Yttria single crystals (Y2O3) are important host materials for lasers. However, it high melting point (2450 ºC) is an experimental barrier for bulk crystal growth. Our main focus here was to study the influence of the sintering temperature and soaking time on the optical quality of the yttria ceramics due to the possibility to manufacture large pieces. The sintering process was performed in a radio-frequency furnace under dynamic vacuum. The heating system was efficient to reach temperatures up to 2000 ºC with heating rate higher than 100 ºC/min. The ceramics were prepared by solid state reaction using ZrO2 as additive. The maximum temperatures used in all experiments were from 1800 to 1900 ºC and soaking time kept between 1 h and 5 h. The optical transmission was measured in the visible-near infrared wavelengths interval and compared to the single crystalline fiber of the same composition, grown by the Laser-Heated Pedestal Growth (LHPG) technique in our labs. X-ray diffraction showed only yttria as single crystalline phase. Thus, all zirconia (up 3 mol%) was incorporated in the ceramic. Yttria transparent ceramics were fabricated with relative optical transparency when compared to single crystal. At 800 nm yttria transparent ceramics showed 60% of in-line optical transmission, what permit to be used in other optical applications, but is not sufficient as laser host material yet. However, our results are similar or better when compared to the literature and our experiments can be performed at a higher heating rate.
transparent ceramics; Y2O3; sintering; radio-frequency furnace
