Preparation of Nb-Substituted Titanates by a Novel Sol−Gel Assisted Solid State Reaction

Abstract

Single-phase layered Nb-substituted titanates, Na(2)Ti(3-x)Nb(x)O(7) (x = 0-0.06) and Cs(0.7)Ti(1.8-x)Nb(x)O(4) (x = 0-0.03), were for the first time synthesized by a novel sol-gel assisted solid state reaction (SASSR) route. Conventional solid state reactions as well as sol-gel synthesis did not succeed in producing phase pure Nb-substituted titanates. In the SASSR synthesis route we combine the advantages of traditional sol-gel technique (i.e., homogeneous products formed at low temperatures) and solid state reaction (i.e., formation of stable, crystalline phases) for preparing single-phase niobium-substituted layered titanates. The obtained products were characterized by X-ray powder diffraction, scanning electron microscopy, inductively coupled plasma-atomic emission spectrometry, Raman spectroscopy, and thermogravimetric analysis. Results indicate that the Ti(IV) in the host layer of the samples could be partially replaced by Nb(V) without structural deterioration. After proton-exchange, more water molecules were intercalated into the interlayer of H(0.7)Ti(1.8-x)Nb(x)O(4) x nH(2)O with increasing niobium content, whereas the interlayer distance of H(2)Ti(3-x)Nb(x)O(7) (x = 0-0.06) was unchanged.

An Unusually Acidic and Thermally Stable Cesium Titanate CsxTi2–yMyO4 (x = 0.67 or 0.70; M = vacancy or Zn)

“…Using the full width at half-maximum of the 020 peak and the Scherrer equation, an almost identical crystallite size D was obtained (42 nm for Cs 0.7 TO and 38 nm for Cs 0.7 TO-NH 3 ), also indicating minimal structural changes. In addition, the Raman spectra of the two samples shown in Figure a are generally similar and show bands characteristic , of the lepidocrocite-type cesium titanate. These bands are typically assigned to the Ti–O stretching vibration of the layers. , The preservation of the peak at 914–917 cm –1 due to Cs–O stretching , in particular suggests that Cs + ions persist in a similar local environment, either prior to or after the NH 3 TPD measurement.…”

“…In addition, the Raman spectra of the two samples shown in Figure a are generally similar and show bands characteristic , of the lepidocrocite-type cesium titanate. These bands are typically assigned to the Ti–O stretching vibration of the layers. , The preservation of the peak at 914–917 cm –1 due to Cs–O stretching , in particular suggests that Cs + ions persist in a similar local environment, either prior to or after the NH 3 TPD measurement.…”

“…Taking Cs 0.7 TO as an example, we used CellCalc 35 Using the full width at half-maximum of the 020 peak and the Scherrer equation, an almost identical crystallite size D was obtained (42 nm for Cs 0.7 TO and 38 nm for Cs 0.7 TO-NH 3 ), also indicating minimal structural changes. In addition, the Raman spectra of the two samples shown in Figure 3a are generally similar and show bands characteristic 39,40 of the lepidocrocite-type cesium titanate. These bands are typically assigned to the Ti−O stretching vibration of the layers.…”

“…These bands are typically assigned to the Ti−O stretching vibration of the layers. 39,40 The preservation of the peak at 914−917 cm −1 due to Cs−O stretching 39,40 in particular suggests that Cs + ions persist in a similar local environment, either prior to or after the NH 3 TPD measurement.…”

Structural and Compositional Characteristics of Ball-Milled Lepidocrocite Alkali Titanate and the Correlation to Its Surface Acidic–Basic Properties

“…While the correlation between these two (crystal structure and the preferred orientation) is apparent, the local structure according to Raman spectroscopy remains unaltered. Figure S3 shows that all samples display the band characteristics of the lepidocrocite-type cesium titanate, , where neither the peak positions nor the peak widths/shapes significantly change.…”