Neutron powder diffraction experiments have been carried out on two in
teresting perovskite compounds, Sr2RuO4 (K2NiF4 structure) and SrRuO3
(distorted perovskite), both of which are used as substrates for the g
rowth of high-temperature superconducting thin films. The powder diffr
action data have been refined at high and low temperatures to obtain l
attice parameters and the lattice mismatch between these compounds and
YBa2Cu3O7 over a wide temperature range is found to be good. No evide
nce has been found for any lattice distortions between 5 and 973 K in
Sr2RuO4 and between 100 and 300 K in SrRuO3.