Application of magnesium oxide in ceramics

Magnesium oxide (MgO) is a white fine ceramic powder, which can be sintered by itself to make MgO ceramics, but also synthesized, compounded or used as additives with other compounds to make high performance ceramics or crystals. typical application scenarios of MgO are as follows.

I. Typical applications as the main component

1. MgO transparent ceramics

MgO transparent ceramics have the advantages of low density, high temperature resistance, high insulation, excellent mechanical properties, high infrared transmittance, good chemical stability and low emissivity, etc. They are a high-performance infrared window and sensor protection material, etc.

2. MgAl2O4 transparent ceramics

MgAl2O4 transparent ceramics have excellent optical transmittance covering almost the UV to IR region (190nm＜λ＜6000nm), and also have the advantages of high hardness, high strength, high temperature resistance, low emissivity, sand and rain corrosion resistance and impact resistance, etc. They have been widely used in transparent armor, missile windows and fairings, etc. MgAl2O4 is made of MgO and Al2O3 according to the stoichiometric ratio MgAl2O4 is produced by the reaction of MgO and Al2O3 in the stoichiometric ratio of 1:1, and the mass proportion of MgO is 28.2%.

3. Co2+ doped MgAl2O4 crystals

Co2+-doped magnesium-aluminum spinel (Co:MgAl2O4) crystal is an effective material for passive Q-modulated solid-state lasers operating in the near-infrared region, and the high peak power pulsed laser generated by its passive Q-modulation has the characteristics of small damage to human eyes, strong penetration ability, low transmission loss and strong photoelectric countermeasure, which can be widely used in space optical communication, rapid range measurement on the battlefield and unmanned equipment for The 99.995% mass ratio of high-purity MgO in Co2+-doped MgAl2O4 crystals is similar to that of MgAl2O4 transparent ceramics.

4. MgO-Y2O3 complex-phase ceramics

By using the \”pegging effect\” between MgO and nano-Y2O3 to mutually inhibit grain growth, MgO-Y2O3 complex-phase ceramics with higher mechanical properties and optical transmittance than single-phase can be prepared, which can be used to manufacture transparent armor, missile hoods, high-temperature observation windows and aerospace windows. The volume ratio of MgO to Y2O3 in MgO-Y2O3 complex-phase ceramics is usually 1:1, which translates into a mass MgO ratio of about 41.7%.

5. MgO-based microwave dielectric ceramics

With the new iteration of mobile communication, satellite communication technology, people\’s requirements for communication time frequency band is getting higher and higher, making low dielectric high Q ceramics become a research hot spot. On the one hand, MgO ceramics have superior dielectric properties (εr=9.1,tanδ＜1.6×10-6), which is an ideal substrate material for microwave dielectric for 5G communication. On the other hand, MgO-TiO2 series (mainly MgTiO3) microwave dielectric ceramics have important application prospects in electronic components such as resonators and filters due to their excellent dielectric properties. MgTiO3 is produced by the 1:1 stoichiometric reaction of MgO and TiO2, with MgO mass ratio of 33.3%.

II. Typical applications as additives

1. as a sintering additive for high performance ceramic heat dissipation substrate

With the development of high-power electronic devices in the fields of high-speed rail, aerospace and military industry towards high temperature, high frequency and high integration, etc., efficient heat dissipation becomes an urgent demand. High-power devices realize heat exchange with the outside world through ceramic copper-clad plates. Currently, the mainstream ceramic substrates are Si3N4, AlN and Al2O3, all of which require MgO as a sintering aid. Especially for Si3N4 ceramics with excellent overall performance, MgO becomes the sintering aid of choice for the preparation of high thermal conductivity Si3N4 ceramics with a usage of about 3% in order to avoid the lattice defects generated by Al2O3 as an aid to increase phonon scattering.

2. As a sintering aid for transparent ceramics such as Al2O3, YAG and AlON

MgO as an additive can significantly reduce the solid-phase reaction temperature, drag the rate of grain boundary migration, discharge pores and promote densification; inhibit grain boundary migration through the pegging effect, avoid abnormal grain growth and optimize mechanical properties. The amount of MgO added to such transparent ceramics is relatively low (<1%), but its dispersion is very important.

3. As a sintering aid for ZTA wear-resistant ceramics

Both Al2O3 and ZrO2 have properties such as high temperature resistance, wear resistance and better biocompatibility. The preparation of ZTA nanocomposite ceramics by toughening Al2O3 with ZrO2 can enhance their strengths and avoid their weaknesses, and give full play to their integrated advantages, which have important applications in aerospace, engine wear-resistant parts and artificial femoral ball heads, etc. The densification and grain refinement mechanism of MgO in ZTA ceramics is similar to that in Al2O3, and its usage is about 2%.

4. As LiNbO3 crystal additive

Magnesium-doped lithium niobate (MgO:LiNbO3) crystals, which have their unique advantages in the application of NCPM multiplication, mixing and optical parametric oscillation (OPO) in lasers, are widely used in optical parametric oscillation, optical parametric amplification (OPA), quasi-phase matching and integrated optical waveguides. The Curie temperature of LiNbO3 can be regulated using 99.995% high purity MgO doping, which is typically less than 5 mol%, converting to about less than 1.4% by mass.

The acquisition of high performance ceramics is closely related to the performance of its starting materials as well as additives. The high purity ultra-fine and highly dispersed magnesium oxide produced by applying unique purification process and granulation technology has the following advantages.

(1) High purity of 99.95% and 99.995% with very low sodium content.

(2) Good dispersion, easy to achieve uniform distribution in various ceramic substrates.

(3) Small particle size, uniform size distribution, high sintering activity; good sphericity, good fluidity, easy to shape.

Once the highly dispersible magnesium oxide is introduced, it has caused a warm response in the market of thermal conductivity ceramics, transparent ceramics and functional ceramics. The research institutes, universities and related benchmark enterprises who have used this product unanimously agree that the various products prepared by using highly dispersible magnesium oxide meet or exceed the expectation in terms of product performance and stability.