As an additive, MgO influences the mechanical characteristics and microstructure of a variety of ceramics and plays a crucial role in the manufacturing of advanced ceramics.
Effects of Magnesium Oxide Additive on Alumina Ceramics
Effects of MgO on Sintering Temperature and Densification
Magnesium oxide, a typical sintering aid, can successfully lower the sintering temperature of alumina ceramics. Alumina ceramics were created using spark plasma sintering technology using high-purity a-Al2O3 powder as the raw material and MgO as a sintering aid. The findings demonstrate that adding the right amount of MgO can increase density, reduce grain growth, and lower the sintering temperature of alumina ceramics. The ideal addition of MgO is at a mass fraction of 0.25%.
Effects of MgO on Mechanical Properties and Grain Growth
A two-step sintering process using alumina powder as the raw material and MgO as an additive was used to create alumina ceramics. The findings demonstrate that the relative density, flexural strength, and hardness of alumina ceramic sintered samples first rise and then slightly decrease with the increase of MgO content. Mg accelerates the grain boundary diffusion, has some impact on grain refinement, and improves density and mechanical properties when the MgO content is less than the solid solution limit. However, when the MgO content exceeds the solid solution limit, grain refinement is still affected. The result is enhanced, but the magnesium aluminum spinel that forms at the grain boundary prevents pores from discharging.
In terms of grain growth, the samples' grain size and uniformity initially increased and then slightly decreased with the addition of more MgO. When the MgO content is 0.5%, the grains are finer, the grain distribution is more uniform, and the largest grain size is only 2.2 um, but the densification is the worst. When the MgO content is 0.25%, the average particle size is the smallest, the grain distribution is concentrated, and the performance is best.
Effects of MgO on Optical Properties
MgO has similar effects on the mechanical characteristics and compactness of transparent alumina ceramics as it does on ordinary alumina ceramics. Its mechanical qualities, compactness, and grain growth inhibition are all improved by the appropriate addition of MgO. When the MgO doping level is low, transparent alumina ceramics have relatively high light transmittance because they are denser and have higher transmittance in terms of optical properties.
However, as the amount of doping increases, the second phase will form locally, creating a light scattering center and lowering the transmittance of transparent ceramics once the MgO content exceeds the solid solubility in Al2O3.
Effects of Magnesium Oxide Additive on ZnO Linear Ceramics
Large resistivity range, high flow density, low nonlinear coefficient, and low temperature coefficient of resistance are just some of the benefits of using ZnO linear ceramic resistors in industrial production. They are extensively utilized in household appliances, communications, transportation, and power electronics. Traditional ZnO composite ceramics still have a lot of issues, including poor structural uniformity, a low rate of industrial production repetition, and weak stability.
The temperature resistance coefficient of ZnO ceramic resistors is improved by the addition of MgO. The density of ceramics can be increased with the proper amount of MgO, but too much will cause the density to decrease.
Effects of Magnesium Oxide Additive on Ferroelectric Ceramics
Effects of MgO on Barium Strontium Titanate Ceramics
Because of its high tunability and low dielectric loss, barium strontium titanate (BST) ferroelectric ceramic material has a promising application as a phase shifter in a phased array and a tunable device at microwave frequencies. For barium strontium titanate materials to be used on a large scale, it is necessary to solve the problem of improving the comprehensive performance of current ferroelectric materials by means of a variety of methods.
Aside from A-site doping substitution with rare earth element ions, adding MgO, MgTiO3, Mg2SiO4, and other compounds to BST ceramics and films can reduce their dielectric constant and dielectric loss.
Effects of MgO on BaTiO3-Based Ceramics
BaTiO3-based ceramic powder is uniformly coated with MgO using the uniform precipitation method to create MgO-coated BaTiO3-based ceramic composite particles. The findings demonstrate that the coating agent MgO can successfully prevent grain growth in order to produce ceramics with uniform grains. The fine-grain effect is caused by MgO inhibition at the grain boundary, and MgO aids in the formation of "shell-core" structure grains, increasing resistivity and breakdown voltage strength.
Effects of Magnesium Oxide Additive on YAG Transparent Ceramics
High melting point (1950°C), high strength, high thermal conductivity, and stable physical and chemical properties are all characteristics of YAG transparent ceramics. They have demonstrated excellent potential for use as both structural and functional materials.
Vacuum solid-state reaction sintering technology can be used to create high-quality YAG transparent ceramics, and MgO can be used as a sintering aid. MgO is useful for regulating the growth of grains, the elimination of pores, and the diffusion of grain boundaries. However, excessive MgO content will form a second phase in the ceramic or cause it to sinter and shrink too quickly, forming pores that cannot discharge the crystal grains and greatly reducing the transmittance of the YAG ceramic.
Effects of Magnesium Oxide Additive on Sialon Ceramics
Sialon is a Si3N4-based solid material. Because the diffusion coefficient of Si3N4 is very low, when Sialon is synthesized, it is usually accompanied by a decomposition reaction when it reaches the sintering temperature of Sialon ceramics (greater than 1800 ° C). Low-temperature sintering is therefore essential for the preparation of Sialon ceramics.
MgO can increase the density of β-sialon ceramics and reduce the sintering temperature. Flexural strength and fracture toughness of β-sialon ceramics increase initially and then decrease as the sintering temperature rises. The prepared β-sialon ceramic materials are tightly bonded when the sintering temperature reaches 1600°C, and the flexural strength and fracture toughness are at their highest.