【作者】 刘向春；

【导师】 田长生；

【作者基本信息】 西北工业大学 ， 材料学， 2005， 硕士

【摘要】 钛酸锌陶瓷具有优良的微波介电性能,而且不加入烧结助剂即可于1100℃烧结。但是六方相ZnTiO₃会在945℃以上分解为微波介电性能极差的立方相Zn₂TiO₄,这将严重恶化陶瓷的微波介电性能。而且,钛酸锌陶瓷的烧结及相结构转变对原料的选取、助烧剂的种类及加入量极为敏感。因此,研究原料活性对钛酸锌陶瓷烧结行为的影响,选取合适助烧剂实现陶瓷低温烧结,并同时保持其优良介电性能,很有意义。 本文采用化学法结合传统的氧化物固相烧结技术合成钛酸锌（ZnTiO₃）,掺杂氧化物作为烧结助剂降低钛酸锌陶瓷的烧结温度,研究了原料活性和掺杂氧化物对钛酸锌陶瓷的低温烧结行为、微结构以及介电性能的影响。 选取醋酸锌、碱式碳酸锌,分别与纳米TiO₂和普通TiO₂,通过化学法结合传统氧化物固相烧结技术合成钛酸锌。实验发现,钛酸锌低温烧结对TiO₂极为敏感,而ZnO对陶瓷烧结影响不显著。以纳米TiO₂为原料制备的陶瓷,其烧结温度比采用普通TiO₂的降低了70℃,而且烧结范围更宽。 在研究原料对烧结温度影响的基础上,我们选取碱式碳酸锌和纳米TiO₂为原料制备钛酸锌,分别单独掺杂V₂O₅和WO₃作为助烧剂进一步促进陶瓷烧结。结果表明:单独掺杂V₂O₅和WO₃有效降低了陶瓷烧结温度,900℃烧结的掺杂0.75wt%V₂O₅钛酸锌陶瓷密度可达理论密度的96.1%,930℃烧结的掺杂3.00wt%WO₃钛酸锌陶瓷的密度达理论密度的95.2%;V₂O₅的添加使六方相ZnTiO₃的分解温度从900℃降到了850℃以下,V₂O₅富积于陶瓷体的晶界处,在V₂O₅富积区附近产生了异常长大的晶粒。而在烧结温度<950℃时,当WO₃掺杂量≤1.00wt%,钛酸锌陶瓷主晶相为立方尖晶石相Zn₂TiO₄;掺杂量为3.00wt%,主晶相为六方相ZnTiO₃。掺杂V₂O₅陶瓷的介电常数ε_r随温度升高而增大,在950℃达到最大值40.8（0.75wt%掺杂量）。900℃烧结的掺杂0.75wt%V₂O₅钛酸锌陶瓷的Q×f=8873GHz,ε_r=21.3;900℃烧结的掺杂1.00wt%WO₃钛酸锌陶瓷,在10MHz的测试频率下,其介电常数ε_r=23.6,介电损耗tgδ=3.03×10^-3。可以看出,掺杂剂的加入严重影响了其介电性能; 为了进一步提高陶瓷介电性能,在V₂O₅和WO₃掺杂的基础上,再加入B₂O₃试图得到介电性能良好的低温烧结陶瓷。氧化物复合掺杂V₂O₅-B₂O₃和WO₃-B₂O₃有效降低了陶瓷烧结温度,900℃烧结的掺杂1.00wt%3V₂O₅-B₂O₃的钛酸锌陶瓷,其密度达理论密度的95.7%,930℃烧结的3WO₃-B₂O₃掺杂钛酸锌陶瓷密度为理论密度的94.1%;B₂O₃的加入有效抑制了单独掺杂V₂O₅时产生的晶粒异常生长,随B₂O₃加入量增加,晶粒变得均匀一致;930℃烧结的V₂O₅-B₂O₃掺杂陶瓷的介电常数ε_r=27.3,介电损耗tgδ=1.92×10^-3;B₂O₃的加入有效抑制了WO₃单独掺杂时所导致的相分解,在陶瓷烧成的冷却阶段产生了纳米线度的六方ZnTiO₃的低温相Zn₂Ti₃O₈,沉积于930℃烧结的3WO₃-B₂O₃掺杂试样的Zn₂TiO₄相中;930℃烧结的WO₃-B₂O₃掺杂陶瓷的介电常数ε_r=20.7,介电损耗tgδ=5.67×10^-3。更多还原

【Abstract】 Zinc titanates ceramics have low sintering temperature （1100℃） and promising properties, and they can be sintered at 1100℃ without sintering aids. But hexagonal zinc metatitanate （ZnTiO₃） decomposes to orthotitanate （Zn₂TiO₄） with relatively bad microwave dielectric properties at ⁹45℃. It is extremely sensitive to the kinds and adding amount of raw materials and sintering aids to zinc titanates ceramics sintering and phase transition. So, it is very meaningful to prepare zinc titanates ceramics with relatively low sintering temperature and promising dielectric properties.Zinc titanate ceramics were prepared by conventional mixed-oxide method combined with a chemical processing. Doping oxides were added as sintering aids to lower the sintering temperature of the ceramics. Effects of raw materials on the low-temperature sintering and doping additions on microstructure and dielectric properties of zinc titanate ceramics were investigated.By conventional mixed-oxide method combined with a chemical processing, zinc titanates ceramics were prepared using zinc hydroxide carbonate, zinc acetate, TiO₂ and nanometer TiO₂. It was extremely sensitive to TiO₂ to the low- temperature sintering zinc titanates ceramics, while the effects of ZnO on the low- temperature sintering were not sensitive. The sintering temperature of samples with nanometer TiO₂ as raw materials decreased for 70℃ compared to that of samples with TiO₂.Based on the investigation of the effects of raw materials on the low-temperature sintering, zinc hydroxide carbonate and nanometer TiO₂ were selected to prepare zinc titanate ceramics with V2O5 and WO3 additions. The results showed that the sintering temperature was lowed significantly by V₂O₅ and WO₃ additions. Zinc titanate ceramics with 0.75wt% V₂O₅ addition could be well sintered to approach 96.1% theoretical density at 900 ℃, and to approach 95.2% theoretical density at 930 ℃ with 3.00wt% V₂O₅ addition. Also the phase transition temperature from hexagonal ZnTiO₃ phase to cubic Zn₂TiO₄ was lowed by adding V₂O₅. It was noticed that V enriched in the boundary of the exaggerated grains, while not be detected in the inner of exaggerated grains or in the boundary of small grains. At sintering temperature <950℃, orthotitanate phase Zn₂TiO₄ in zinc titanate ceramics with ≤1.00wt% WO₃ additions became major phase, while zinc metatitanate ZnTiO₃ became major phase with ≤1.00wt% WO₃ additions. For zinc titanate ceramics with V₂O₅ additions, the dielectric constants ε_r increased with the sintering temperature increasing. The highest dielectric constant （it reached 40.8） obtained at 950℃ when the amount of V₂O₅ addition reached 0.75wt%. The Q×f values of 0.75wt% V₂O₅-doped zinc metatitanate-based ceramics reached 8873GHz at 900℃ sintering temperature, while the dielectric constant reached 21.3. For zinc titanate ceramics with 1.00wt% WO₃ additions at 900℃ sintering temperature, ε_r=23.6 and tgδ=3.03×10^-3 in 10MHz region. It could be concluded that dielectric properties were affected seriously by adding sintering aids.To obtain zinc titanate ceramics with good dielectric properties, B₂O₃ was addedon the base of V2O5 and WO3 additions. The sintering temperature of zinc titanate ceramics was lowed by multiplex oxides of V2O5-B2O3 and WO3-B2O3 added. The bulk density of zinc titanate ceramics with 1.00wt% 3V2O5-B2O3 multiplex oxides addition reached 95.7% theoretical density at 900 °C. For zinc titanate ceramics with 1.00wt% 3WO3-B2O3 multiplex oxides addition, the bulk density reached 94.1% theoretical density at 930°C. The exaggerated grain growth resulted from single oxide V2O5 addition was restrained because of B2O3 added. For zinc titanate ceramics with 1.00wt% V2O5-B2O3 additions at 930°C sintering temperature, ￡r=27.3 and tg<5= 1.92x10* in 10MHz region. In addition, the phase decomposition resulted from single oxide WO3 addition was restrained because of B2O3 added, and nano-size Zn2Ti3Og phase, a low temperature form of ZnTiC>3, precipitated in Zn2TiO4 ph更多还原