EARTH

[3913-23-08] Synthesis and utilization of Zn-rare earth layered double hydroxides

○Ayumi Tsuda¹, Mituaki Matsuoka¹, Norihiro Murayama¹ (1. Kansai University)

司会（Chairman）：Carlito Tabelin （Hokkaido University）

キーワード：Layered double hydroxide, Rare earth, Composite oxide

Layered double hydroxide (LDH) is one of inorganic compounds having ion exchange ability. The general formula is represented by [M²⁺_1-xM³⁺_x(OH)₂]^x+[A^n-_x/n･mH₂O]^x-. M²⁺ and M³⁺ are divalent and trivalent metal ions, respectively, and A^n- is also an n-valent anion. There are many LDHs composed of transition metals, but little has been done to synthesize the LDHs containing rare earths. For example, rare earth LDH is attracting attention to visualization in the body as a drug delivery material utilizing the fluorescence characteristics of rare earth elements. In addition, there is a possibility to apply them to catalysts and optoelectronic materials etc. Furthermore, using the LDH as a precursor of complex oxide may contribute to lower temperature to obtain the calcinations products.
In this study, the synthesis method of LDH containing Sm for trivalent metal ion, Zn for divalent metal ion and CO₃^2- for anions in LDH were conducted by a co-precipitation method. The resulting products were characterized by XRD, SEM etc. They were also discussed in terms of the physical property of CO₃^2- type Zn-Al LDH.
When Na₂CO₃ as a buffer solution was heated at 55 °C or higher and a mixed solution prepared with [Zn^{2 +}] / [Sm^{3 +}] = 1: 2 was added, the XRD patterns of the obtained precipitates were confirmed due to the formation of layered compounds. When the heating temperature of buffer solution was set to be 60 °C, the intensity of XRD caused by the layered compounds showed the highest. Over 60 °C, the intensity decreased with an increase in heating temperature. Important factor to synthesize the rare earth LDH was found to be the heating process of buffer solution to get precipitates. It was also suggested that the use of these LDHs makes it possible to synthesize oxides at low temperatures.