Impact of high-temperature sintering on SiO 2 − LiO 2 − Al 2 O 3 − K 2 O − P 2 O 5 ${\rm SiO}_2{-}{\rm LiO}_2{-}{\rm Al}_2{\rm O}_3{-}{\rm K}_2{\rm O}{-}{\rm P}_2{\rm O}_5$ glass ceramics with ZrO 2 ${\rm ZrO}_2$ and Y 2 O 3 ${\rm Y}_2{\rm O}_3$ additives

Abstract

The influence of multi-step sintering at high temperatures was used to meticulously characterize the crystallization, mechanical, and optical properties of a ${\mathrm{SiO}}_2-{\mathrm{Li}}_{2}O-{\mathrm{Al}}_2{O}_3-K_{2}O-P_2{O}_5$ glass system with the addition of ${\mathrm{ZrO}}_2$ and $Y_2$$O_3$. The research began with a novel base glass composition of 3.8 wt% ${\mathrm{Li}}_2$${\mathrm{CO}}_3$, 4.2 wt% $K_2$${\mathrm{CO}}_3$, 4.5 wt% ${\mathrm{Al}}_2$$O_3$, 35 wt% ${\mathrm{SiO}}_2$, and 2.5 wt% ${\left({\mathrm{NH}}_4\right)}_2$${\mathrm{HPO}}_4$, to which 47 wt% ${\mathrm{ZrO}}_2$ and 3 wt% $Y_2$$O_3$ added. The initial glass powder was sintered in two steps at low temperatures. Either 500${}^{\circ }C$ for 10 min or 500${}^{\circ }C$ for 10 min then a raise to 650${}^{\circ }C$ for 20 min was used in the first step. Then, the second step of sintering was done at 850${}^{\circ }C$. Finally, after the pellet preparation, final calcination was conducted at 1450${}^{\circ }C$. The resulting microstructure was a composite material with various grain components embedded within a glass matrix. The low first sintering temperature triggered the optimum crystal growth, and after the final calcination process, a new glass-ceramic named ${\mathrm{ZrSiO}}_4-{\mathrm{ZrO}}_2-{\mathrm{Zr}}_{0.95}{Y}_{0.066}{O}_{1.985}$–$\mathrm{LiAl}{\left({\mathrm{SiO}}_3\right)}_2$ was synthesized. The synthesized ceramics demonstrated strong diametral tensile strength and excellent Vickers micro-hardness values, a remarkable refractive index, and optical band gaps larger than 3.1 eV. Consequently, the process of multi-step sintering at high temperatures clenches the impending manufacture of a novel composite ceramic having remarkable hardness and good optical properties that encourage several biological, technological, and industrial applications.