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Influence of Chemical Composition and Y 2 O 3 on Sinterability, Dielectric Constant, and CTE of β‐SiAlON
Author(s) -
Ganesh Ibram,
Thiyagarajan Natarajan,
Jana Dulal Chandra,
Mahajan Yashwant Ramachandra,
Sundararajan Govindan
Publication year - 2008
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2007.02144.x
Subject(s) - materials science , sintering , sialon , fracture toughness , dielectric , microstructure , composite material , flexural strength , thermal expansion , ceramic , analytical chemistry (journal) , mineralogy , chemistry , optoelectronics , chromatography
Different types of dense β‐Si 6− z Al z O z N 8− z ( z =1, 1.5, 2, 2.5, 3, 3.5, and 4) ceramics have been prepared following a conventional reaction sintering process at 1675°–1700°C using α‐Si 3 N 4 , α‐Al 2 O 3 , AlN, and 3–7‐wt% Y 2 O 3 as raw materials. Sintered materials were thoroughly characterized for bulk density (BD), apparent porosity (AP), water absorption (WA) capacity, phase formation, microstructure, coefficient of thermal expansion (CTE), hardness, fracture toughness, three‐point bent strength, and dielectric constant at 16–18 GHz frequency. Characterization results suggest that an increase in z value, Y 2 O 3 concentration, and sintering temperature leads to an increase in β‐SiAlON phase formation, BD, grain size, fracture toughness, and dielectric constant, and as a consequence, AP, WA capacity, hardness, and three‐point bend strength of the materials decrease. These materials also exhibited stable and low dielectric constants (5.67–7.67) between 16 and 18 GHz frequency. The β‐Si 4 Al 2 O 2 N 6 exhibited a BD of ∼3.06 g/mL, AP of ∼0.01%, WA capacity of ∼0.01%, ∼94.43%β‐SiAlON phase, a hardness of ∼1317 kg/mm 2 , a fracture toughness of ∼3.30 MPa·m 1/2 , a three‐point bend strength of ∼226 MPa, a CTE of 3.628 × 10 −6 °C −1 between 30° and 700°C, and a dielectric constant of ∼7.206 at 17 GHz after sintering at 1675°C for 4 h with 7‐wt% Y 2 O 3 .