Open following file,
Applications > Accessories > Terminal
sudo gedit /etc/koha/zebradb/etc/default.idx
Find the line "charmap word-phrase-utf.chr" and comment it by inserting a # symbol. The same line appeared in next paragraph too, do the same.
charmap word-phrase-utf.chr
# Phrase index
# Used if completeness is 'complete {sub}field' (@attr 6=2, @attr 6=1)
# and structure is word/phrase/word-list/free-form-text/document-text
index p
completeness 1
firstinfield 1
charmap word-phrase-utf.chr
Make changes like this commenting lines and adding following line
#charmap word-phrase-utf.chr
icuchain words-icu.xml
# Phrase index
# Used if completeness is 'complete {sub}field' (@attr 6=2, @attr 6=1)
# and structure is word/phrase/word-list/free-form-text/document-text
index p
completeness 1
firstinfield 1
#charmap word-phrase-utf.chr
icuchain words-icu.xml
Rebuild zebra
sudo koha-rebuild-zebra -v -f library
Information courtesy: Bhaskar Ghosh, Gurudas College, Phoolbagan, West Bengal.