High piezoelectric properties are desired for lead-free piezoelectric materials in consideration as a replacement for lead-based materials in applications. Due to the high piezoelectric coefficient, (Ba100-xCax) (Ti100-yZry) O-3 (BCTZ) piezoelectric ceramics have been considered as a promising lead-free alternate piezoelectric material. Here, six compositions were selected based on a prediction that all the compositions would have high piezoelectric coefficient at room temperature. The results confirmed all compositions exhibit well developed hysteresis loops and a large piezoelectric coefficient at room temperature. This is due to the coexistence of several phases where the major phase is likely to be orthorhombic and the second phase is proposed to be tetragonal. The phase transition was found to occur over a broad temperature range instead of at a specific temperature only. A relationship between the tetragonal-orthorhombic phase transition temperature and Ca2+ and Zr4+ content was proposed. This enables clear determination of BCTZ compositions with high piezoelectric coefficient at a desired operation temperature.