Talc ceramics, also known as block talc ceramics or talc ceramics, are a type of high-frequency device ceramics with excellent electrical properties. Talc porcelain low dielectric constant (generally e=6-7); Low tangent value of dielectric loss angle tanδ Fluctuating between (3-20) ×10-4, insulation strength is usually 20-30kV/mm, and volume resistivity is high (volume resistivity at 100 ℃ is about up to 1014Ω· cm), the static bending strength is usually 120-200MPa, and the chemical stability is good, acid resistant, alkali and corrosion resistant. From the perspective of frequency characteristics, the dielectric constant of talc ceramics decreases with increasing frequency, and changes little with increasing temperature at high frequencies. Tanδ At f=106Hz used to decrease with the increase of frequency, so it fully demonstrates the advantages of talc ceramics when used as high-frequency device ceramics. Due to the high insulation strength, low dielectric loss, and excellent high-frequency characteristics of talc ceramics, although the dielectric constant is not high enough, it can still be used as a high-voltage high-power ceramic capacitor. The low loss talc ceramic used as a high-power ceramic capacitor has a dielectric loss angle tangent value that can reach (3.5-4) × 10-4.
talc ceramics also have a deficiency that must be given sufficient attention: if production control is improper, talc porcelain will not be placed properly. Or aging phenomenon may occur during use, which is caused by the crystal transformation of the main crystalline phase magnesium metasilicate, resulting in ceramic powder formation, cracking, strength reduction, and deterioration of dielectric properties; The sintering range is narrow, usually only around 20 ℃. If the sintering control is not good, it often causes deformation, blistering, bonding of padding, and generates waste products. Practice has shown that in the production of talc ceramics, if the raw materials, formula, or production process are not properly controlled, aging often occurs. Once it occurs, it will bring serious harm and loss to production and use, and aging phenomenon must be highly valued. Research has confirmed that the aging or pulverization of talc ceramics is due to the crystal transformation of magnesium metasilicate (MgSiO3), the main crystalline phase of talc ceramics, as well as the effects of strain and stress during the crystal transformation process.