Processing And Study On B₂O₃–Nb₂O₅–SrO-BaO Glass Ceramics

Due to good performance of ferroelectric glass ceramics which own both advantages of glass and ferroelectrics, glass ceramic materials are attracting more and more material scientist's attention. Specially, as the high energy density capacitance, the ferroelectric glass ceramics own huge application value. In ferroelectric glass ceramics, since glass ceramic with high permittivity and high breakdown voltage can meet requirement of power electronics and pulsed power application, a large number of investigations have been started all over the world. In this degree thesis, a series of B₂O₃– Nb₂O₅– SrO– BaO glass ceramics were prepared and studied.Transparent 58B₂O₃- 10Nb₂O₅- 10Li₂O and 58B₂O₃– 10Nb₂O₅– 10SrO– 10BaO glass matrixes were prepared by conventional melting. The effect of heating mechanism was both studied in these two glass ceramics. The result proved that high heating temperature and long heating time were helpful to improve these glass ceramics'crystallization and dielectric performance. The 58B₂O₃- 10Nb₂O₅- 10Li₂O glass ceramics heated at 650℃for 4 h gained a relative dielectric constant of 25 and a breakdown strength of 18.5KV/mm. The 58B₂O₃– 10Nb₂O₅– 10SrO– 10BaO glass ceramic heated at 800℃for 4h gained a relative dielectric of 65 and a breakdown strength of 20.1KV/mm. In addition, in order to a33- 10Nb₂O₅- 10Li₂O abided by bulk crystallization and 58B₂O₃– 10Nb₂O₅– 10SrO– 10BaO glass ceramic was surface crystallization.58B₂O₃- 10Nb₂O₅- 10Li₂O abided by bulk crystallization and 58B₂O₃– 10Nb₂O₅– 10SrO– 10BaO glass ceramic was surface crystallization.58B₂O₃– 10Nb₂O₅– 10SrO– 10BaO glass ceramics with addition of BST, PLZST, and BaF₂ were prepared. The result showed that BaF₂ could improve the glass ceramics'dielectric constant. And the dielectric breakdown performance was not affected. Then the contents of Nb₂O₅, SrO and BaO were modified in glass ceramics with BaF₂ and the change of these contents was obvious. 58B₂O₃– 11Nb₂O₅– 11SrO– 11BaO- 3BaF₂ glass ceramic's relative dielectric constant was the highest:εr=116, tanθ=0.011, Ev=25KV/mm, We =0.32J/cm3。.A series of strontium barium niobate-based B₂O₃ system glass ceramics have been prepared by conventional melting and heat-treated crystallization method. The effect of BaF₂ addition innucleation and crystallization kinetics has been explored for dielectric applications. BaF₂ addition decreased the activation energy of crystallization obviously and changed microstructure of glass–ceramics significantly. The dielectric constant and breakdown strength of glass–ceramics were improved significantly by adding BaF₂. The glass–ceramic with a relative dielectric constant of 337, a breakdown strength of 52.7 kV/mm and an energy density of 4.14J/cm3 was achieved.