Pre-perovskite nanofiber: a new direct-band gap semiconductor with green and near infrared photoluminescence

Abstract

Perovskite-related oxides exhibiting fascinating electric and magnetic properties are important functional materials. We report, for the first time, that pre-perovskite (PP) PbTiO 3 , characterized by one-dimensional (1D) TiO 6 octahedron columns, has a direct-band structure with a gap of 3.20 eV. The faceted single-crystal nanofibers of PP-PbTiO 3 demonstrate strong green and near infrared (NIR) photoluminescence (PL) emission at room temperature, which are intrinsic and subjected to quasi-1D crystal structure and electronic band structure. These nanofibers serving as new direct band-gap semiconductors may find applications in novel optical and optoelectronic devices. Experimental section Preparation and characterizationThe nanofibers of pre-perovskite PbTiO 3 were prepared by a polymer-assisted hydrothermal method. Chemistry grade

Photocatalytic Degradation of Congo Red Using PbTiO3 Nanorods Synthesized via a Sonochemical Approach

“…Peaks at 102, 163, 247, 291, 412, 461, 565, and 611 cm −1 were assigned to the major typical Raman bands of PbTiO 3 and these Raman‐active modes with the symmetries of A1(1TO), E(2TO), B1+E, A1(2TO), E(2LO)+A1(2LO), E(3TO), A1(3TO), E(3LO), and A1(3LO) which corresponds with the tetragonal phase of PbTiO 3. ,…”

A study of structural phase transition, vibration, optical, and magnetic properties of Fe-doped PbTiO3 nanostructured powders

“…5a). The optical band gap of all samples was estimated from the tangent lines of Tauc's plot, exhibiting a decreasing trend from 2.75 eV for pure PTO sample [18,19] to 2.07 and 1.69 eV for Fe10 samples calcined at 500 and 900°C, respectively (Fig. 5b).…”

Pressure on the Structure and Thermal Properties of PbTiO3: First-principle Study

“…使用 BFGS 最小算法对 PTO 三种晶体进行弛 豫，计算的晶格常数和形成焓如表 1 所示。可以看 出压力为 0 的情况下(0 GPa)晶格常数与前人计算 结果 [10,[18][19] 以及实验值 [8,20] 相比十分接近，TP-PTO、 CP-PTO 形成焓与 Alahmed [21] 和 Niu [22] 等的结算结 果十分接近，这证明本研究的计算参数和方法是可 行的。形成焓是物质反应后释放或吸收的能量，是 衡量相结构稳定性的重要指标。 当形成焓为负值时， 其绝对值越大，表示此化合物越易形成 [23] 。计算结 果表明 TP-PTO、CP-PTO、PP-PTO 结构是稳定的， 稳 定 性 由 大 到 小 依 次 为 ： [9][10]25,[29][30][31] 。可以看出，本计算结果与实验值相比明 显偏小，这是由于密度泛函理论未考虑电子与电子 之间的交换关联势的不连续性，使多粒子体系中激 发态电子间关联作用被低估 [24] 。 TP-PTO 和 CP-PTO 计算结果与 Zhang [19] 和 Hosseini [25] 等的结果十分吻 合， 而 PP-PTO 的计算值比 Zhou 等 [10]…”

“…b : Values from calculation and experiment in other literatures are 1.70 [25] and 3.40 [30] eV, respectively. c : Values from calculation and experiment in other literatures are 1.96 [10] and 3.20 [31] eV, respectively 重轴(4/m)的镜像对称的四方结构，所以有 7 个独立 弹性常数 [9] ，即 C11、C33、C44、C66、C12、C13、C16。 表 3 列出了压力为 0 的情况下 TP-PTO、CP-PTO、 PP-PTO 弹性常数(Cij) [9,18,[34][35] 。TP-PTO 和 CP-PTO 与 Long 等 [18] 的计算结果十分接近，进一步证明了 本次计算结果的准确性。PP-PTO 的弹性常数与 Liu 等 [9] 的计算结果有一定偏差，原因在于本研究所使 用的势函数和赝势与其不同。PTO 的弹性常数随压 力的变化趋势如图 4 所示。为进一步研究 TP-PTO、 CP-PTO、PP-PTO 在 0~30 GPa 压力下的力学稳定 性，本研究通过力学稳定性判据判断其稳定性： 立方晶系 [32] C11-C12>0， C11>0， C44>0， C11+2C12>0 (1) 四方晶系 [33] C11>0，C33>0，C44>0，C66>0 Expt. [34] 237 60 69 144 90 70…”