Mikrostruktura transparentní keramiky YAG (yttrium-aluminium granát) byla charakterizována pomocí r?zných deskriptor? se zam??ením na velikostní ?ísla zrn. Jak lineární, tak planární velikostní ?ísla zrn byla pou?ita k popisu závislosti pr?m?rné velikosti zrn na koncentraci ytterbitého (Yb) dopantu (0-10 at.%), koncentraci slinovací p?ísady - tetraethylorthosilikát, TEOS (0,3-0,5 hm.%) a dob? slinování. P?esto?e ob? tato velikostní ?ísla zrn mají podobné hodnoty u studovaných materiál? (jejich pom?r je tém?? jednotkový, 0,987 ± 0,109), jsou principiáln? nezávislá a poskytují vzájemn? se dopl?ující informace o mikrostruktu?e. Rovn?? jejich vztah k dal?ím mikrostrukturním deskriptor?m (hustota rozhraní, hustota integrálu st?edního zak?ivení, st?ední délka úsek?, Jeffriesova velikost) je diskutován. Bylo zji?t?no, ?e obsah Yb v?t?í ne? 3 at.% potla?uje p?i del?í dob? slinování r?st velikosti zrn. Rozdíly v koncentraci TEOSu v rozmezí 0,3-0,5 hm.% nemají ?ádný prokazatelný vliv na velikost zrn. Nejvýrazn?j?í vliv na mikrostrukturu má r?zná doba slinování, kdy prodlou?ená doba slinování pochopiteln? vede k r?stu zrn, nicmén? se zvy?ujícím se obsahem Yb není tento r?st tak výrazný: pro YAG vzorky bez dopování Yb vede osminásobné zvý?ení doby slinování (ze 2 h na 16 h) k poklesu velikostních ?ísel zrn o 33,2-35,0%, kde?to s obsahem Yb 10 at.% je odpovídající sní?ení velikostních ?ísel pouze 8,7-10,0%. Tato zji?t?ní odpovídají výsledk?m získaných pomocí jiných mikrostrukturních deskriptor?.
The microstructure of transparent yttrium-aluminum garnet (YAG) ceramics is characterized using different microstructural descriptors, with special focus on grain size numbers. Both linear and planar grain size numbers are used to describe the dependence of the average grain size on Yb dopant content (0-10 at.%), sintering additive (tetraethyl orthosilicate, TEOS) content (0.3-0.5 wt.%) and firing time. Although the two grain size numbers are very close for the materials studied (with ratios very close to unity, around 0.987 ± 0.109), these two numbers are principally independent and provide complementary microstructural information. Their relations to other microstructural descriptors (interface density, mean curvature integral density, mean chord length, Jeffries size) are discussed throughout the text. It is found that Yb doping of more than 3 at.% has a grain-growth-inhibiting effect (after sufficiently long firing times), but differences in the TEOS content between 0.3 and 0.5 wt.% do not have any sensible effect. The largest effect on the microstructure is exerted by the firing time (with prolonged firing times leading to grain growth), but with higher Yb doping the effect of firing time on the grain size becomes less pronounced: for YAG samples without Yb doping, increasing the firing time by a factor of 8 (from 2 h to 16 h), deceases the grain size number by 33.2-35.0 %, whereas with a Yb dopant content of 10 at.%, the corresponding decrease in the grain size number is only 8.7-10.0 %. These findings are fully corroborated using the other microstructural descriptors.
Charakterizace mikrostruktury transparentní YAG keramiky pomocí mikroskopické obrazové analýzy se zvlá?tním ohledem na velikostní ?ísla zrn.
L Esposito
2014
Abstract
The microstructure of transparent yttrium-aluminum garnet (YAG) ceramics is characterized using different microstructural descriptors, with special focus on grain size numbers. Both linear and planar grain size numbers are used to describe the dependence of the average grain size on Yb dopant content (0-10 at.%), sintering additive (tetraethyl orthosilicate, TEOS) content (0.3-0.5 wt.%) and firing time. Although the two grain size numbers are very close for the materials studied (with ratios very close to unity, around 0.987 ± 0.109), these two numbers are principally independent and provide complementary microstructural information. Their relations to other microstructural descriptors (interface density, mean curvature integral density, mean chord length, Jeffries size) are discussed throughout the text. It is found that Yb doping of more than 3 at.% has a grain-growth-inhibiting effect (after sufficiently long firing times), but differences in the TEOS content between 0.3 and 0.5 wt.% do not have any sensible effect. The largest effect on the microstructure is exerted by the firing time (with prolonged firing times leading to grain growth), but with higher Yb doping the effect of firing time on the grain size becomes less pronounced: for YAG samples without Yb doping, increasing the firing time by a factor of 8 (from 2 h to 16 h), deceases the grain size number by 33.2-35.0 %, whereas with a Yb dopant content of 10 at.%, the corresponding decrease in the grain size number is only 8.7-10.0 %. These findings are fully corroborated using the other microstructural descriptors.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
