The layered double hydroxide (LDH) of Zn with Ga: Synthesis and reversible thermal behaviour

The carbonate containing layered double hydroxide (LDH) of Zn with Ga, crystallizes in an ordered 3R1 polytype having the rhombohedral structure with a fixed composition corresponding to [Zn2+]/[Ga3+] = 2.0. The sulphate containing LDH on the other hand crystallizes in the turbostratically disordered ‘11 Å’ phase. The layered structure collapses at 400 °C. The oxide residue obtained from the carbonate containing LDH has the wurtzite structure with Ga3+ occupying the Zn2+ sites. The defect wurtzite is metastable and reconstructs the LDH either on standing in a water saturated humidity chamber or on soaking in a Na2CO3 solution. The oxide residue obtained from the sulphate containing LDH has an unspecified structure and also reconstructs back into the original LDH on soaking in a Na2SO4 solution. However on heating to 800 °C, spinel (ZnGa2O4) formation is observed subsequent to which the reversible thermal behaviour is lost.

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