SPECTRAL AND ELECTRICAL PROPERTIES OF EUROPIUM-GALLIUM GARNET

FZBPGJ

Abstract

Particular attention of researchers to complex metal oxides with a garnet structure is associated with their widespread use in the chemical industry, micro- and optoelectronics. Rare earth garnets of the composition Ln₃M₅O₁₂, where M is Ga, Al or Fe, are used in solid-state lasers, microwave and ultrasonic devices, optical pressure sensors, as well as for the production of various types of ceramics, catalysts, radio- and anti-corrosion protective coatings and for some processing in the metallurgical and chemical industries. The synthesis of lanthanide gallates is a complex multi-stage process that uses high temperatures, mechanical activation of reagents, as well as repeated grinding of products followed by repeated annealing. Existing technologies are being improved, but their temperature characteristics remain consistently high. The authors of this work synthesized mixed oxide of europium and gallium by coprecipitation method from aqueous solutions of europium and gallium nitrates at a molar salt ratio of 3 : 5, as well as from compositions containing an excess of gallium salt, followed by annealing at a temperature of 800 °C for 24 hours. Technological hazards associated with the volatility of gallium compounds are identified and ways to eliminate them are shown. The composition and structure of the synthesis product were determined by chemical and X-ray phase analysis methods. The parameters of the crystal lattice have been determined: a = b = c = 1,2403 nm, true density 6.678 ± 0.006 g/cm³, active and reactive electrical resistance in the temperature range (25–150) °C when the frequency of the electric current changes from 50 Hz to 200 kHz. Based on the change in electrical characteristics, a conclusion was made about the semiconductor properties of the synthesized compound, which was confirmed by studying its luminescence. The luminescence of Eu₃Ga₅O₁₂ is associated with ⁵D_0,1 → ⁷F_j electronic transitions in Eu³⁺ ions. Excitation of luminescence occurs in the absorption bands of Eu³⁺, as well as result of their interaction with matrix components. In addition, a broad luminescence band with a maximum in the region of 450 nm was detected, associated with recombination processes at the levels of defects in the structure of Eu₃Ga₅O₁₂ after excitation as a result of the interband transition of electrons in europium gallate.