Sintering of cordierite in the presence of MoO3 and crystallization analysis

N Djordjevic,M Mitric,V.P Pavlovic,N Obradovic,D Kosanovic

doi:10.2298/sos1403307d

Abstract

Cordierite (MAS) is difficult to sinter because of the very narrow sintering temperature range (1300-1400?C). Because a low temperature process is desirable, it is necessary to find functional ads which can allow easier sintering process at lower temperature. The influence of MoO3 on the preparation process of cordierite ceramics was investigated. 2MgO-2Al2O3-5SiO2 was researched by sintering followed binary systems: MgO/MoO3, Al2O3/MoO3 and SiO2/MoO3 (all sintered at 850?C and 1100?C, sintering time 2h). Composition of these systems was 80 mass% of oxide and 20 mass% MoO3. The effects of sintering, the composition and morphology were followed by X-ray diffraction and SEM microscopy. It has been found that MoO3, beside liquid phase, forms intermediary unstable compounds with MgO and Al2O3, which is the significance information for further research. MAS ceramics were sintered with 20 mass% MoO3 at 1100?C, 1200?C and 1300?C, during 2h.

Highlights

Cordierite (2MgO-2Al2O3-5SiO2) is a technically important ceramic which is applied in a great variety of areas
The influence of MoO3 on the preparation process of cordierite ceramics was investigated. 2MgO-2Al2O3-5SiO2 was researched by sintering followed binary systems: MgO/MoO3, Al2O3/MoO3 and SiO2/MoO3
Starting oxides with MoO3 were sintered isothermally at 850 and 1100οC in an air atmosphere for 2 hours and a heating rate of 10oC/min. Those samples were denoted as AM1 for Al2O3+MoO3 sintered at 850oC 2h; AM2 for Al2O3+MoO3 sintered at 1100oC 2h; MM1 for MgO+MoO3 sintered at 850oC 2h; MM2 for MgO+MoO3 sintered at 1100oC 2h; SM1 for SiO2+MoO3 sintered at 850oC 2h; SM2 for SiO2+MoO3 sintered at 1100oC 2h

Summary

Introduction

Cordierite (2MgO-2Al2O3-5SiO2) is a technically important ceramic which is applied in a great variety of areas. Cordierite and cordierite based glass ceramics, well known because of their low dielectric constant, high resistivity, elevated thermal and chemical stability and very low thermal expansion coefficient, are promising materials for electronic applications. Ceramic bodies with high cordierite content have excellent thermal shock resistance. They have low dielectric constants (~5) and low thermal expansion coefficient (20·107/oC) [4]. These properties make them suitable for a wide range of high-temperature applications [5,6,7,8,9] and semiconductors [10,11]

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