4]. In order to insulate against H 2 O and CO 2 absorption, such procedures have to be carried out under N 2 , which increases the production cost, especially in the case of industrial production [11].…”

“…The corresponding calculated results are 10.62532 Å, 10.62739 Å and 10.62891 Å, which are larger than that of pure Y 2 O 3 (10.604 Å), demonstrating the substitution of larger La 3+ ions (R = 1.06 Å) to Y 3+ ions (R = 0.89 Å)[19] and the formation of a La 2 O 3 -Y 2 O 3 solid solution. As Mao et al[11] noted, La 2 O 3 diffusion decreases the humidity absorption capability of the Y 2 O 3 lattice, which is favorable for the sintering of large-sized transparent ceramics as it avoids the formation of cracks.The sintering behavior of the samples doped with La 2 O 3 , La(OH)3 and La 2 O 2 CO 3 is presented in the sintering shrinkage curves shown inFig. 7.…”

TUNING THE OPTICAL AND MECHANICAL PROPERTIES OF Y2O3 CERAMICS BY THE INCLUSION OF La3+ ION IN THE MATRIX FOR INFRARED TRANSPARENT WINDOW APPLICATIONS

“…The ionic radius of La 3+ (1.032 A o ) is larger than that of Y 3+ (0.90 A o ) ions [22]. As the La 3+ concentration increases the diffraction peaks shift towards shorter 2θ side which attributes to the increase in d-spacing due to the substitution of bigger La 3+ ion in the Y 3+ sites [16,23]. Table 1 shows the variation in d-spacing and cell parameters for the (222) peak with increasing La 3+ ion concentration.…”