Dy固溶βーCa_3(PO_4)_2マシナブルセラミックスの作製と二・三の物性

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The mixed powders of β-Ca_3(PO_4)_2 (TCP) and DyPO_4 with mole ratios (Dy/TCP) 0〜1.0 were uniaxially dry-pressed at 50 MPa to disks or bars, before cold isostatic pressing at 100 MPa. The specimens were fired at 1000〜1400℃ for 10 min-20 hrs in air. The phases observed in the fired specimens above 1250℃ were α-TCP and HAp for Dy/TCP mole ratio=0〜0.01, α-TCP, Dy-containing β-TCP and HAp for Dy/TCP ratio=0.05, Dy-containing β-TCP and HAp for Dy/TCP ratio=0.10〜0.35, and Dy-containing β-TCP, DyPO_4 and HAp for Dy/TCP ratio=0.40〜1.0. The upper solubility limit of Dy in β-TCP was reached when the Dy/TCP ratio was 0.33. The relative density≩95% was achieved when the Dy/TCP ratio was 0.10〜0.25 above 1300℃ (3 hrs). The maximum relative density was 97% at 1300℃, over 98% at 1350〜1400℃ when the Dy/TCP ratio was 0.18. The sintered specimens (relative density ≩95%) could be machined using metallic gravers or dental burs. The reason why the Dy-containing β-TCP ceramics are machinable seems to be due to the easy transgranular fracture of β-TCP grains doped with Dy. The three-point bending strength and Vickers'hardness of the bars sintered at 1300℃ for 3 hrs were in the range 30〜50 MPa and 2〜3 GPa, respectively, when the Dy/TCP ratio was 0.10〜0.25. However, increasing firing temperature over 1350℃ tended to decrease the bending strength because of grain growth. The linear thermal expansion coefficients were within 11〜12×10^<-6>/℃(-900℃). The citric solubility%, which was determined under the condition of 1 g of Dy-containing β-TCP powder (fired at 1300℃ for 3 hrs) and 150 ml of 2% citric acid solution at 20℃ for 1 h, was about 95% when the Dy/TCP ratio was 0.05〜0.33.
社団法人日本材料学会の論文
1995-07-15

Dy固溶βーCa_3(PO_4)_2マシナブルセラミックスの作製と二・三の物性

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