Al~(3+)/Mo~(6+)双离子取代ZrV_2O_7中Zr~(4+)/V~(5+)实现近零膨胀

采用固相烧结法制备了Zri_(1-x)Al_(2-x)V_(2-x)Mo_xO_7(0≤x≤0.9),并通过调整Al~(3+)/Mo~(6+)对ZrV_2O_7中的Zr~(4+)/V~(5+)离子替代量来实现近零膨胀,对于较小的x值(x≤0.3),材料保持了与ZrV_2O_7相同的立方相结构.随着Al~(3+)/Mo~(6+)替代量的增加,(Al/Zr)~-和(Mo/V)~+之间的库仑相互作用逐渐加强,这种库仑相互作用导致材料中未发生畸变的立方相晶体结构逐渐减少.当x≥0.7时,材料中立方相晶体结构完全消失.在425-750 K温度区间内,Zr_(0.5)Al_(0.5)M_(0.6)O_7展示出近零膨胀性质(-0.39×l0~(-6)K~(-1)).Zr_(0.5)Al_(1.5)V_(1.5)Mo_(0.5)O_7的低热膨胀性能可能与Al~(3+)/Mo~(6+)对ZrV_2O_7中Zr~(4+)/V~(5+)部分替代引起部分晶体结构发生的畸变及其对未替代部分的晶格结构的影响有关.

Substitutions of dual-ion Al3+/Mo6+ for Zr4+/V5+ in ZrV2O7 for realizing near-zero thermal expansion

Zr_1-xAl_xV_2-xMo_xO₇ (0 ≤ x ≤ 0.9) is developed by the solid state method, and the near-zero thermal expansion is realized by adjusting the quantity of substitution of Al³⁺/Mo⁶⁺ for Zr⁴⁺/V⁵⁺ in ZrV₂O₇. For smaller x values (x ≤ 0.3), the samples remain the same cubic structure as that of ZrV₂O₇. The Coulomb interaction between (Al/Zr)^- and (Mo/V)⁺ increases gradually with increasing the quantity of dual-ion substitution of Al³⁺/Mo⁶⁺ for Zr⁴⁺/V⁵⁺ in ZrV₂O₇, which reduces the fraction of the distortionless cubic structure in the sample. For x ≥ 0.7, the cubic structures could not be found. For Zr_0.5Al_0.5V_1.5Mo_0.5O₇, near-zero thermal expansion is obtained in a temperature range from 425 to 750 K (-0.39×10^-6 K^-1). The mechanism of low thermal expansion of Zr_0.5Al_0.5V_1.5Mo_0.5O₇ could relate to the distortion of crystal structure due to partial substitution of Al³⁺/Mo⁶⁺ for Zr⁴⁺/V⁵⁺ in ZrV₂O₇ and the effect of the substitution on the unsubstituted lattice.