A solid solution between polar perovskite oxides BiInO₃ and BiZn_1/2Ti_1/2O₃ with the atomic displacement of Bi³⁺ and B-site (In and Zn_1/2Ti_1/2) as the origin of spontaneous electric polarization was investigated. Polar orthorhombic to nonpolar orthorhombic transition accompanied by negative thermal expansion (NTE) with constant volume shrinkage was observed for x ≤ 0.3 in BiIn_1–x Zn _x/2Ti _x/2O₃. A relative shift of electrical polarization from A-site Bi³⁺ to B-site ions reduced the transition temperature and enabled NTE in a wide temperature range with suppressed temperature hysteresis. In addition, new LiNbO₃-type phases were found for 0.4 ≤ x ≤ 0.8 with ferroelastic and piezoelectric behaviors, featuring a very high switching strain and demonstrating the potential for enhanced domain wall mobility.