  We report thermal-expansion, lattice-constant, and specific-heat data of the
series La_1-xA_xCoO_3 for 0<= x <= 0.30 with A = Ca, Sr, and Ba. For the
undoped compound LaCoO_3 the thermal-expansion coefficient alpha(T) exhibits a
pronounced maximum around T=50K caused by a temperature-driven spin-state
transition from a low-spin state of the Co^{3+$ ions at low towards a higher
spin state at higher temperatures. The partial substitution of the La^{3+} ions
by divalent Ca^{2+}, Sr^{2+}, or Ba^{2+} ions causes drastic changes in the
macroscopic properties of LaCoO3. The large maximum in alpha(T) is suppressed
and completely vanishes for x> 0.12. For A = Ca three different anomalies
develop in alpha(T) with further increasing x, which are visible in
specific-heat data as well. Together with temperature-dependent x-ray data we
identify several phase transitions as a function of the doping concentration x
and temperature. From these data we propose an extended phase diagram for
La_1-xCa_xCoO_3.
