|
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·m1/2 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.
|