Dariya E. Deulina

Subject of study. This study focuses on multilayer yttrium aluminum garnet/yttria-stabilized zirconia (YAG/YSZ) ceramics doped with rare earth ions. Aim of study. The aim of this study is to produce luminescent multilayer ceramics composed of YAG:CeO₂/YSZ:Eu₂O₃ with an increased shape factor using the spark plasma sintering technique and to investigate their complex optical-luminescent characteristics, which have potential applications as radiation converters. Method. The functionally graded ceramic samples were fabricated using the spark plasma sintering technique. The morphology and spectral-luminescent properties of the materials were analyzed through electron microscopy, photoluminescence, and cathodoluminescence spectrometry. Main results. The study demonstrates the feasibility of producing luminescent multilayer ceramics with the YAG:CeO₂/YSZ:Eu₂O₃ composition via the spark plasma sintering technique, achieving an increased shape factor. The dynamics of relative shrinkage were examined, revealing that the sintering parameters (temperature of 1450°C, pre-pressure of 80 MPa, and isothermal exposure duration of 30 min) are sufficient to obtain relatively dense multilayer ceramics of the selected composition. Studies on the spectral characteristics of YAG/YSZ functionally graded ceramics doped with europium and cerium oxides identified the main types of luminescence centers and elucidated the mutual influence of different layers on the luminescent properties. The integrated cathodoluminescence and photoluminescence spectra were consistent with existing theories regarding luminescence centers in YAG and YSZ materials, confirming the success of the sintering process. Practical significance. The comprehensive analysis of YSZ/YAG multilayer ceramics doped with rare earth ions conducted in this study demonstrates their potential use as converters of high-power laser radiation.

Magnesium aluminate spinel is a promising material for optical application. It can be used as transparent armor, spacecraft windows, scanners, optical elements in night vision systems, as well as a base (matrix) for scintillation and laser materials. The wide range of practical applications of MgAl2O4 ceramics is due to the complex of its unique properties. The research is aimed to creating transparent ceramic materials with an increased shape factor, relevant and of high practical importance. In the presented work, a comprehensive characterization of the commercial nanopowder of magnesium aluminate spinel is completed. Its main structural features are defined. Rheological properties of nanopowder in the process of its compression and thermal consolidation are investigated on the basis of the provisions of the mechanistic pressing model by approximating experimental data of compaction during spark plasma sintering with a dimensionless logarithmic equation, the graphical representation of which allows us to evaluate the possibility of achieving a non-porous state of the consolidated material and optimize the modes of spark plasma sintering. Shown, that the structure of the sealing surface and the search for the optimal way to increase pressure and temperature during spark pulse plasma sintering on this surface can be used to optimize the consolidation modes of transparent ceramics. Verified discrete element modeling of the processes of packing and consolidation of particles of magnesium aluminate spinel nanopowder has been performed. Model and field experiments have shown that the revealed combination of temperature (1300 °C) and static pressure (100 MPa) is sufficient to obtain a porous ceramic structure and does not lead to excessive recrystallization. It is shown that transparent ceramics based on magnesium aluminate spinel with an increased shape factor can be produced by spark plasma sintering at temperature of 1300 °C and static pressure of 100 MPa. The optical and mechanical properties of the manufactured transparent ceramics are comparable to their analogues. The light transmission of samples reaches 41% of the visible spectrum and 64% in the infrared spectrum, the Vickers microhardness value is 15.6±0.5 GPa, crack resistance is 4.4±0.4 MPa·m1/2, compressive strength is 1.37±0.23 GPa, Poisson's ratio is 0.26±0.01, Young's modulus - 278±6 GPa, shear modulus - 110±2 GPa.