Optimization of mechanical and dielectric properties by controlling densification and microstructure in silicon nitride ceramics prepared by hot pressing method

Subject Areas :

S. Salman  S. Afghahi ¹ (Associate Professor, Faculty of Engineering, Imam Hossein University, Tehran, Iran.)
Amirhossein  kouchaki foroshani ² (Ph.D. student Department of Ceramic, Materials and Energy Research Center, Karaj, Alborz, Iran)
Pouria  Dehghani ³ (Researcher Faculty of Engineering, Imam Hossein University, Tehran, Iran.)
farhood  heydari ⁴ (Ph.D. student, Researcher at Advanced Materials and Nanotechnology Research Center, Imam Hossein University, Tehran, Iran)

Received: 2022-09-09 Accepted : 2023-02-18 Published : 2023-11-22

Keywords: Mechanical Properties, Silicon Nitride, dielectric, Hot press.Sintering,

Abstract :

Silicon nitride ceramics are materials with excellent mechanical, dielectric and thermal properties which with such properties is one of the main candidates for use in high temperature environments. In this study, the effect of sintering temperature on microstructure control and densification and optimization of mechanical and dielectric properties of silicon nitride ceramics prepared by hot pressing at different temperatures of 1500 °C, 1600 °C, 1700 °C and 1800 °C has been investigated. Scanning electron microscopy and X-ray diffraction have been used to study the microstructure and analysis of the formed phases, respectively. According to the X-ray diffraction pattern and the Gazara-Mesier relationship, in the sintered samples at 1600 °C and 1700 °C, all alpha phases were converted to beta, and in the sintered samples at 1500 °C, the conversion rate was 95.45%. Is. The results show that increasing the sintering temperature from 1500˚C to 1800˚C leads to larger rod-shaped grains and achieves dual microstructure and the average grain diameter has increased from 0.7 µm to 1.34 µm. sintered specimen at 1500 °C, with the lowest average diameter (0.7 µm) among other specimens, has the highest flexural strength of 550 ± 9.5 Mpa. Is By increasing the average grain size and decreasing the α/β phase ratio due to the increase in fusion temperature, the mean dielectric constant and tangent of the sample loss increased from 4.5 to 9.2 and from 0.099 to 0.22, respectively