Dependence of the Lattice Parameter of Magnesium Oxide on Crystallite Size

Abstract

Lattice parameters were measured on MgO specimens prepared in air between 450' and 1200'C. The lattice parameter, a, decreases with increase in preparation temperature, T,,, and with increase in crystallite size. A hydroxide layer is present on the MgO particles. If MgO is prepared in vacuum, a increases as T,, increases and as+ crystallite size, D, increases. It is concluded that a dilatant volume stress is imposed by the hy&oxide layer. It is also shown that the oxide surface reactivity toward water is linked to the deviation from perfect order ensuing from low preparation temperatures.

Highly defective MgO nanosheets from colloidal self-assembly

“…A possible cause for the increased lattice parameter in the as prepared NSs could be a high concentration of point defects, such as vacancies or interstitial atoms, like hydrogen, which would correspond to hydroxyl groups trapped within the lattice. 23 The Fourier-filtered HR-TEM image in Fig. 4a reveals that the NSs are highly defective.…”

Small metal particles

“…Постоянная решетки у кластера с диаметром практически такой же, как у массивного металла, и только при диаметре она уменьшена на 2 %. В некоторых случаях наблюдается растяжение частиц вместо их сжатия [60][61][62][63]107] (рис. 4).…”

“…Малые частицы алмаза и кремния тоже растягиваются [229,230]. Согласно [60] частица MgO с чистой поверхностью сжимается, а после адсорбции на ней гидроокиси она растягивается. Существует много при чин, по которым деформация частицы зависит от адсорбции: из за нее меняются поверхностные напряжения, релаксация и т.д.…”

Thickness Effect on Fluctuation of Electron States in Thin Film and Implications for Lattice Constant Change Due to Size Reduction

“…When either expansion or contraction is observed, some materials show only contraction or expansion, and some materials show both expansion and contraction, measured relative to the corresponding parameters in the bulk state. Expansion of the lattice parameter is generally observed in oxides such as CeO 2 [4][5][6], Fe 2 O 3 [7], MgO [8], TiO 2 (rutile) [9], ZrO 2 [10], BaTiO 3 [11], cubic PbTiO 3 [12], and BiFeO 3 [13]. In contrast, contraction in the lattice parameter, is observed in most metals, such as Au [14][15][16], Ag [17][18][19][20], Sn [21], Bi [21,22], Pt [15,23], Si [24], Cu [25], Ni [25], Pd [26,27], ZnS and CdSe [28,29].…”