WU Chunrong, ZHANG Xiaozhen, ZHOU Jianer, JIANG Yuhua, LI Yueming

(School of Materials Science and Engineering, Jingdezhen Ceramic Institute, Jingdezhen 333001, Jiangxi, China)

Abstract: Ta₂O₅-La₂O₃ system ceramic materials were prepared by dry pressing and high temperature solid-state reaction sintering techniques. The infl uences of La₂O₃ content on the phase composition, microstructure, thermal expansion coeffi cient (TEC) and bending strength of prepared ceramic samples were investigated. Results show that the pure Ta₂O₅ ceramic, composed of orthorhombic phase Ta₂O₅ , shows obvious microcracking phenomena and exhibits low bending strength and low negative thermal expansion coeffi cient. Orthorhombic phase LaTa₇O₁₉ acicular crystals as minor phase were formed with the addition of 5% La₂O₃ . The amount of LaTa₇O₁₉ crystalline phase increases with the increment of La₂O₃ content, and the sample with 12.5% La₂O₃ is mainly composed of LaTa₇O₁₉ crystalline phase. The addition of small quantity of La₂O₃ could effectively inhibit the growth of Ta₂O₅ grains and avoid the generation of microcracks. Low positive TEC and increased bending strength could be obtained for Ta₂O₅-La₂O₃ system ceramic with 3% and 5% La₂O₃ . The sample with 5% La₂O₃ shows a TEC of 3.4×10-6 ℃-1 and bending strength of 81.4 MPa sintered at 1400 ℃for 2 h.

Key words: low expansion ceramic; tantalum pentoxide; lanthanum oxide; thermal expansion coeffi cient; bending strength