ABSTRACT

We report the effect of various Bi:Ti ratios x:1 (x = 0.5–3) on the phase formation of sodium-bismuth titanate Na_0.5Bi_0.5TiO₃ (NBT) during hydrothermal synthesis (230°С, 3 MPa, 96 h) from titanium oxide and bismuth hydroxide in 20 M NaOH solution. It was shown that single-phase ceramics with perovskite structure could be obtained at x = 0.5–0.9 using the hot-pressing technique (1025°С, 60 MPa, 1 h). At x = 1, hydrothermal synthesis results in single-phase samples, while, after sintering, the admixture of Na₂Ti₃O₇ was detected. At x = 2 and 3, samples contained admixtures after hydrothermal synthesis. The x–value does not significantly affect the composition of perovskite-like products despite the excess of bismuth in the system. The chemical composition of the samples with x = 0.5–0.9 corresponds to the general formula Na_0.60–0.69Bi_0.40–0.31TiO_2.9–2.81δ_0.10–0.19 (where δ represents vacancies in oxygen sublattice). The Bi³⁺ content in the samples is underestimated due to the solubility of its hydroxide in a 20 M alkali solution. The properties of ceramics are not significantly affected by x values, and materials exhibit following average characteristics: electrical resistivity 1.3 × 10⁹ Ohm∙cm, tanδ = 0.15, К_р = 0.1, d₃₁ = 6.7 and d₃₃ = 9.5 pC/N, g₃₁ = 2.34 and g₃₃ = 3 mV∙m/N.

摘要

我们报告了水热合成（230°С，3 MPa，96）中各种Bi：Ti比x：1（x = 0.5-3）对钛酸铋钠Na _0.5 Bi _0.5 TiO ₃（NBT）相形成的影响。h）由氧化钛和氢氧化铋在20 M NaOH溶液中制得。结果表明，使用热压技术（1025°С，60 MPa，1 h）可以在x = 0.5-0.9时获得具有钙钛矿结构的单相陶瓷。在x = 1时，水热合成产生单相样品，而在烧结后，Na ₂ Ti ₃ O ₇的混合物被检测到。在x = 2和3时，水热合成后样品中含有混合物。尽管系统中铋过多，但x值不会显着影响钙钛矿状产品的成分。样品的化学组成，其中x = 0.5-0.9对应于通式的Na _0.60-0.69毕_0.40-0.31的TiO _2.9-2.81 δ _0.10-0.19（其中，δ表示氧亚晶格空位）。由于其氢氧化物在20 M碱溶液中的溶解度，样品中的Bi ³⁺含量被低估了。陶瓷的特性不受x值的显着影响，并且材料表现出以下平均特性：电阻率1.3×10 ⁹欧姆·厘米，tanδ= 0.15，_Кр  = 0.1，d ₃₁  = 6.7和d ₃₃  = 9.5 pC / N，g ₃₁  = 2.34和g ₃₃  = 3 mV∙m / N。