Soft-chemical routes to synthesis of solid oxide materials

Abstract

We describe three different families of metal oxides, viz., (i) protonated layered perovskites, (ii) framework phosphates of NASICON and KTiOPO₄ (KTP) structures and (iii) layered and three-dimensional oxides in the H-V-W-O system, synthesized by 'soft-chemical' routes involving respectively ion-exchange, redox deintercalation and acid-leaching from appropriate parent oxides. Oxides of the first family, H_yA₂B₃O₁₀(A = La/Ca; B = Ti/Nb), exhibit variable Bronsted acidity and intercalation behaviour that depend on the interlayer structure. V₂(PO₄)₃ prepared by oxidative deintercalation from Na₃ V₂(PO₄)₃ is a new host material exhibiting reductive insertion of lithium/hydrogen, while K_0.5Nb_0.5 M_0.5OPO₄ (M = Ti, V) are novel KTP-like materials exhibiting second harmonic generation of 1064nm radiation. H_xV_xW_1-xO₃ for x = 0·125 and 0·33 possessing α-MoO₃ and hexagonal WO₃ structures, prepared by acid-leaching of LiVWO₆, represent functionalized oxide materials exhibiting redox and acid-base intercalation reactivity.