(a) Effect of relativistic parameter along with the influence of positive ion temperature on the solitary wave amplitude, (b) variation of wave amplitude with the relativistic effect for different ratios of negative ion temperature (T_n) to positive ions temperature (T_p). Here, m_p = 40 × 10⁻²⁷ kg (argon positive ion), m_n = 16 × 10⁻²⁷ kg (oxygen negative ion), m_d = 10⁻¹⁸ kg, dust temperature, T_d = 0.06 eV, n_e0 = 3.8 × 10¹⁴, n_p0 = 5.5 × 10¹⁴, n_n0 = 0.3 × 10¹⁴, n_d0 = 2 × 10¹⁰, v₀ = 1, z_d0 = 1.5 × 10⁴e, and r_d = 2.0 × 10⁻⁶ m. The dash line is for T_n = 0.5T_p, the solid line is for T_n = T_p, and the dash–dotted line is for T_n = 2T_p.