Study On Microstructure And Properties Of Al₂O₃ Ceramics Toughened With LiTaO₃ Of Different Grain Sizes

For toughening Al₂O₃ ceramics,the paper introduced LiTaO₃ powders of different grain sizes into Al₂O₃ structural ceramics as the second phase,investigate the influence of the LiTaO₃ grain size on the microstructure and mechanical properties of LiTaO₃/Al₂O₃ composite ceramics(the LTA),explore formation mechanism of domain structures in the LiTaO₃ grain also,research work has important scientific significance for development of ceramic materials structure design and Toughening technology.Research shows LiTaO₃ powders with 91nm,125nm,310nm,324nm,386nm grain sizes are synthesized by sol-gel precursor calcined at 650℃,750℃,800℃,850℃, 900℃for 2h,the precursor prepared,using Ta₂O₅ and Li₂CO₃ as raw materials,citric acid(CA) as chelating agent,ethylene glycol(EG)as esterification agent and polyethylene glycol(PEG) as dispersant agent by the sol-gel technique.Al₂O₃ ceramics with LiTaO₃ of different grain sizes prepared at 1350℃for 90min by hot-pressed sintering,the relative density is above 96%.Study shows that with decrease initial grain size of LiTaO₃,the flexural strength and fracture strength increased, when 15vol%LiTaO₃ powders of 91nm introduced Al₂O₃ ceramics,the LTA composite ceramics' flexural strength and fracture strength values reached 511MPa and 6.13MPa·m^1/2 respectively.When LiTaO₃ grain size is about 100nm decreasing trend of the mechanical properties is Obvious,showing typical "threshold effect of second phase particle size".Research found the domain structure Characteristics are "wedge-shaped","banded", "Lamellar" 90°domain in the LiTaO₃ grains of LTA composite ceramics,clarify the formation mechanism 90°ferroelectric domain is the "stress-induced mechanism".The study reveals the second phase of LiTaO₃ toughening mechanisms are "crack deflection" and "energy consumption toughening of domain switching" synergy mechanism in LiTaO₃/Al₂O₃ composite ceramics.