Luminescence properties of ZrO2-CaO eutectic crystals with ordered lamellar microstructure activated with Er3+ ions

Er3+-doped ZrO2-CaO eutectic crystals with ordered microstructure have been grown by the laser floating zone method. The microstructure consists of alternating 2 mu m thick lamellae of calcia-stabilized zirconia (CaSZ) and CaZrO3 crystals. Er3+ enters both phases but at a higher concentration in CaSZ. Due to its higher refractive index, the latter phase acts as a light guiding medium. The optical properties of Er3+-doped eutectic, as well as its components, CaSZ and CaZrO3 crystals, are analyzed. Absorption and emission spectra of CaZrO3 consist of narrow bands. For this crystal most of the Er3+ Stark level positions are given. In contrast, the bands for CaSZ are broad, as it corresponds io a defective material. Absorption oscillator strengths, radiative-transition probabilities and emission lifetimes have been measured at different temperatures, between 600 and 4 K. Absorption oscillator strengths are 1.5 times higher for Er3+ in CaZrO3 than in CaSZ, while multiphonon deexcitation probabilities are one order of magnitude smaller, with the exception of the lowest energy I-4(13/2)-->I-4(15/2) emission, which presents the maximum quantum efficiency in both phases. [S0163-1829(97)02342-4].