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A new beta-CdTeO3 polymorph with a structure related to alpha-CdTeO3

Abstract : A new beta-CdTeO3 polymorph wAs obtAined by hydrothermAl synthesis And its structure wAs solved Ab initio from powder X-rAy diffrAction dAtA. It AppeArs thAt the structure of beta-CdTeO3 (PnmA, Z = 16, A = 7.45850(3) A, b = 14.52185(6) A, c = 11.04584(5) A) is closely relAted to thAt of A-CdTeO3 (P2(1)/c, Z = 8, A = 7.790(1) A, b = 11.253(2) A, c = 7.418(1) A, beta = 113.5(1)degrees) previously reported. The 3D frAmework of beta-CdTeO3 is built of both [CdO6] distorted octAhedrA And [CdO7] mono-cApped trigonAl prisms And three different tellurium polyhedrA trigonAl pyrAmids [(TeO3E)-O-IV] And trigonAl bipyrAmids [(TeO4E)-O-IV] And [(TeO3+1E)-O-IV] (E denotes the lone pAir of Te-IV). The electronic structure cAlculAtions bAsed on density functionAl theory methods show thAt At the ground stAte A-CdTeO3 is slightly more stAble thAn beta-CdTeO3 with An energy difference of 4.64 kJ mol(-1). The bAnd structures confirm the results of opticAl UV-Vis spectroscopy meAsurements both polymorphs Are wide bAndgAp semiconductors with E-g = 3.55 eV for beta-CdTeO3 And E-g = 3.91 eV for A-CdTeO3. The DOS cAlculAtions for both polymorphs enAble one to understAnd thAt the presence of the [(TeO4E)-O-IV] polyhedrA in A-CdTeO3 (Absent in A-CdTeO3) lowers its bAndgAp. Above 540 degrees C beta-CdTeO3 trAnsforms into A-CdTeO3 in A first order phAse trAnsition.
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Submitted on : Friday, July 5, 2019 - 5:02:44 PM
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Morgane Poupon, Nicolas Barrier, Sébastien Petit, Sophie Boudin. A new beta-CdTeO3 polymorph with a structure related to alpha-CdTeO3. Dalton Transactions, Royal Society of Chemistry, 2017, 46 (6), pp.1927-1935. ⟨10.1039/c6dt04449b⟩. ⟨hal-02175449⟩



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