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Ba 2 Zn (1+ x ) Si 2 O (7+ x ) ceramics were prepared using the conventional solid-state method at 1200 °C for 3 h in air. Apart from the previously reported Ba 2 Zn (1+ x ) Si 2 O (7+ x ) ( x = 0) with a monoclinic structure ( C 2/c ), the end-member compositions at x = −1 and 1 exhibit single-phase β -BaSiO 3 with an orthorhombic structure ( P 2 1 2 1 2 1 ) and BaZnSiO 4 with a hexagonal structure ( P 6 3 ), and possess a coexistence of weak ferroelectricity and low-permittivity microwave dielectric properties. A reduction in Zn 2+ content mainly decreases the intensity of the ε r anomaly peak at lower temperature and increases the ε r (or frequency) stability against temperature. The Zn 2+ -rich BaZnSiO 4 phase has a τ f value of −181 ppm/°C, whereas the τ f value of Zn 2+ -free BaSiO 3 phase decreases to −35.4 ppm/°C. The Zn 2+ deficiency in Ba 2 ZnSi 2 O 7 composition could inhibit the presence of BaZnSiO 4 phase and improve the τ f value, whereas excessive Zn 2+ cations prompt the formation of the BaZnSiO 4 phase to deteriorate significantly the τ f value. [ABSTRACT FROM AUTHOR]